published_or_final_version / Medicine / Master / Master of Philosophy

published_or_final_version / Medicine / Doctoral / Doctor of Philosophy

published_or_final_version / Botany / Doctoral / Doctor of Philosophy

Cystinuria is an autosomal recessive disorder of the kidneys and intestine with defective luminal transport of cystine and other dibasic amino acids (ornithine, arginine, and lysine). Three phenotypes have been described, based on urinary excretion of these amino acids in obligate heterozygotes: Type I (silent carriers); Type II (moderate elevation); and Type III (mild elevation). The SLC3AI (D2H) protein has been shown to enhance cystine reabsorption and mutations in D2H have been reported in cystinuria. The aims of this study were to characterize D2H gene structure and to identify mutations in Quebec patients. / The D2H cDNA was used to isolate five genomic clones and to characterize the entire gene. The gene spans over 40 kb and contains 10 exons. SSCP and Southern blotting techniques were successful in identifying six novel mutations (2 large deletions, 3 missense mutations, and one 2bp deletion) in twenty cystinuric patients (8 Type I/I, 9 Type I/III, and 3 Type II/N). / Our group has identified mutations in the SLC3A1 gene on 15 of 25 cystinuria chromosomes. All but one of these mutations have been found on patients with Type I/I phenotype (the remaining mutation was identified on a Type I/III patient). These studies have revealed eight mutations unique to Quebec and indicate population-specificity and genetic heterogeneity. Furthermore, SLC3A1 mutations only account for Type I cystinuria. However, since only 1 SLC3A1 mutation was identified in 9 Type I/III patients, the data suggest that another gene(s) is (are) responsible for the Type I/N phenotype in some patients.

No description available.

Several studies claim to have demonstrated an increased frequency of Down syndrome (DS) dermatoglyphics and other DS characteristics in parents of DS children, which could be explained by unrecognized parental mosaicism for trisomy 21. The goal of this study was to test the following hypothesis: In some cases of DS the cause will be parental gonadal mosaicism for trisomy 21. These parents will also be mosaic in tissues other than the gonads and will therefore have quantitative deviations in the direction of the DS phenotype. Upon examination of such traits in 162 parents with one DS child it was found that 22 parents had dermatoglyphic characteristics within the DS distribution of the Preus diagnostic index (no significant increase), 6 had DS quantitative phenotypic traits, and 1 had both. There was no evidence of bimodality in the distribution of these traits, or of a correlation between these traits with one another or with the Preus dermatoglyphic index for DS. There were no trisomy 21 cells in 200 lymphoblast cells counted for each of the 5 subjects with the most DS-like dermatoglyphic characteristics. The one subject who has both DS dermatoglyphics and a trend toward DS phenotype had 1/300 trisomy 21 cells in lymphoblast culture and 0/100 cells in fibroblast culture. Neither these data nor these from the literature, provide support for the suggestion that parental mosaicism for trisomy 21 is associated with an increase in DS-like physical characteristics.

Haemochromatosis is the most common single gene disorder to afflict North- West European populations. It is probably the most common genetic disorder of iron metabolism worldwide. As many as 1 in 250 people in the UK are affected and although the phenotype causes only a mild increase in gastrointestinal iron absorption a proportion of affected individuals will accumulate sufficient iron over their life-time to cause cirrhosis and hepatocellular carcinoma. Venesection treatment instituted before cirrhosis has established ensures a normal life expectancy, but clinical presentation is often late in life after irreversible organ injury has occurred. Identification of people at risk in the early, asymptomatic stage by measurements of iron status is unreliable. The genetic defect responsible for haemochromatosis has been sought in the hope that its identification might facilitate early diagnosis and that studies on the gene product would lead to a greater understanding of the mechanisms of mammalian iron absorption. Genetic linkage to HLA-A3 placed the gene responsible for haemchromatosis in, or close to, the major histocompatibilty complex (MHC) on the short arm of chromosome 6 and a positional cloning strategy has been adopted. This thesis describes work directed to the identification of the haemochromatosis gene by positional cloning. The region telomeric to the MHC was mapped using yeast artificial chromosomes, from which new microsatellites were isolated. These markers were used in linkage disequilibrium analyses and the mapping of a recombination breakpoint that defined a haemochromatosis gene region. This region was physically mapped in fine detail and positional candidates sought by EST database analysis. Before a systematic search for genes in the region began a strong positional candidate was reported (Feder et al 1996). Analysis of this mutation in patients from the UK confirmed this to be the ancestral haemochromatosis mutation.

There is now considerable evidence that endometriosis is likely to be a complex multifactorial trait, such as diabetes or asthma, in which a number of susceptibility loci interact with each other, and the environment, to produce the disease phenotype. This thesis presents studies on the genetic and environmental basis of endometriosis in both a non-human primate model and in women. The study of the autopsy records of 399 female rhesus monkeys identified 81 (20%) with spontaneous endometriosis. Age, exposure to ≥ 3 oestradiol implants (relative risk 9.7, P < 0.001) or ≥ 1 hysterotomy (relative risk 5.8, P = 0.006) were significant risk factors as determined by conditional logistic regression. Living descendants of the affected animals had MRI scans which suggested that 8/113 (7%) had at least one endometriotic lesion >1 cm in diameter. Segregation analysis was conducted on the resulting 12 pedigrees, which contained 64 half sib-pairs, 2 full sibpairs and 11 mother-daughter pairs. Human, affected sib-pairs and families were recruited for the OXEGENE study to conduct sib-pair analysis using microsatellite markers at 10cM resolution across the entire genome. MRI studies of the first-degree relatives of women with rAFS stage III-IV disease estimated that the relative risk (λ_R) may be as high as 14 (95% Cl 4.8 - 30.3). Candidate gene studies, comparing the frequency of the GALT N314D polymorphism, the CYP1A1 MspI polymorphism and the GSTM1 and T1 null mutations in two case groups, with either sporadic disease or a family history of endometriosis, and two control groups, did not show evidence of association. Linkage analysis using three microsatellite markers and 50 affected sib-pairs in the region to which GSTM1 maps (1p13) did not show evidence of linkage to this region. However, there was an apparent relationship between the presence of both the GSTM1 null mutation and the CYP1A1 MspI polymorphism and an increased risk of endometriosis. The initial findings of a sib-pair analysis, using 29 microsatellite markers across chromosome one in 128 affected sib-pairs, did not reveal evidence of linkage. These findings provide some insight into the aetiology of endometriosis in women.

No description available.

No description available.