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Journal articles on the topic 'Transcobalamina'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Ulleland, Marius, Ingar Eilertsen, Edward V. Quadros, Sheldon P. Rothenberg, Sergey N. Fedosov, Erling Sundrehagen, and Lars Örning. "Direct Assay for Cobalamin Bound to Transcobalamin (Holo-Transcobalamin) in Serum." Clinical Chemistry 48, no. 3 (March 1, 2002): 526–32. http://dx.doi.org/10.1093/clinchem/48.3.526.

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Abstract Background: Only cobalamin carried by transcobalamin (holo-transcobalamin) is available for cellular uptake and hence is physiologically relevant. However, no reliable or accurate methods for quantifying holo-transcobalamin are available. We report a novel holo-transcobalamin assay based on solid-phase capture of transcobalamin. Methods: A monoclonal antibody specific for human transcobalamin with an affinity constant >1010 L/mol was immobilized on magnetic microspheres to capture and concentrate transcobalamin. The cobalamin bound to transcobalamin was then released and assayed by a competitive binding radioassay. The quantification of holo-transcobalamin was accomplished using calibrators composed of recombinant, human holo-transcobalamin. Results: The assay was specific for holo-transcobalamin and had a detection limit of 5 pmol/L. Within-run and total imprecision (CV) was 5% and 8–9%, respectively. The working range (CV <20%) was 5–370 pmol/L. Dilutions of serum were linear in the assay range. The recovery of recombinant, human holo-transcobalamin added to serum was 93–108%. A 95% reference interval of 24–157 pmol/L was established for holo-transcobalamin in 105 healthy volunteers 20–80 years of age. For 72 of these sera, holo-haptocorrin and total cobalamin were also determined. Whereas holo-haptocorrin correlated well (r2 = 0.87) with total cobalamin, holo-transcobalamin correlated poorly (r2 = 0.23) with total cobalamin or holo-haptocorrin. Conclusions: The solid-phase capture assay provides a simple, reliable method for quantitative determination of holo-transcobalamin in serum.

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2

Nexo, Ebba, Anna-Lisa Christensen, Torben E. Petersen, and Sergey N. Fedosov. "Measurement of Transcobalamin by ELISA." Clinical Chemistry 46, no. 10 (October 1, 2000): 1643–49. http://dx.doi.org/10.1093/clinchem/46.10.1643.

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Abstract Background: Transcobalamin is essential for the cellular internalization of cobalamin. Methods to quantify the unsaturated protein are available, but few attempts have been made to develop methods to quantify the sum of unsaturated and cobalamin saturated transcobalamin. Methods: γ-Globulins from two polyclonal rabbit antibodies against recombinant human transcobalamin were used as capture and detection antibodies, and recombinant human transcobalamin was used as calibrator in an ELISA design. Results: The ELISA is specific for transcobalamin and has a detection limit of <1.6 pmol/L. The imprecision (CV) is 4–6% for mean concentrations of 13–70 pmol/L. The central 95% interval for serum from healthy blood donors (n = 77) was ∼600-1500 pmol/L and showed limited variation with age and sex. No correlation was observed between the marker of acute phase reaction, C-reactive protein, and transcobalamin in plasma. Conclusions: The ELISA measures total transcobalamin in serum and thus can be used for measurement of transcobalamin in patients treated with cobalamin.

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3

Uchiyama, Yukinobu. "Transcobalamin deficiency." SEIBUTSU BUTSURI KAGAKU 38, no. 6 (1994): 403–10. http://dx.doi.org/10.2198/sbk.38.403.

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4

Carmel, Ralph. "Measuring and Interpreting Holo-Transcobalamin (Holo-Transcobalamin II)." Clinical Chemistry 48, no. 3 (March 1, 2002): 407–9. http://dx.doi.org/10.1093/clinchem/48.3.407.

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5

NIELSEN, RIKKE, BOE SANDAHL SØRENSEN, HENRIK BIRN, ERIK ILSØ CHRISTENSEN, and EBBA NEXØ. "Transcellular Transport of Vitamin B12in LLC-PK1 Renal Proximal Tubule Cells." Journal of the American Society of Nephrology 12, no. 6 (June 2001): 1099–106. http://dx.doi.org/10.1681/asn.v1261099.

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Abstract. The transcobalamin-vitamin B12complex is responsible for the transport of B12from plasma and into the tissues. The complex is filtered in the renal glomeruli and is a high-affinity ligand for the endocytic receptor megalin expressed in the proximal tubule. This study shows by the use of the proximal tubule LLC-PK1 cell line that transcobalamin-B12is internalized by megalin-mediated endocytosis. After endocytosis and accumulation in endosomes, transcobalamin is degraded and the B12molecule is released from the cells in complex with newly synthesized proteins. The release is polarized in such a way that vitamin in the apical medium is bound to proteins with the size of haptocorrin, whereas the B12released at the basolateral side is complexed to two different proteins with the sizes of transcobalamin and haptocorrin. Furthermore, transcobalamin mRNA was identified by reverse transcription-PCR in LLC-PK1 cells and human and pig kidney, whereas haptocorrin mRNA was identified only in LLC-PK1 cells. The results strongly suggest that megalin located in the proximal tubule cells is important for receptor-mediated tubular reabsorption followed by transcellular transport and release of vitamin B12complexed to newly synthesized carrier proteins. This mechanism is likely to play a significant role in the maintenance of B12homeostasis by returning filtered B12to the pool of circulating vitamin.

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6

Hygum, Katrine, Dorte L. Lildballe, Eva H. Greibe, Anne L. Morkbak, Steen S. Poulsen, Boe S. Sorensen, Torben E. Petersen, and Ebba Nexo. "Mouse Transcobalamin Has Features Resembling both Human Transcobalamin and Haptocorrin." PLoS ONE 6, no. 5 (May 31, 2011): e20638. http://dx.doi.org/10.1371/journal.pone.0020638.

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7

Schohn, H., J. L. Guéant, M. Girr, E. Nexø, L. Baricault, A. Zweibaum, and J. P. Nicolas. "Synthesis and secretion of a cobalamin-binding protein by HT 29 cell line." Biochemical Journal 280, no. 2 (December 1, 1991): 427–30. http://dx.doi.org/10.1042/bj2800427.

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An HT 29 cell line derived from human colonic carcinoma was shown to synthesize and release a cobalamin-binding protein. The cobalamin-binding protein was classified as transcobalamin (TC). By gel filtration on Sephacryl S200 HR, we observed that the secreted protein bound to cobalamin had the same size as plasma transcobalamin. Like transcobalamin, the cobalamin-binding protein bound cobalamin but not cobinamide. Purification of the cobalamin-binding protein was performed by heparin-Sepharose affinity chromatography and by Sephacryl S200 gel filtration. The molecular mass of the purified protein was estimated at 44 kDa by SDS/PAGE. The isoelectric point was determined to be 6.4. The purified cobalamin-binding protein reacted with an antiserum produced against human transcobalamin. A 44 kDa band was also identified by SDS/PAGE of an immunoprecipitated homogenate from HT 29 cells labelled with [35S]methionine and in a Western blot of cell homogenates. The secretion of the cobalamin-binding protein was maximal between 10 and 12 days of cell culture and was inhibited by cycloheximide.

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8

van Asselt, Dieneke Z. B., Chris M. G. Thomas, Martin F. G. Segers, Henk J. Blom, Ron A. Wevers, and Willibrord H. L. Hoefnagels. "Cobalamin-binding proteins in normal and cobalamin-deficient older subjects." Annals of Clinical Biochemistry: International Journal of Laboratory Medicine 40, no. 1 (January 1, 2003): 65–69. http://dx.doi.org/10.1258/000456303321016187.

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Background: The causes of cobalamin (vitamin B12) deficiency in older people are only partly understood. We investigated the role of the cobalamin-binding proteins and tested the hypothesis that low saturated transcobalamin concentration is an early marker of cobalamin deficiency. Methods: We measured saturated (holo) and unsaturated (apo) transcobalamin and haptocorrin concentrations in healthy middle-aged volunteers, healthy older volunteers, cobalamin-deficient older volunteers and cobalamin-deficient older patients. Results: Holo and apo concentrations of transcobalamin and haptocorrin were similar in healthy middle-aged and older subjects. Holotranscobalamin concentrations were significantly decreased in cobalamin-deficient subjects but did not differ between healthy volunteers and patients. Furthermore, the relative amount of cobalamin on transcobalamin (i.e. holotranscobalamin/holotranscobalamin + holohaptocorrin) was similar in all four groups. Conclusions: Abnormalities of the cobalamin-binding proteins are not a cause of cobalamin deficiency in the aged. Plasma holotranscobalamin concentration did not differ between stages of cobalamin deficiency in older persons. Therefore, plasma holotranscobalamin is not an early marker of cobalamin deficiency in older people and has no additional value in the diagnostic work-up of reduced plasma cobalamin concentrations in older people.

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9

McCaddon, Andrew, Kaj Blennow, Peter Hudson, Alan Hughes, Joan Barber, Rob Gray, Gareth Davies, et al. "Transcobalamin Polymorphism and Serum Holo-Transcobalamin in Relation to Alzheimer’s Disease." Dementia and Geriatric Cognitive Disorders 17, no. 3 (2004): 215–21. http://dx.doi.org/10.1159/000076359.

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10

Abuyaman, Omar, Niels Torring, Rima Obeid, and Ebba Nexo. "First trimester serum levels of the soluble transcobalamin receptor, holo-transcobalamin, and total transcobalamin in relation to preeclampsia risk." Scandinavian Journal of Clinical and Laboratory Investigation 76, no. 8 (October 4, 2016): 641–44. http://dx.doi.org/10.1080/00365513.2016.1230885.

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11

Carmel, Ralph, Shabneet Brar, and Zohreh Frouhar. "Plasma Total Transcobalamin I." American Journal of Clinical Pathology 116, no. 4 (October 2001): 576–80. http://dx.doi.org/10.1309/l6q9-68e7-3284-6d1k.

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12

McCaddon, Andrew, Kaj Blennow, Peter Hudson, Björn Regland, and Diane Hill. "Transcobalamin polymorphism and homocysteine." Blood 98, no. 12 (December 1, 2001): 3497–500. http://dx.doi.org/10.1182/blood.v98.12.3497.

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13

Jacobsen, Donald W., and Alla V. Glushchenko. "The transcobalamin receptor, redux." Blood 113, no. 1 (January 1, 2009): 3–4. http://dx.doi.org/10.1182/blood-2008-10-181750.

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14

Rothenberg, Sheldon P., and Edward V. Quadros. "4 Transcobalamin II and the membrane receptor for the transcobalamin II-cobalamin complex." Baillière's Clinical Haematology 8, no. 3 (September 1995): 499–514. http://dx.doi.org/10.1016/s0950-3536(05)80218-5.

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15

Rachmilewitz, Bracha, Noga Manny, and Moshe Rachmilewitz. "The Transcobalamins in Polycythaemia Vera." Scandinavian Journal of Haematology 19, no. 5 (April 24, 2009): 453–62. http://dx.doi.org/10.1111/j.1600-0609.1977.tb01501.x.

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16

Ratschmann, Rene, Milen Minkov, Ana Kis, Christina Hung, Tony Rupar, Adolf Mühl, Brian Fowler, Ebba Nexo, and Olaf A. Bodamer. "Transcobalamin II deficiency at birth." Molecular Genetics and Metabolism 98, no. 3 (November 2009): 285–88. http://dx.doi.org/10.1016/j.ymgme.2009.06.003.

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17

Bose, Santanu, Jimmy Feix, Shakuntla Seetharam, and Bellur Seetharam. "Dimerization of Transcobalamin II Receptor." Journal of Biological Chemistry 271, no. 20 (May 17, 1996): 11718–25. http://dx.doi.org/10.1074/jbc.271.20.11718.

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18

Nexø, Ebba. "Characterization of the Cobalamins Attached to Transcobalamin I and Transcobalamin II in Human Plasma." Scandinavian Journal of Haematology 18, no. 5 (April 24, 2009): 358–60. http://dx.doi.org/10.1111/j.1600-0609.1977.tb02089.x.

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19

Li, N., S. Seetharam, and B. Seetharam. "Genomic Structure of Human Transcobalamin II: Comparison to Human Intrinsic Factor and Transcobalamin I." Biochemical and Biophysical Research Communications 208, no. 2 (March 1995): 756–64. http://dx.doi.org/10.1006/bbrc.1995.1402.

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20

Pavlov, Ch S., I. V. Damulin, Yu O. Shulpekova, and E. A. Andreev. "Neurological disorders in vitamin B12 deficiency." Terapevticheskii arkhiv 91, no. 4 (April 15, 2019): 122–29. http://dx.doi.org/10.26442/00403660.2019.04.000116.

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The review discusses thesteps of vitamin B12 metabolism and its role in maintaining of neurological functions. The term "vitamin B12 (cobalamin)" refers to several substances (cobalamins) of a very similar structure. Cobalamin enters the body with animal products. On the peripherу cobalamin circulates only in binding with proteins transcobalamin I and II (complex cobalamin-transcobalamin II is designated as “holotranscobalamin”). Holotranscobalamin is absorbed by different cells, whereas transcobalamin I-binded vitamin B12 - only by liver and kidneys. Two forms of cobalamin were identified as coenzymes of cellular reactions which are methylcobalamin (in cytoplasm) and hydroxyadenosylcobalamin (in mitochondria). The main causes of cobalamin deficiency are related to inadequate intake of animal products, autoimmune gastritis, pancreatic insufficiency, terminal ileum disease, syndrome of intestinal bacterial overgrowth. Relative deficiency may be seen in excessive binding of vitamin B12 to transcobalamin I. Cobalamin deficiency most significantly affects functions of blood, nervous system and inflammatory response. Anemia occurs in 13-15% of cases; macrocytosis is an early sign. The average size of neutrophils and monocytes is the most sensitive marker of megaloblastic hematopoiesis. The demands in vitamin B12 are particularly high in nervous tissue. Hypovitaminosis is accompanied by pathological lesions both in white and gray brain matter. Several types of neurological manifestations are described: subacute combined degeneration of spinal cord (funicular myelinosis), sensomotor polyneuropathy, optic nerve neuropathy, cognitive disorders. The whole range of neuropsychiatric disorders with vitamin B12 deficiency has not been studied well enough. Due to certain diagnostic difficulties they are often regarded as "cryptogenic", "reactive", "vascular» origin. Normal or decreased total plasma cobalamin level could not a reliable marker of vitamin deficiency. In difficult cases the content of holotranscobalamin, methylmalonic acid / homocysteine, and folate in the blood serum should be investigated besides carefully analysis of clinical manifestations.

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21

Frémont, S., B. Champigneulle, P. Gérard, F. Felden, D. Lambert, J. L. Guéant, and J. P. Nicolas. "Blood Transcobalamin Levels in Malignant Hepatoma." Tumor Biology 12, no. 6 (1991): 353–59. http://dx.doi.org/10.1159/000217736.

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22

Rosenblatt, David S., Angela Hosack, and Nora Matiaszuk. "Expression of transcobalamin II by amniocytes." Prenatal Diagnosis 7, no. 1 (January 1987): 35–39. http://dx.doi.org/10.1002/pd.1970070107.

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23

Dharmasena, Aruna. "Retinopathy in Inherited Transcobalamin II Deficiency." Archives of Ophthalmology 126, no. 1 (January 1, 2008): 141. http://dx.doi.org/10.1001/archophthalmol.2007.21.

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24

Schiff, Manuel, Hélène Ogier de Baulny, Ghislaine Bard, Vincent Barlogis, Christian Hamel, Stuart J. Moat, Sylvie Odent, Graham Shortland, Guy Touati, and Stéphane Giraudier. "Should transcobalamin deficiency be treated aggressively?" Journal of Inherited Metabolic Disease 33, no. 3 (March 30, 2010): 223–29. http://dx.doi.org/10.1007/s10545-010-9074-x.

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25

Prasad, Chitra, A. E. Cairney, D. S. Rosenblatt, and C. A. Rupar. "Transcobalamin (TC) deficiency and newborn screening." Journal of Inherited Metabolic Disease 35, no. 4 (December 14, 2011): 727. http://dx.doi.org/10.1007/s10545-011-9431-4.

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26

Carmel, Ralph. "Haptocorrin (Transcobalamin I) and Cobalamin Deficiencies." Clinical Chemistry 53, no. 2 (February 1, 2007): 367–68. http://dx.doi.org/10.1373/clinchem.2006.078808.

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27

Hashemi, Mohammad, Mojgan Mokhtari, Vajiheh Yazdani-Shahrbabaki, Hiva Danesh, Fatemeh Bizhani, and Mohsen Taheri. "Evaluation of transcobalamin II rs1801198 and transcobalamin II receptor rs2336573 gene polymorphisms in recurrent spontaneous abortion." Journal of Obstetrics and Gynaecology 38, no. 6 (March 14, 2018): 860–63. http://dx.doi.org/10.1080/01443615.2017.1420045.

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28

Wuerges, Jochen, Silvano Geremia, and Lucio Randaccio. "Structural study on ligand specificity of human vitamin B12 transporters." Biochemical Journal 403, no. 3 (April 12, 2007): 431–40. http://dx.doi.org/10.1042/bj20061394.

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Studies comparing the binding of genuine cobalamin (vitamin B12) to that of its natural or synthetic analogues have long established increasing ligand specificity in the order haptocorrin, transcobalamin and intrinsic factor, the high-affinity binding proteins involved in cobalamin transport in mammals. In the present study, ligand specificity was investigated from a structural point of view, for which comparative models of intrinsic factor and haptocorrin are produced based on the crystal structure of the homologous transcobalamin and validated by results of published binding assays. Many interactions between cobalamin and its binding site in the interface of the two domains are conserved among the transporters. A structural comparison suggests that the determinant of specificity regarding cobalamin ligands with modified nucleotide moiety resides in the β-hairpin motif β3-turn-β4 of the smaller C-terminal domain. In haptocorrin, it provides hydrophobic contacts to the benzimidazole moiety through the apolar regions of Arg357, Trp359 and Tyr362. Together, these large side chains may compensate for the missing nucleotide upon cobinamide binding. Intrinsic factor possesses only the tryptophan residue and transcobalamin only the tyrosine residue, consistent with their low affinity for cobinamide. Relative affinity constants for other analogues are rationalized similarly by analysis of steric and electrostatic interactions with the three transporters. The structures also indicate that the C-terminal domain is the first site of cobalamin-binding since part of the β-hairpin motif is trapped between the nucleotide moiety and the N-terminal domain in the final holo-proteins.

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29

Afman, Lydia A., Karin J. A. Lievers, Nathalie M. J. van der Put, Frans J. M. Trijbels, and Henk J. Blom. "Single nucleotide polymorphisms in the transcobalamin gene: relationship with transcobalamin concentrations and risk for neural tube defects." European Journal of Human Genetics 10, no. 7 (July 2002): 433–38. http://dx.doi.org/10.1038/sj.ejhg.5200830.

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30

Bor, Mustafa Vakur, Ebba Nexø, and Anne-Mette Hvas. "Holo-Transcobalamin Concentration and Transcobalamin Saturation Reflect Recent Vitamin B12 Absorption Better than Does Serum Vitamin B12." Clinical Chemistry 50, no. 6 (June 1, 2004): 1043–49. http://dx.doi.org/10.1373/clinchem.2003.027458.

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Abstract Background: We evaluated whether measurement of vitamin B12-saturated transcobalamin (holo-TC) concentrations or TC saturation (holo-TC:total TC) reflects active vitamin B12 absorption in healthy individuals and patients after vitamin B12 intake. Methods: We obtained blood samples from 31 healthy individuals (age range, 25–57 years) before (days −1 and 0) and after (days 1, 2, and 6) oral administration of three 9-μg doses of vitamin B12. The blood samples from seven patients (age range, 22–39 years) suspected to have decreased vitamin B12 absorption were obtained before and 1 day after the vitamin B12 intake. The blood samples were analyzed for vitamin B12, total TC, and holo-TC. The TC saturation was calculated. Results: Intraindividual variation was <13% for all measured values, as calculated from samples removed on day −1 and 0. In healthy individuals (n = 31) after intake of vitamin B12, the maximum median (range) increase (as percentages and absolute values) was in TC saturation [52 (−2% to 128)% and 0.04 (0–0.23) as a fraction], closely followed by holo-TC concentrations [39 (0–108)% and 34 (0–149) pmol/L]. All but one healthy individual had an increase of ≥15% in these markers. Serum vitamin B12 showed a smaller increase [14 (−8 to 51)% and 36 (−27 to 290) pmol/L]. After vitamin B12 intake, three patients with Crohn disease had the lowest increases in holo-TC concentration (3, 7, and 14 pmol/L) and in TC saturation (0.004, 0.01, and 0.01) among patients and 30 healthy individuals. Conclusion: Holo-TC concentrations and TC saturation reflect normal vitamin B12 absorption better than does serum vitamin B12.

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31

Carter, Margaret, Cun Li, Darren Farley, Donald Dudley, and Peter Nathanielsz. "200: Regulation of folate receptor, transcobalamin II, and transcobalamin II receptor in the placenta of obese women." American Journal of Obstetrics and Gynecology 201, no. 6 (December 2009): S87. http://dx.doi.org/10.1016/j.ajog.2009.10.215.

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32

Lildballe, Dorte L., Sergey Fedosov, Paul Sherliker, Harold Hin, Robert Clarke, and Ebba Nexo. "Association of Cognitive Impairment with Combinations of Vitamin B12–Related Parameters." Clinical Chemistry 57, no. 10 (October 1, 2011): 1436–43. http://dx.doi.org/10.1373/clinchem.2011.165944.

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BACKGROUND Low vitamin B12 concentrations have been associated with higher risks of cognitive impairment, but whether these associations are causal is uncertain. The associations of cognitive impairment with combinations of vitamin B12, holotranscobalamin, methylmalonic acid, and total homocysteine, and with the vitamin B12 transport proteins transcobalamin and haptocorrin, have not been previously studied. METHODS We performed a population-based cross-sectional study of 839 people 75 years old or older. We examined the association of cognitive function as measured by mini–mental state examination scores, with markers of vitamin B12 status. Spearman correlations as well as multivariate-adjusted odds ratios and 95% CIs for cognitive impairment were calculated for extreme thirds of serum concentrations of vitamin B12, holotranscobalamin, methylmalonic acid, total homocysteine, combination of these markers in a wellness score, heaptocorrin, and transcobalamin for all data and with B12 analogs in a nested case-control study. RESULTS Cognitive impairment was significantly associated with low vitamin B12 [odds ratio 2.3 (95% CI 1.2–4.5)]; low holotranscobalamin [4.1 (2.0–8.7)], high methylmalonic acid [3.5 (1.8–7.1)], high homocysteine [4.8 (2.3–10.0)] and low wellness score [5.1 (2.61–10.46)]. After correction for relevant covariates, cognitive impairment remained significantly associated with high homocysteine [4.85 (2.24–10.53)] and with a low wellness score [5.60 (2.61–12.01)] but not with transcobalamin, haptocorrin, or analogs on haptocorrin. CONCLUSIONS Cognitive impairment was associated with the combined effects of the 4 biomarkers of vitamin B12 deficiency when included in a wellness score but was not associated with binding proteins or analogs on haptocorrin.

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33

Benoit, Courtney R., Darren J. Walsh, Levan Mekerishvili, Nadia Houerbi, Abigail E. Stanton, David M. McGaughey, and Lawrence C. Brody. "Loss of the Vitamin B-12 Transport Protein Tcn2 Results in Maternally Inherited Growth and Developmental Defects in Zebrafish." Journal of Nutrition 151, no. 9 (June 16, 2021): 2522–32. http://dx.doi.org/10.1093/jn/nxab151.

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ABSTRACT Background In humans, vitamin B-12 (cobalamin) transport involves 3 paralogous proteins: transcobalamin, haptocorrin, and intrinsic factor. Zebrafish (Danio rerio) express 3 genes that encode proteins homologous to known B-12 carrier proteins: tcn2 (a transcobalamin ortholog) and 2 atypical β-domain-only homologs, tcnba and tcnbb. Objectives Given the orthologous relation between zebrafish Tcn2 and human transcobalamin, we hypothesized that zebrafish carrying null mutations of tcn2 would exhibit phenotypes consistent with vitamin B-12 deficiency. Methods First-generation and second-generation tcn2–/– zebrafish were characterized using phenotypic assessments, metabolic analyses, viability studies, and transcriptomics. Results Homozygous tcn2–/– fish produced from a heterozygous cross are viable and fertile but exhibit reduced growth, which persists into adulthood. When first-generation female tcn2–/– fish are bred, their offspring exhibit gross developmental and metabolic defects. These phenotypes are observed in all offspring from a tcn2–/– female regardless of the genotype of the male mating partner, suggesting a maternal effect, and can be rescued with vitamin B-12 supplementation. Transcriptome analyses indicate that offspring from a tcn2–/– female exhibit expression profiles distinct from those of offspring from a tcn2+/+ female, which demonstrate dysregulation of visual perception, fatty acid metabolism, and neurotransmitter signaling pathways. Conclusions Our findings suggest that the deposition of vitamin B-12 in the yolk by tcn2–/– females may be insufficient to support the early development of their offspring. These data present a compelling model to study the effects of vitamin B-12 deficiency on early development, with a particular emphasis on transgenerational effects and gene–environment interactions.

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34

McLean, G. R., M. J. Williams, C. S. Woodhouse, and H. J. Ziltener. "Transcobalamin II andin vitroProliferation of Leukemic Cells." Leukemia & Lymphoma 30, no. 1-2 (January 1998): 101–9. http://dx.doi.org/10.3109/10428199809050933.

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35

Hall, Charles A. "The neurologic aspects of transcobalamin II deficiency." British Journal of Haematology 80, no. 1 (January 1992): 117–20. http://dx.doi.org/10.1111/j.1365-2141.1992.tb06410.x.

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36

Li, N., D. S. Rosenblatt, and B. Seetharam. "Nonsense Mutations in Human Transcobalamin II Deficiency." Biochemical and Biophysical Research Communications 204, no. 3 (November 1994): 1111–18. http://dx.doi.org/10.1006/bbrc.1994.2577.

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37

Li, Weijie, and Derrick Goubeaux. "Trilineage dyspoiesis caused by transcobalamin II deficiency." Blood 129, no. 20 (May 18, 2017): 2819. http://dx.doi.org/10.1182/blood-2016-11-750364.

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38

Li, Ning, Shakuntla Seetharam, and Bellur Seetharam. "Characterization of the Human Transcobalamin II Promoter." Journal of Biological Chemistry 273, no. 26 (June 26, 1998): 16104–11. http://dx.doi.org/10.1074/jbc.273.26.16104.

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39

Li, N., S. Seetharam, D. S. Rosenblatt, and B. Seetharam. "Expression of transcobalamin II mRNA in human tissues and cultured fibroblasts from normal and transcobalamin II-deficient patients." Biochemical Journal 301, no. 2 (July 15, 1994): 585–90. http://dx.doi.org/10.1042/bj3010585.

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Transcobalamin II (TCII) is an important plasma transporter of cobalamin (Cbl; vitamin B12). In the present study, TCII gene expression in human and rat tissues and in the fibroblasts of patients with TCII deficiency was investigated. Northern-blot analyses revealed expression of TCII mRNA in many human and rat tissues. In humans, this was 14-fold higher in the kidney than in liver, whereas in the rat the levels of expression were similar in the kidney and liver. Southern-blot analysis of genomic DNA from several species revealed sequence similarity in TCII across species. Metabolic labelling and ribonuclease protection assay revealed a 43 kDa TCII protein and a fully protected TCII mRNA band in normal fibroblasts but not in fibroblasts from three TCII-deficient patients. Southern-blot analysis of genomic DNA from all these fibroblasts revealed identical restriction patterns on BamHI, HindIII, KpnI, MspI and EcoRI digestion. On the basis of these results, we suggest that TCII is expressed in multiple tissues, and its level of expression in tissues varies within the same and across species. Furthermore, the TCII deficiency characterized in this study is due to the absence of TCII protein which in turn is due to the absence or extremely low levels of its mRNA and not to detectable gross alterations in the gene structure.

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40

Hansen, Mads, and Ebba Nexø. "Isoelectric focusing of apo- and holo-transcobalamin present in human blood. Identification of a protein complexing with transcobalamin." Biochimica et Biophysica Acta (BBA) - General Subjects 992, no. 2 (August 1989): 209–14. http://dx.doi.org/10.1016/0304-4165(89)90012-3.

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41

Kurnat-Thoma, Emma L., Faith Pangilinan, Amy M. Matteini, Bob Wong, Ginette A. Pepper, Sally P. Stabler, Jack M. Guralnik, and Lawrence C. Brody. "Association of Transcobalamin II (TCN2) and Transcobalamin II-Receptor (TCblR) Genetic Variations With Cobalamin Deficiency Parameters in Elderly Women." Biological Research For Nursing 17, no. 4 (February 5, 2015): 444–54. http://dx.doi.org/10.1177/1099800415569506.

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Cobalamin (vitamin B12) deficiency is a subtle progressive clinical disorder, affecting nearly 1 in 5 individuals > 60 years old. This deficiency is produced by age-related decreases in nutrient absorption, medications that interfere with vitamin B12 absorption, and other comorbidities. Clinical heterogeneity confounds symptom detection for elderly adults, as deficiency sequelae range from mild fatigue and weakness to debilitating megaloblastic anemia and permanent neuropathic injury. A better understanding of genetic factors that contribute to cobalamin deficiency in the elderly would allow for targeted nursing care and preventive interventions. We tested for associations of common variants in genes involved in cobalamin transport and homeostasis with metabolic indicators of cobalamin deficiency (homocysteine and methylmalonic acid) as well as hematologic, neurologic, and functional performance features of cobalamin deficiency in 789 participants of the Women’s Health and Aging Studies. Although not significant when corrected for multiple testing, eight single nucleotide polymorphisms (SNPs) in two genes, transcobalamin II ( TCN2) and the transcobalamin II-receptor ( TCblR), were found to influence several clinical traits of cobalamin deficiency. The three most significant findings were the identified associations involving missense coding SNPs, namely, TCblR G220R (rs2336573) with serum cobalamin, TCN2 S348F (rs9621049) with homocysteine, and TCN2 P259R (rs1801198) with red blood cell mean corpuscular volume. These SNPs may modify the phenotype in older adults who are more likely to develop symptoms of vitamin B12 malabsorption.

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Björkstén, Karin Sparring, Lars-Håkan Thorell, and Ebba Nexø. "Circadian variation of plasma cobalamin, transcobalamin-bound cobalamin and unsaturated binding capacity of transcobalamin and haptocorrin in healthy elderly." Journal of Affective Disorders 36, no. 1-2 (December 1995): 37–42. http://dx.doi.org/10.1016/0165-0327(95)00051-8.

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43

Amagasaki, T., R. Green, and DW Jacobsen. "Expression of transcobalamin II receptors by human leukemia K562 and HL- 60 cells." Blood 76, no. 7 (October 1, 1990): 1380–86. http://dx.doi.org/10.1182/blood.v76.7.1380.1380.

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Abstract Plasma membrane receptors for the serum cobalamin-binding protein transcobalamin II (TCII) were identified on human leukemia K562 and HL- 60 cells using immunoaffinity-purified human TCII labeled with [57Co]cyanocobalamin. The Bmax values for TCII receptors on proliferating K562 and HL-60 cells were 4,500 and 2,700 per cell, respectively. Corresponding dissociation constants (kd) were 8.0 x 10(- 11) mol/L and 9.0 x 10(-11) mol/L. Rabbit TCII also bound to K562 and HL-60 cells but with slightly reduced affinities. Calcium was required for the binding of transcobalamin II to K562 cells. Brief treatment of these cells with trypsin resulted in almost total loss of surface binding activity. After removal of trypsin, surface receptors for TCII slowly reappeared, reaching pretrypsin treatment densities only after 24 hours. Reappearance of receptors was blocked by cycloheximide. TCII receptor densities on K562 and HL-60 cells correlated inversely with the concentration of cobalamin in the culture medium. This suggests that intracellular stores of cobalamin may affect the expression of transcobalamin receptors. Nonproliferating stationary-phase K562 cells had low TCII receptor densities (less than 1,200 receptors/cell). However, the density of TCII receptors increased substantially when cells were subcultured in fresh medium. Up-regulation of receptor expression coincided with increased 3H-thymidine incorporation, which preceded the resumption of cellular proliferation as measured by cell density. In the presence of cytosine arabinoside, which induces erythroid differentiation, K562 cells down-regulated expression of TCII receptors. When HL-60 cells were subcultured in fresh medium containing dimethysulfoxide to induce granulocytic differentiation, the up- regulation of TCII receptors was suppressed. This event occurred well before a diminution of 3H-thymidine incorporation and cessation of proliferation. Thus, changes in the regulation of expression of TCII receptors correlate with both the proliferative and differentiation status of cells.

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44

Amagasaki, T., R. Green, and DW Jacobsen. "Expression of transcobalamin II receptors by human leukemia K562 and HL- 60 cells." Blood 76, no. 7 (October 1, 1990): 1380–86. http://dx.doi.org/10.1182/blood.v76.7.1380.bloodjournal7671380.

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Plasma membrane receptors for the serum cobalamin-binding protein transcobalamin II (TCII) were identified on human leukemia K562 and HL- 60 cells using immunoaffinity-purified human TCII labeled with [57Co]cyanocobalamin. The Bmax values for TCII receptors on proliferating K562 and HL-60 cells were 4,500 and 2,700 per cell, respectively. Corresponding dissociation constants (kd) were 8.0 x 10(- 11) mol/L and 9.0 x 10(-11) mol/L. Rabbit TCII also bound to K562 and HL-60 cells but with slightly reduced affinities. Calcium was required for the binding of transcobalamin II to K562 cells. Brief treatment of these cells with trypsin resulted in almost total loss of surface binding activity. After removal of trypsin, surface receptors for TCII slowly reappeared, reaching pretrypsin treatment densities only after 24 hours. Reappearance of receptors was blocked by cycloheximide. TCII receptor densities on K562 and HL-60 cells correlated inversely with the concentration of cobalamin in the culture medium. This suggests that intracellular stores of cobalamin may affect the expression of transcobalamin receptors. Nonproliferating stationary-phase K562 cells had low TCII receptor densities (less than 1,200 receptors/cell). However, the density of TCII receptors increased substantially when cells were subcultured in fresh medium. Up-regulation of receptor expression coincided with increased 3H-thymidine incorporation, which preceded the resumption of cellular proliferation as measured by cell density. In the presence of cytosine arabinoside, which induces erythroid differentiation, K562 cells down-regulated expression of TCII receptors. When HL-60 cells were subcultured in fresh medium containing dimethysulfoxide to induce granulocytic differentiation, the up- regulation of TCII receptors was suppressed. This event occurred well before a diminution of 3H-thymidine incorporation and cessation of proliferation. Thus, changes in the regulation of expression of TCII receptors correlate with both the proliferative and differentiation status of cells.

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45

Magnus, Per, Erik M. Magnus, and Kåre Berg. "Transcobalamins in the etiology of neural tube defects." Clinical Genetics 39, no. 4 (June 28, 2008): 309–10. http://dx.doi.org/10.1111/j.1399-0004.1991.tb03032.x.

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46

Carmel, R., SM Neely, and RB Jr Francis. "Human umbilical vein endothelial cells secrete transcobalamin II." Blood 75, no. 1 (January 1, 1990): 251–54. http://dx.doi.org/10.1182/blood.v75.1.251.251.

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Abstract Transcobalamin II (TC II) is essential for cellular uptake of cobalamin. However, the origin of this transport protein is controversial and many organ sources have been suggested. We studied human umbilical vein endothelial cells cultured in vitro. The cells contained TC II (2.3 pmol/10(8) cells) and released progressively increasing amounts of the protein into the surrounding medium during the 3-day incubation period. This release exceeded the starting intracellular content of TC II. In contrast, endothelial cells did not contain or elaborate R binder, the other major circulating binding protein for cobalamin, Cycloheximide inhibited the elaboration of TC II, suggesting that the endothelial cells synthesize the protein. Thrombin, which stimulates tissue plasminogen activator release, did not enhance TC II release, and neither did endotoxin or mellitin. However, thrombin did appear to partially protect TC II release from inhibition by cycloheximide. Among other cells studied, human fibroblasts also released TC II into the incubation medium, while K562 human leukemia cells, ARH-77 and HS Sultan human plasma cell lines, and Raji strain lymphoblasts did not. The data suggest that endothelial cells are an important source of the metabolically crucial TC II.

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47

Carmel, R., SM Neely, and RB Jr Francis. "Human umbilical vein endothelial cells secrete transcobalamin II." Blood 75, no. 1 (January 1, 1990): 251–54. http://dx.doi.org/10.1182/blood.v75.1.251.bloodjournal751251.

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Abstract:

Transcobalamin II (TC II) is essential for cellular uptake of cobalamin. However, the origin of this transport protein is controversial and many organ sources have been suggested. We studied human umbilical vein endothelial cells cultured in vitro. The cells contained TC II (2.3 pmol/10(8) cells) and released progressively increasing amounts of the protein into the surrounding medium during the 3-day incubation period. This release exceeded the starting intracellular content of TC II. In contrast, endothelial cells did not contain or elaborate R binder, the other major circulating binding protein for cobalamin, Cycloheximide inhibited the elaboration of TC II, suggesting that the endothelial cells synthesize the protein. Thrombin, which stimulates tissue plasminogen activator release, did not enhance TC II release, and neither did endotoxin or mellitin. However, thrombin did appear to partially protect TC II release from inhibition by cycloheximide. Among other cells studied, human fibroblasts also released TC II into the incubation medium, while K562 human leukemia cells, ARH-77 and HS Sultan human plasma cell lines, and Raji strain lymphoblasts did not. The data suggest that endothelial cells are an important source of the metabolically crucial TC II.

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48

Yamada, Shoji, Leena Riittinen, Raimo Majuri, Morimichi Fukuda, and Ralph Gräsbeck. "Studies on the transcobalamin receptor in hog kidney." Kidney International 39, no. 2 (February 1991): 289–94. http://dx.doi.org/10.1038/ki.1991.35.

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49

Carmel, R. "Transcobalamin II deficiency and oral cobalamin therapy [letter]." Blood 67, no. 5 (May 1, 1986): 1522–23. http://dx.doi.org/10.1182/blood.v67.5.1522.1522.

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50

Carmel, R. "Transcobalamin II deficiency and oral cobalamin therapy [letter]." Blood 67, no. 5 (May 1, 1986): 1522–23. http://dx.doi.org/10.1182/blood.v67.5.1522.bloodjournal6751522.

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