Expression analysis and cloning of mouse protocadherin 10 isoforms /

Master of Science in de biochemie en de biotechnologi

Variant ataxia telangiectasia: clinical and molecular findings and evaluation of radiosensitive phenotypes in a patient and relatives

Variant ataxia telangiectasia (A-T) may be an underdiagnosed entity. We correlate data from radiosensitivity and kinase assays with clinical and molecular data from a patient with variant A-T and relatives. The coding region of ATM was sequenced. To evaluate the functional effect of the mutations, we performed kinase assays and developed a novel S-G2 micronucleus test. Our patient presented with mild dystonia, moderately dysarthric speech, increased serum alpha-fetoprotein but no ataxia nor telangiectasias, no nystagmus or oculomotor dyspraxia. She has a severe IgA deficiency, but does not have recurrent infections. She is compound heterozygote for ATM c.8122G > A (p.Asp2708Asn) and c.8851-1G > T, leading to in frame loss of 63 nucleotides at the cDNA level. A trace amount of ATM protein is translated from both alleles. Residual kinase activity is derived only from the p.Asp2708Asn allele. The conventional G0 micronucleus test, based on irradiation of resting lymphocytes, revealed a radiosensitive phenotype for the patient, but not for the heterozygous relatives. As ATM is involved in homologous recombination and G2/M cell cycle checkpoint, we optimized an S-G2 micronucleus assay, allowing to evaluate micronuclei in lymphocytes irradiated in the S and G2 phases. This test showed increased radiosensitivity for both the patient and the heterozygous carriers. Intriguingly, heterozygous carriers of c.8851-1G > T (mutation associated with absence of kinase activity) showed a stronger radiosensitive phenotype with this assay than heterozygous carriers of p.Asp2708Asn (mutation associated with residual kinase activity). The modified S-G2 micronucleus assay provided phenotypic insight into complement the diagnosis of this atypical A-T patient

Evaluation of RAD51C as cancer susceptibility gene in a large breast-ovarian cancer patient population referred for genetic testing

Despite extensive analysis of the BRCA1 and BRCA2 genes, germline mutations are detected in < 20% of families with a presumed genetic predisposition for breast and ovarian cancer. Recent literature reported RAD51C as a new breast cancer susceptibility gene. In this study, we report the analysis of 410 patients from 351 unrelated pedigrees. All were referred for genetic testing and we selected families with at least one reported case of ovarian cancer in which BRCA1&2 mutations were previously ruled out. We analyzed the coding exons, intron-exons boundaries, and UTRs of RAD51C. Our mutation analysis did not reveal any unequivocal deleterious mutation. In total 12 unique sequence variations were identified of which two were novel. Our study and others suggest a low prevalence of RAD51C mutations with an exception for some founder populations. This observation is in favor of the rare allele hypothesis in the debate over the nature of the genetic contribution to individual susceptibility to breast and ovarian cancer and further genome-wide studies in high risk families are warranted