Academic literature on the topic 'B-Chromosom'

Die Therapie mit dem bispezifischen Antikörper-Konstrukt Blinatumumab wurde in der TOWER-Studie bei rezidivierten und refraktären Patienten mit Philadelphia-Chromosom-negativer (Ph-) B-Vorläufer-ALL (Akute Lymphatische Leukämie) erfolgreich geprüft. Eine neue Auswertung der Studie zeigt jetzt, dass die Erhaltungstherapie mit Blimatumumab nach Erreichen einer kompletten hämatologischen Remission (CHR) für nicht stammzelltransplantierte Patienten aufgrund der Verlängerung des Gesamtüberlebens (OS) vorteilhaft ist.

Die Tiefe des Ansprechens, definiert durch die minimale Resterkrankung (MRD), erreicht innerhalb der hämatologischen malignen Erkrankungen einen immer höheren Stellenwert und wurde vielfach beim vergangenen ASH diskutiert. Sie ist auch ein Prädiktor für die Prognose von Patienten mit Philadelphia- Chromosom-positiver (Ph +) akuter lymphatischer Leukämie (ALL), wie in Orlando Ende 2019 gezeigt wurde. Eine Vertiefung der MRD wurde bei pädiatrischen B-ALL-Patienten mit dem neuen Standard Blinatumomab erreicht.

ZusammenfassungIn einer Übersicht werden einige molekulargenetische Aspekte der Gerinnungsfaktoren VII, VIII, IX und X dargestellt. Das Spektrum der Mutationen wird charakterisiert, das zu den genetisch bedingten Defekten Hämophilie A und B, Faktor-VII- und -X-Mangel führt. Für die Hämophilien A und B wird der genetische Beratung auf der Grundlage des X-chromosomalen Erbganges und der indirekten und direkten genomischen Analyse an ausgewählten Beispielen vorgestellt.Die Gene der Vitamin-K-abhängigen Serinproteasen Faktor VII und Faktor X sind auf dem Chromosom 13 lokalisiert. Mutationen führen zu autosomal-rezessiv vererbtem Faktor-VII- oder Faktor-X-Mangel. Das Mutationspektrum, die Rolle von Polymorphismen der Gene und das Spektrum der spontanen Blutungen dieser seltenen Blutungsleiden werden charakterisiert und Genotyp-Phänotyp-Korrelationen aufgezeigt.

The Queensland fruit fly, Bactrocera tryoni, like the Mediterranean fruit fly, Ceratitis capitata, has a diploid complement of 12 chromosomes, including five pairs of autosomes and a XX/XY sex chromosome pair. Characteristic features of each chromosome are described. Chromosomal homology between B. tryoni and C. capitata has been determined by comparing chromosome banding pattern and in situ hybridisation of cloned genes to polytene chromosomes. Although the evidence indicates that a number of chromosomal inversions have occurred since the separation of the two species, synteny of the chromosomes appears to have been maintained.Key words: tephritid fruit fly, Bactrocera tryoni, polytene chromosomes, in situ hybridisation, chromosomal homology.

Sex determination in frogs (anurans) is genetic and includes both male and female heterogamety. However, the origins of the sex chromosomes and their differentiation processes are poorly known. To investigate diversity in the origins of anuran sex chromosomes, we compared the chromosomal locations of sex-linked genes in 4 species: the African clawed frog (Xenopus laevis), the Western clawed frog (Silurana/X. tropicalis), the Japanese bell-ring frog (Buergeria buergeri), and the Japanese wrinkled frog (Rana rugosa). Comparative mapping data revealed that the sex chromosomes of X. laevis, X. tropicalis and R. rugosa are different chromosome pairs; however, the sex chromosomes of X. tropicalis and B. buergeri are homologous, although this may represent distinct evolutionary origins. We also examined the status of sex chromosomal differentiation in B. buergeri, which possesses heteromorphic ZW sex chromosomes, using comparative genomic hybridization and chromosome painting with DNA probes from the microdissected W chromosome. At least 3 rearrangement events have occurred in the proto-W chromosome: deletion of the nucleolus organizer region and a paracentric inversion followed by amplification of non-W-specific repetitive sequences.

Chromosomal data and karyological relationships provide valuable information about karyotype evolution and speciation. For the genus Bunium, the chromosomal data are limited. In the present study, the chromosomal data of 10 taxa are provided, 6 of which are given for the first time, 2 present new chromosome numbers, and 2 agree with previous reports. Four different chromosome numbers (2n=18, 20, 22 and 40) were detected, and 2n=40 is a new number in the genus Bunium. B. brachyactis is the first polyploid species of the genus with a ploidy level of 4x. The most asymmetric karyotypes are those of B. pinnatifolium and B. sayae. Regarding karyological relationships, B. pinnatifolium forms a monophyletic group by quite different karyological features such as large chromosomes, more submedian chromosomes and the most asymmetric karyotypes. In addition, the other 5 taxa form a strong monophyletic group. B. verruculosum and B. ferulaceum are cytotaxonomically very close species, as are B. sayae and B. elegans var. elegans. The chromosome numbers of 2 Turkish species, B. nudum and B. sivasicum, remain unknown. The presented results provide important contributions to the cytotaxonomy of Bunium.

Supernumerary (B) chromosomes are dispensable genomic elements occurring frequently among grasshoppers. Most B chromosomes are enriched with repetitive DNAs, including satellite DNAs (satDNAs) that could be implicated in their evolution. Although studied in some species, the specific ancestry of B chromosomes is difficult to ascertain and it was determined in only a few examples. Here we used bioinformatics and cytogenetics to characterize the composition and putative ancestry of B chromosomes in three grasshopper species, Rhammatocerus brasiliensis, Schistocerca rubiginosa, and Xyleus discoideus angulatus. Using the RepeatExplorer pipeline we searched for the most abundant satDNAs in Illumina sequenced reads, and then we generated probes used in fluorescent in situ hybridization (FISH) to determine chromosomal position. We used this information to infer ancestry and the events that likely occurred at the origin of B chromosomes. We found twelve, nine, and eighteen satDNA families in the genomes of R. brasiliensis, S. rubiginosa, and X. d. angulatus, respectively. Some satDNAs revealed clustered organization on A and B chromosomes varying in number of sites and position along chromosomes. We did not find specific satDNA occurring in the B chromosome. The satDNAs shared among A and B chromosomes support the idea of putative intraspecific ancestry from small autosomes in the three species, i.e., pair S11 in R. brasiliensis, pair S9 in S. rubiginosa, and pair S10 in X. d. angulatus. The possibility of involvement of other chromosomal pairs in B chromosome origin is also hypothesized. Finally, we discussed particular aspects in composition, origin, and evolution of the B chromosome for each species.

B chromosomes are extra chromosomes from the normal chromosomal set, found in different organisms, highlighting their presence on the group of fishes. Callichthys callichthys from the upper Paraná River has a diploid number of 56 chromosomes (26 m-sm + 30 st-a) for both sexes, with the presence of a sporadically acrocentric B chromosome. Moreover, one individual presented a diploid number of 57 chromosomes, with the presence of a morphologically ill-defined acrocentric B chromosome in all analyzed cells. The physical mapping of 5S and 18S rDNA shows multiple 5S rDNA sites and only one pair of chromosomes with 18S sites in C. callichthys, except for two individuals. These two individuals presented a third chromosome bearing NORs (Ag-staining and 18S rDNA) where 5S and 18S rDNA genes are syntenic, differing only in position. The dispersion of the 18S rDNA genes from the main st-achromosome pair 25 to one of the chromosomes from the m-sm pair 4 would have originated two variant individuals, one of which with the ill-defined acrocentric B chromosome. Mechanisms to justify the suggested hypothesis about this B chromosome origin are discussed in the present study.

The occurrence of repetitive DNA in autosomes and B chromosomes of Bergiaria westermanni was examined using conventional and molecular cytogenetic techniques. This species exhibited 2n = 56 chromosomes, with intra- and interindividual variation in the number of heterochromatic B chromosomes (from 0 to 4). The 5S rDNA was localized in pairs 1 and 5, and histone probes (H1, H3, and H4) and U2 small nuclear RNA were syntenic with 5S rDNA in pair 5. Histone sequences were also located in chromosome pair 14. The (GATA)n sequence was dispersed throughout the autosomes and B chromosomes, with clusters (microsatellite accumulation) in some chromosome regions. The telomeric probe revealed no signs of chromosomal rearrangements in the genome of B. westermanni. The 45S rDNA sites were detected in the terminal region of pair 27; these sites corresponded to a GC-rich heterochromatin block. In addition, 3 of the 4 B chromosomes also contained 45S rDNA copies. Silver nitrate staining in interphase nuclei provided indirect evidence of the expression of these rRNA genes in B chromosomes, indicating the probable origin of these elements. This report shows plasticity in the chromosomal localization of repeat DNA in B. westermanni and features a discussion of genomic diversification.

Whole-chromosome painting probes were developed for each of the 10 chromosomes of maize by producing amplifiable libraries of unique sequences of oligonucleotides that can generate labeled probes through transcription reactions. These paints allow identification of individual homologous chromosomes for many applications as demonstrated in somatic root tip metaphase cells, in the pachytene stage of meiosis, and in interphase nuclei. Several chromosomal aberrations were examined as proof of concept for study of various rearrangements using probes that cover the entire chromosome and that label diverse varieties. The relationship of the supernumerary B chromosome and the normal chromosomes was examined with the finding that there is no detectable homology between any of the normal A chromosomes and the B chromosome. Combined with other chromosome-labeling techniques, a complete set of whole-chromosome oligonucleotide paints lays the foundation for future studies of the structure, organization, and evolution of genomes.

Orientador: Cesar Martins
Abstract: One of the biggest challenges in chromosome biology is to understand the occurrence and complex genetics of extra, non-essential karyotype elements, commonly known as supernumerary B chromosomes (Bs). Bs are present in diverse species of eukaryotes and their molecular characterization remains elusive for years. A distinguished feature that makes them different from the normal chromosomes (called A chromosomes) is their way of inheritance in irregular fashion. Over the last decades, their genetic composition, function and evolution have remained an unresolved query, although a few successful attempts have been made to address these phenomena. The non-Mendelian inheritance and unpairing/non-recombining abilities make the B chromosomes immensely interesting for genomics studies, thus arising different questions about their genetic composition, survival, maintenance and role inside the cell. This study aims to uncover these phenomena in different species. Here, we sequenced the genomes of three model organisms including fish species Astyanax mexicanus and Astyanax correntinus, and grasshopper Abracris flavolineata with (B+) and without Bs (B-) to identify the B-localized sequences, called B chromosome blocks (“B-blocks”). We established approaches for this analysis that comprised of steps such as comparative genomics analysis and annotation of B chromosomal genes and DNA repeat types. The next generation sequencing (NGS) analyses identified thousands of genes fragments as well as... (Complete abstract click electronic access below)
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Nos últimos anos, alguns estudos de mapeamento cromossômico foram realizados em gafanhotos do grupo Acridomorpha, preferencialmente através do uso de sondas de sequências repetitivas. Este trabalho tem como objetivo contribuir para uma melhor compreensão dos aspectos cromossômicos evolutivos em gafanhotos acridomorfos e da diversidade genética de Ommexecha virens. Os genes de cópia única Hsp83, Hsp70, Hsp27, Ubi, Lys foram localizados nos cromossomos meióticos de Ommexecha virens, Xyleus discoideus angulatus, Tropidacris collaris e Stiphra robusta e Lys em Schistocerca pallens através de Hibridização in situ permanente (PISH). Sequências repetitivas de rDNA 45S, rDNA 5S e Histona H3 foram localizadas em O virens através de Hibridização in situ fluorescente (FISH). Em O. virens também foi analisado o cromossomo B por técnicas convencionais, diferenciais e moleculares, bem como a estrutura genética de oito populações naturais (seis de Pernambuco, uma da Bahia e uma do Ceará) do Nordeste brasileiro com o marcador ISSR (regiões entre sequências de repetições simples). Os genes de cópia única apresentaram um padrão conservado de localização em pares cromossômicos grandes, preferencialmente o L1, exceto para Hsp70 e Ubi, localizados no L2. Sinais secundários foram observados em cromossomos médios. A conservação apresentada deve-se a ausência ou pequena ocorrência de rearranjos nos cromossomos destes cariótipos, o que reduz o risco de eventos deletérios, bem como pela localização coincidente com regiões ricas em heterocromatina constitutiva. A conservação da localização destes genes indicou os cromossomos portadores dos locus gênicos ancestrais para os genes mapeados. O estudo do cromossomo B em O. virens revelou similaridade de tamanho e marcação CMA3 positiva com o cromossomo 9, sugerindo a possível origem deste cromossomo. Contudo, a presença de sítios de rDNA 45S e Histona H3 no cromossomo 9 e ausência no B, provavelmente pela deleção dessas sequências neste cromossomo, não permitem descartar a possibilidade do B ter se originado de outro cromossomo. A análise genética populacional em O. virens mostrou três cluster, os quais exibiram relação com aspectos da biologia da espécie, a paisagem dos ambientes amostrados e com as modificações geológicas ocorridas no Nordeste brasileiro, em particular a formação do complexo da Borborema e a Chapada do Araripe.
In recent years, some chromosomal mapping studies were performed in Acridomorpha group grasshoppers, preferably through the use of repetitive sequence probes. In this work in order to contribute to a better understanding of evolutionary chromosomal aspects of acridomorphs and genetic diversity of Ommexecha virens. The single copy genes Hsp83, Hsp70, Hsp27, Ubi, Lys were located in meiotic chromosomes of Ommexecha virens, Xyleus discoideus angulatus, Tropidacris collaris and Stiphra robusta, and Lys in Schistocerca pallens through permanent situ hybridization (PISH). Repetitive sequences of 45S rDNA, 5S rDNA and H3 histone were located in the O. virens via fluorescent in situ hybridization (FISH). In O. virens was also analyzed the B chromosome by conventional, differential and molecular techniques and genetic structure of eight natural populations (six of Pernambuco, one of Bahia and one of Ceará) of the Northeast of Brazil with ISSR marker (inter simple sequence repeat). Single copy genes showed a conserved pattern of location in large chromosomal pairs, preferably L1, except for Hsp70 and Ubi, located in L2. Secondary signals were observed on medium chromosomes. The presented conservation due to absence or occurrence of small rearrangements in these karyotypes, which reduces the risk of deleterious events as well as for matching location with regions rich in heterochromatin. The conservation of the location of these genes indicated the chromosomes carrying the genic locus ancestors to the mapped genes. The study of B chromosome of O. virens revealed similarity in size and CMA3 positive marking to chromosome 9, suggesting the possible origin of this chromosome. However, the presence of 45S rDNA sites and H3 histone on chromosome 9 and the absence on B, probably due to deletion of these sequences in this chromosome, do not allow to rule out the possibility of B have originated from another chromosome. Population genetic analysis O. virens showed three clusters, which exhibited relationship with aspects of the biology of the species, the landscape of the study sites and the geological changes occurred in northeastern of Brazil, in particular the formation of the Borborema and Araripe plateaus.

Estudos de citogenética comparativa são rotineiramente desenvolvidos a partir da comparação dos padrões de bandamentos cromossômicos. Contudo, quando se trata de espécies que apresentam genomas altamente rearranjados, como no caso das espécies de Akodon, ou que são muito divergentes, a comparação de cromossomos por padrões de bandas torna-se inadequada. Como consequência, a pintura cromossômica tem se tornado o método de escolha assertivo, já que permite comparação genômica no nível citogenético. Nessa tecnologia sondas de um cromossomo inteiro de uma determinada espécie são hibridadas in situ em cromossomos de outra espécie, detectando as regiões homólogas entre os genomas. No presente estudo comparamos os cariótipos altamente diferenciados de algumas espécies de Akodon por meio de pintura cromossômica recíproca com uso de sondas espécie-específicas, obtidas a partir de cromossomos separados por citometria de fluxo. Os resultados revelaram homologia completa entre os complementos de Akodon sp. n. (ASP), 2n=10, A. cursor (ACU), 2n=15, A. montensis (AMO), 2n=24 e A. paranaensis (APA), 2n=44 e evidenciaram com precisão muitos rearranjos cromossômicos entre os complementos das espécies. Rearranjos Robertsonianos e em tandem, inversões pericêntricas e/ou reposicionamento de centrômero, inversão paracêntrica, translocações, inserções e existência de sítios frágeis nos complementos foram observados. A pintura cromossômica empregando o conjunto de sondas de APA para 21 autossomos mais cromossomos X e Y evidenciou oito segmentos sintênicos compartilhados entre A. montensis, A. cursor e Akodon sp. n., cinco associações exclusivas para A. cursor e seis para Akodon sp. n. Foi também detectada homologia completa dos cromossomos X, com exceção da região heterocromática de ASP X, e até mesmo dos cromossomos Y que geralmente não apresenta sinal hibridação entre diferentes espécies de mamíferos. Esses dados indicam que essas espécies intimamente relacionadas passaram por um processo recente de intensa diferenciação autossômica, no qual se conservou a homologia total, por exceção de Akodon sp. n., entre os cromossomos sexuais. Pertencente a tribo Akodontini, Deltamys Thomas 1917 é um táxon pouco estudado e que é raramente capturado. Utilizando-se de caracteres morfológicos ou genéticos, alguns autores consideram Deltamys como um gênero pleno enquanto outros acreditaram que esse devesse ser referido como subgênero ou sinônimo de Akodon. A única espécie formalmente descrita é Deltamys kempi que apresenta cariótipo básico com 2n=37 nos machos e 2n=38 nas fêmeas, NF=38, com sistema de determinação de sexo do tipo X1X1X2X2: X1X2Y. Uma característica citogenética que distingue Deltamys de Akodon é a presença de um pequeno par metacêntrico marcador em Akodon. Um cariótipo com 2n=40 e NF=40; XX: XY foi relacionado ao gênero Akodon porém, como em Deltamys kempi , esse complemento não apresenta o pequeno par metacêntrico. As análises filogenéticas de máxima parcimônia e máxima verossimilhança baseadas em sequências do gene mitocondrial do citocromo b evidenciaram o monofiletismo dos espécimens de Akodon sp. 2n=40, e o monofiletismo de Deltamys kempi. Além disso, revelaram que Akodon sp. é grupo irmão de Deltamys kempi, estando mais relacionado a este último gênero do que às demais espécies de Akodon, sugerindo a inclusão dos espécimens portadores do cariótipo com 2n=40 em Deltamys. Dessa forma, o gênero Deltamys se mostrou mais diverso do que até então se tinha conhecimento, agrupando duas linhagens: Deltamys kempi , 2n=37-38 ; X1X1X2X2: X1X2Y e Deltamys sp. 2n=40, XX: XY, que apresentam entre sí uma marcante divergência genética que chega a 12, 1%. Um cariótipo com 2n=50, NF=48 foi descrito para espécimes de Thaptomys Thomas,1916, coletados em Una, estado da Bahia, Brasil, que são indistinguíveis morfologicamente dos Thaptomys nigrita que apresentam 2n=52, NF=52, encontrados em outras localidades brasileiras. Foi então proposto que esse novo cariótipo com 2n=50 pertencesse a uma espécie críptica de Thaptomys nigrita, uma vez que os rearranjos cromossômicos observados somados a distância geográfica pode representar uma barreira reprodutiva entre as duas formas. Com o intuito de se estabelecer as relações entre indivíduos de Thaptomys com os dois números diplóides, análises filogenéticas moleculares foram realizadas com o uso de dezoito sequências do gene mitocondrial do citocromo b provenientes de espécimes cariotipados coletados ao longo da distribuição geográfica do gênero. Dois clados principais, Nordeste (A) que agrupa espécimens com 2n=50 e Sudeste (B) que agrupa espécimes com 2n=52, foram recuperados por análises de máxima parcimônia e máxima verossimilhança. As relações filogenéticas intra-genéricas corroboram os distintos números diplóides, e mostram os cariótipos com 2n=50 e 2n=52 como clados irmãos entre si separados pela cladogênese basal de Thaptomys . No presente trabalho são apresentados estudos de filogenia molecular e citogenética para o gênero monotípico de roedor fossorial Blarinomys Thomas 1896. Foram realizadas análises de máxima parcimônia e máxima verossimilhança com base em sequências do gene mitocondrial citocromo b , para amostra de 11 exemplares de B. breviceps provenientes de nove localidades de quatro estados do território brasileiro. Todas as topologias recuperaram duas linhagens principais: um clado Nordeste (A) e outro Sudeste. O clado sudeste agrupou dois clados irmãos, B e C. A divergência de sequência entre os indivíduos variou de: 4,7- 8,0% entre os clados nordeste e sudeste; 4,3-5,7% entre os clados B e C; 6,1-8,0% entre os clados nordeste; e B, e 4,7-6,4% entres os clados nordeste e C. Dentro dos clados a divergência variou de 0- 4,2% no clado nordeste, foi de 0,7% no clado B, e variou de 0,1- 1,3% no clado C. Variação entre espécimes da mesma região geográfica foi de 0-1,3%. Os estudos de citogenética de cinco exemplares revelaram alta diversidade cariotípica com cinco números diplóides distintos: 2n=52 (48A+2Bs, XY), 2n=43 (37A+4Bs, XX), 2n=37 (34A+1B, XY), 2n=34 (32A, XX) e 2n=31 (27A+2Bs, XX) e mesmo número de braços autossômicos (NF=50), excluindo-se os cromossomos sexuais e os supernumerários. Foram observados polimorfismos decorrentes de rearranjos Robertsonianos, além de variação de 0 a 4 cromossomos Bs, que são heterogêneos quanto a morfologia, constituição de heterocromatina e presença de sinais teloméricos intersticiais (ITS). ITS também foram observados na região pericentromérica de alguns pares autossômicos com dois braços em três dos exemplares. Foi realizada pintura cromossômica com sonda do cromossomo X de Akodon cursor (ACU X). Nossos dados revelaram uma diversidade até então desconhecida para Blarinomys , mostrando duas linhagens distintas correspondentes a regiões na Mata Atlântica e um extraordinário polimorfismo cromossômico.
Traditionally comparative cytogenetic studies are based mainly on banding patterns. Nevertheless, when dealing with species with highly rearranged genomes, as in Akodon species, or with other highly divergent species, cytogenetic comparisons of banding patterns prove to be inadequate. Hence, comparative chromosome painting has become the method of choice for genome comparisons at the cytogenetic level, since it allows complete chromosome probes of a species to be hybridized in situ onto chromosomes of other species, detecting homologous genomic regions between them. In the present study, we have explored the highly rearranged complements of the Akodon species using reciprocal chromosome painting through species-specific chromosome probes obtained by chromosome sorting. The results revealed complete homology among the complements of Akodon sp. n. (ASP), 2n=10, A. cursor (ACU), 2n=15, A. montensis (AMO), 2n=24 and A. paranaensis (APA), 2n=44 and extensive chromosome rearrangements have been detected within the species with high precision. Robertsonian and tandem rearrangements, pericentric inversions and/or centromere repositioning, paracentric inversion, translocations, insertions and fragile sites were observed. The chromosome painting using the APA set of 21 autosomes plus X and Y exhibited eight syntenic segments that are shared with A. montensis, A. cursor and Akodon sp. n. plus five exclusive associations for A. cursor and six for Akodon sp. n. Chromosomes X, except for the heterochromatin region of ASP X, and even chromosome Y that often present no hybridization signal when hybridized between species of mammals, shared complete homology among the species. These data indicate that all those closely related species have experienced a recent intensive process of autosomic differentiation, in wich, there is still complete maintenance, except for chromosome X of Akodon sp. n., of the sex chromosomes homologies. Member of the tribe Akodontini, Deltamys Thomas 1917 is a poorly studied and rarely collected taxon. Based on morphological or genetic characters, some authors considered Deltamys as a full genus while others regarded it as subgenus or synonym of Akodon. The single described species, Deltamys kempi presents a basic karyotype with 2n=37 in males and 2n=38 in females, FN=38, and with sex determination system of the type X1X1X2X2: X1X2Y. A cytogenetic character that distinguishes Deltamys from Akodon is the presence of a small metacentric pair marker in Akodon. A karyotype with 2n=40 and FN=40; XX: XY was related to the genus Akodon, but as in Deltamys kempi, this complement does not present the small metacentric pair. Phylogenetic analyses of maximum parsimony and maximum likelihood based on sequences of the mitochondrial gene cytochrome b evidenced the monophyly of a clade grouping specimens of Akodon sp. 2n=40 and monophyly of a clade containing specimens of Deltamys kempi. Besides that, the analyses showed that Akodon sp. is the sistergroup of Deltamys kempi, thus more related to this genus than to other species of Akodon and suggesting the placement of specimens with 2n=40 Deltamys. The genus Deltamys is, thus, more diverse than previously thought, grouping two lineages: Deltamys kempi, 2n=37-38 ; X1X1X2X2: X1X2Y and Deltamys sp. 2n=40, XX: XY, with a marked genetic divergence of 12,1% between them. A karyotype with 2n=50, FN=48 has been described for specimens of Thaptomys Thomas, 1916 collected at Una, State of Bahia, Brazil, which are morphologically indistinguishable from Thaptomys nigrita with 2n=52, FN=52 found in other Brazilian localities. It has been hence proposed that this new karyotype with 2n=50 could belong to a distinct species, cryptic of Thaptomys nigrita, once chromosome rearrangements observed along with the geographic distance could represent a reproductive barrier between both forms. Molecular phylogenetic analyses using the cytochrome b sequences of eighteen karyotyped specimens of Thaptomys were performed attempting to establish the relationships among the individuals along the geographic distribution of the genus. Two major clades, Northeastern (A) with specimens with 2n=50 and Southeastern (B) with specimens with 2n=52, were reconstructed by maximum parsimony (MP) and maximum likelihood (ML). The intra-generic relationships recovered by phylogenetic analyses corroborated the distinct diploid numbers. The 2n=50 and 2n=52 karyotypes appeared as monophyletic separated by the basal cladogenesis of the genus, sister-group to each other. We present molecular phylogenetic and cytogenetic data on the monotypic fossorial rodent genus Blarinomys . Maximum parsimony and maximum likelihood based on cytochrome b gene sequences were performed for a sample of 11 individuals from nine localities of four states of Eastern Brazil. All topologies recovered two main lineages: a Northeastern (A) and a Southeastern clade. The Southeastern grouped two sister-clades B and C. Sequence divergence between individuals ranged from 4.7-8.0% between northeastern and southeastern clades, from 4.3-5.7% between clades B and C, from 6.1-8.0% between clades northeastern and B, and from 4.7-6.4% between clades northeastern and C. Within the clades, divergence varied from 0- 4.2% in the northeastern clade, was 0.7% in the clade B, and varied from 0.1- 1.3% in clade C. Variation among specimens from the same geographic regions ranged from 0-1.3%. Cytogenetic studies of five individuals revealed high karyotypic diversity with five distinct diploid numbers: 2n=52 (48A+2Bs,XY) from state of Bahia, and 2n=43 (37A+4Bs,XX), 2n=37 (34A+1B,XY), 2n=34 (32A,XX), and 2n=31 (27A+2Bs,XX) from state of São Paulo; and same number of autosomic arms (FN=50) excluding sex chromosomes and supernumeraries. Polymorphisms are due to Robertsonian rearrangements, in addition to the variation from none to four B chromosomes, which are heterogeneous regarding morphology, heterochromatin constitution and presence of interstitial telomeric signals (ITS). ITSs were also observed in the pericentromeric regions of some biarmed autosomic pairs of three specimens. Our results revealed a high unknown diversity for Blarinomys , showing two distinct lineages corresponding to regions of the Atlantic Rainforest, besides an extraordinary chromosomal polymorphism.

Thesis (Ph. D.)--Illinois State University, 1998.
Title from title page screen, viewed July 5, 2006. Dissertation Committee: David F. Weber (chair), Marjorie A. Jones, Anthony Otsuka, Derek McCracken, Radheshyam Jayaswal. Includes bibliographical references (leaves 85-91) and abstract. Also available in print.

We have examined DNA samples from 25 hemophilia B patients (21 B- patients, 2 BR patients and 2 B+ patients) and 51 normal subjects with molecular probes (pHFIX and 2 genomic fragments). By structural gene analysis, 4 out of 7 patients who developed anti-factor IX antibodies were detected to have gross factor IX gene deletion. Although these four patients showed normal pattern of HPRT gene detected by pCDHPRT, the gene deletions were found to expand more than 34kb including with entire factor IX exons. Quantitative Southern blot analysis of factor IX gene of the patient's family members indicated that the gene deletion was inherited in one family, establishing the carrier status of 2 aunts, 2 cousins and one sister. The 'de novo' mutation of factor IX gene was also established in 2 families. Three patients with anti-factor IX antibodies and 17 patients without antibody to factor IX had normal pattern of factor IX gene by several restriction enzyme digestions. Analysis of factor IX gene of three patients with anti-factor IX antibodies and two B+ patients are now underway to detect the unique gene defects which may be responsible for the disease Phenotypes. Common RFLPs in factor IX gene were studied in normal Japanese subjects. More than 80 X chromosomes were analysed with BamHI, Ddel, MspI, TaqI or XmnI digestion, followed by hybridization with pHFIX. RFLPs produced by these enzymes were found to be uncommon or possibly absent in normal Japanese subjects. These results imply that racial differences in the frequency of gene polymorphisms should be seriously considered before initiating the gene counseling by the genetic probes.

About 250 individuals belonging to 44 families with hemophilia A or B were studied in our laboratory. The detection of carriers was first established by pedigree analysis of each family . and coagulation and immunological assays of factor VIII or IX. The availability of specific probes for the molecular study of these two genes makes possible a diagnosis with certainty in the case of informative families. 25 families of hemophilia A were studied. For each person, blood was collected into EDTA and leucocyte DNA was extracted, digested by restriction endonucleases, electrophoresed in 0.9 % agarose gels and transferred to nitrocellulose filters by Southern blotting. Two probes were used for the analysis of factor VIII gene. The St 14 probe (J.L. Mandel) located on the q28 region of the X chromosome and closely linked to the gene, determines a restriction fragment length polymorphism (RFLP) when the DNA is digested by the enzyme TaqI. The p114-12 genomic probe (Genentech) corresponding to the exons 17 and 18 of the factor VIII gene, reveals a RFLP in the DNA digested by the enzyme BclI. 19 families -of hemophilia B were studied. A total factor IX cDNA probe was used for the screening of potential deletions in the case of hemophiliacs with circulating antibodies. A genomic probe containing the exons II, III and IV of factor IX was used to detect the TaqI RFLP. For the study of factor VIII gene, the extragenic probe St 14 gives a very high percentage of informativity (about 90 %) but recombination can occur between the probe and the gene. The p 114-12 probe, which is used to confirm the results given by the St 14 probe, gives about 20 % informativity. In our study, we were able to diagnose carrier state with certainty in 92 % of the families. For hemophilia B, the genomic probe gives about 40 % informativity. A large deletion of the region of the factor IX gene has been found in one family and remains to be mapped. In conclusion, carrier detection and prenatal diagnosis can be established with certainty by molecular studies in most cases of hemophilia A using the St 14 probe, with a 5 % risk of recombination when the BclI RFLP cannot confirm. This diagnosis is possible in about 40 % of the cases of hemophilia B.