Academic literature on the topic 'QH426 Genetics ; RG Gynecology and obstetrics'

In a rat model of intrauterine growth restriction (IUGR) induced by maternal global undernutrition, adult offspring are obese with associated metabolic disturbances. These metabolic abnormalities are all augmented by feeding a high calorie postnatal diet and reversed by neonatal leptin treatment. Evidence is now accumulating which indicates that altered epigenetic regulation and gene expression may underpin the relationship between the early life environment and metabolic disturbances in adult life. Therefore, to determine the mechanism responsible for the alterations in energy balance in the IUGR rat, this study investigated the effect of maternal diet, neonatal leptin treatment and a postnatal high fat diet on the expression and DNA methylation of genes involved in energy balance in the liver and adipose tissue of adult offspring. These genes included the peroxisome proliferator activated receptors (PPARs) and their target genes; acyl-coA oxidase (AOX), carnitine palmitoyl transferase-1 (CPT-1) and lipoprotein lipase (LPL). Real time PCR indicated that the expression of several key genes involved in energy balance, including PPARα, PPARγ and their target genes, was not altered by maternal diet or postnatal diet in the liver or adipose tissue of these offspring. However, in adipose tissue, neonatal leptin treatment resulted in an increase in the expression of most genes tested, including PPARα, PPARγ and their target genes. The increased PPARγ and LPL would facilitate the uptake of fatty acids into the adipocyte, whilst the upregulation of PPARα and its target genes AOX and CPT-1, not normally expressed in adipocytes, would direct fatty acids taken up towards the β-oxidation pathway instead of storage. This would imply that the fat cell had transformed from a fat storing cell to a fat metabolising cell. Gene expression data therefore indicated that the phenotypic changes induced by neonatal leptin treatment, i.e. the reduced weight gain, could be due to increased expression of PPARα, PPARγ and their target genes in adipose tissue: Furthermore, the effects of this are persistent, due to the specific period of leptin administration during neonatal development. There was, however, no evidence of altered DNA methylation in the promoter regions measured which could account for these persistent effects. To investigate mechanisms underlying the regulation of the PPARα promoter by leptin, the rat PPARα promoter was mapped, cloned and characterised. As part of this process, six alternatively spliced variants were identified; one from adipose tissue (P1), two from the liver (P2, P3), one from the heart (P4) and two from the kidney (P5, P6). These transcripts were found to differ in their 5’untranslated region due to tissue specific promoter usage and alternative transcription start sites. The liver and adipose specific promoters were cloned and characterised using a reporter gene strategy. They were shown to differ in their basal activity, response to known activators of transcription and to neonatal leptin treatment. The regulation of the PPARα promoter by leptin was investigated and shown to function via a non-canonical mechanism requiring both signal transducer and activators of transcription (Stat3) and specificity protein-1 (Sp1), which act at a unique region of the liver specific P2 promoter. The adipose specific P1 promoter was shown to be unresponsive to leptin treatment. Furthermore, real time PCR with primers specific to the P1 and P2 PPARα transcripts indicated that the increased PPARα expression seen in leptin treated offspring was due to an increase in the P2 specific transcript, not the P1 transcript. This indicated that the neonatal leptin treatment facilitated a selective switch in promoter usage to increase the expression of PPARα and its target genes in a tissue in which they are not normally expressed, thus inducing an altered metabolism within the adipocytes of these offspring.

All eukaryotic cells possess mitochondrial DNA (mtDNA), which is maternally inherited through the oocyte, its replication being regulated by nuclear-encoded replication factors. It was hypothesised that mtDNA replication is highly regulated in oocytes, pre-implantation embryos and embryonic stem cells (ESCs) and that this may be disrupted following nuclear transfer (NT). MtDNA copy number decreased between 2-cell and 8-cell staged porcine embryos and increased between the morula and expanded blastocyst stages, coinciding with increased expression of mtDNA replication factors. Competent porcine oocytes replicated their mtDNA prior to and during in vitro maturation to produce and maintain the 100000 mtDNA copies required for fertilisation. Those oocytes in which mtDNA replication was delayed had reduced developmental ability. Expression of pluripotency-associated genes decreased as murine ESCs differentiated into embryoid bodies, although expression of mtDNA replication factors did not increase until the stage equivalent to organogenesis. Cross-species NT embryos in which the donor cell-derived mtDNA was replicated produced decreased developmental outcomes compared to those in which no mtDNA replication took place. Disruption of the strict regulation of mtDNA replication that occurs during early embryogenesis, as is likely following NT, may therefore contribute to the reduced developmental ability of embryos produced using such techniques.

Tolerance of the semi-allogeneic fetus presents a significant challenge to the maternal immune system. The effect of pregnancy on maternal cellular immunity was established by assessing maternal effector and regulatory T-cell subsets during human pregnancy. This demonstrated that an increase in maternal peripheral regulatory T-cells or a shift from a Th1 to Th2 phenotype was not a requirement for normal pregnancy. We also determined the profound impact of maternal Cytomegalovirus seropositivity on maternal T- cell dynamics. T-cells with specificity for fetal epitopes have been detected in women with a history of pregnancy but it has been thought that such fetal specific cells were deleted during pregnancy. We identified, using MHC-peptide multimers, fetal-specific CD8 T-cells in half of all pregnancies. The fetal-specific response increased during pregnancy and persisted in the post natal period. Fetal-specific cells demonstrated an effector memory phenotype and retained functional potential. These data show that the development of a fetal-specific adaptive cellular immune response is a normal consequence of human pregnancy. Women with recurrent miscarriage were found to have abnormal T-cell function, with increased IFN\(\gamma\) and Il-17 production. Fetal specific T-cells were also detected in this cohort and progesterone attenuated their function, which may have therapeutic implications.

I investigated the role of genetic, environmental and intrauterine factors in child development using data from two large twin studies; the East Flanders Prospective Twin Survey (EFPTS) and the Twins and Multiple Births Association Heritability Study (TAMBAHS). An association between birth weight and child development has already been established. Potential associations between other factors of the intrauterine environment and child development were investigated in this thesis. Heritabilities of the umbilical cord, IQ, temperament and behaviour problems were estimated. Fetal characteristics, such as birth weight, placental weight and morphology, umbilical cord knots, length and insertions were investigated in relation to cognitive development in the EFPTS study. The impact of maternal pre-pregnancy weight on temperament and behaviour problems was examined in the TAMBAHS study. High heritability estimates were observed for certain dimensions of the umbilical cord, temperament and IQ; for behaviour problems, genetic, shared and non-shared environment were important. Low birth weight and cord knotting was associated with lower IQ; an association was observed between maternal overweight and children aggressive behaviour. The results are discussed in the context of the Developmental Origins of Health and Disease (DOHaD) hypothesis, highlighting the role of the intrauterine environment in child development.

The multiple pterygium syndromes are a heterogeneous group of conditions in which arthrogryposis (joint contractures), pterygia (webbing) and a variety of other developmental anomalies are present. It is caused by lack of fetal movement in the womb. Mutations in CHRNG, the embryonic subunit of the acetylcholine receptor (AChR), cause some of the cases. CHRNG mutation analysis was undertaken in a large patient cohort of 100 families and the mutations identified were included in a new Locus Specific Database. Genotype phenotype analysis showed that pterygia were almost invariably present in the CHRNG mutation positive patients. It was hypothesised that mutations in other genes necessary for fetal AChR function may cause fetal akinesia. Using a candidate gene approach a homozygous frameshift mutation in RAPSN was identified in one family and a homozygous splice site DOK7 mutation in second family. Mild mutations in both RAPSN and DOK7 have been previously identified in the congenital myasthenic syndromes (CMS). Thus, mild mutations in RAPSN and DOK7 cause CMS whereas severe mutations cause fetal akinesia. Finally, work was done to identify a novel cause of fetal akinesia in a consanguineous family using an autozygosity mapping approach. A region of homozygosity was located and candidate genes sequenced.