Genetic assessment of familial and early-onset Parkinson's disease in a Greek population.

BACKGROUND AND PURPOSE: Although the first mutation associated with Parkinson's disease (PD) was identified several years ago in the alpha-synuclein (SNCA) gene in families of Greek and Italian ancestry, a more systematic study of this and other known PD mutations has not been performed in the Greek population. METHODS: A genetic analysis in 111 familial or sporadic with early-onset (≤50 years, EO) PD patients was performed for the presence of the A53T SNCA mutation. In separate subgroups of these patients, further mutations in the SNCA, LRRK2, Parkin, PINK1 and DJ-1 genes were searched for. Additionally, a subgroup of familial cases was analysed for mutations in the glucocerebrosidase (GBA) gene. RESULTS: In total, five patients (4.5% of our whole population) were identified with the A53T SNCA mutation, two with a heterozygote dosage mutation and one with a heterozygote point mutation in the Parkin gene, and seven patients (10.3% of our familial cohort) with GBA gene mutations. CONCLUSIONS: The A53T mutation in the SNCA gene, although uncommon, does represent a cause of PD in the Greek population, especially of familial EOPD with autosomal dominant inheritance. GBA mutations in the familial cohort tested here were as common as in a cohort of sporadic cases previously examined from the same centres. For the remainder of the genes, genetic defects that could definitively account for the disease were not identified. These results suggest that further Mendelian traits that lead to PD in the Greek population remain to be identified.

Contribution of BRCA1 germ-line mutations to breast cancer in Greece: a hospital-based study of 987 unselected breast cancer cases.

BACKGROUND: In most Western populations, 5-10% of all breast cancer cases can be attributed to major genetic factors such as predisposing mutations in BRCA1 and BRCA2, with early-onset cases generally considered as an indicator of genetic susceptibility. Specific BRCA1 and BRCA2 mutations or different mutation frequencies have been identified in specific populations and ethnic groups. Previous studies in Greek breast and/or ovarian cancer patients with family history have shown that four specific BRCA1 mutations, c.5266dupC, G1738R, and two large genomic rearrangements involving deletions of exons 20 and 24, have a prominent function in the population's BRCA1 and BRCA2 mutation spectrum. METHODS: To estimate the frequency of the above mutations in unselected Greek breast cancer women, we screened 987 unselected cases independently of their family history, collected from major Greek hospitals. RESULTS: Of the 987 patients, 26 (2.6%) were found to carry one of the above mutations in the BRCA1 gene: 13 carried the c.5266dupC mutation (1.3%), 6 carried the exon 24 deletion (0.6%), 3 carried the exon 20 deletion (0.3%), and 4 carried the G1738R mutation (0.4%). Among 140 patients with early-onset breast cancer (<40 years), 14 carried one of the four mutations (10.0%). CONCLUSION: These results suggest that a low-cost genetic screening for only the four prominent BRCA1 mutations may be advisable to all early-onset breast cancer patients of Greek origin.

Human hepatocyte nuclear factor-4 (hHNF-4) gene maps to 20q12-q13.1 between PLCG1 and D20S17.

Human hepatocyte nuclear factor 4 (hHNF-4) is a member of the nuclear hormone receptor superfamily and an important transcription factor and developmental regulator of liver-specific genes. Distinct hHNF-4 cDNAs corresponding to various HNF-4 isoforms have been recently characterised. Three cDNAs, hHNF-4A, B and C, are considered splice variants of a single hHNF-4 gene. We have mapped hHNF-4 to 20q12-q13.1 between PLCG1 and D20S17 by genetic linkage analysis, taking advantage of an adjacent PstI restriction fragment length polymorphism, (RFLP), and by fluorescence in situ hybridisation. hHFN-4 maps to chromosome 20 in a region syntenic with mouse chromosome 2 where the hnf-4 homologue has been assigned.

Map integration at human chromosome 10: molecular and cytogenetic analysis of a chromosome-specific somatic cell hybrid panel and genomic clones, based on a well-supported genetic map.

Well-characterized, chromosome-specific somatic cell hybrid panels are powerful tools for the analysis of the human genome. We have characterized a panel of human x hamster somatic cell hybrids retaining fragments of human chromosome 10 by fluorescence in situ hybridization and associated them to genetic markers. Most of the hybrids were generated by the radiation-reduction method, starting from a chromosome 10-specific monochromosomal hybrid, whereas some were collected from hybrids retaining chromosome 10-specific fragments as a result of spontaneous in vitro rearrangements. PCR was used to score the retention of 57 microsatellite markers evenly distributed along a well-supported framework genetic map containing 149 loci uniquely placed at 69 anchor points (odds exceeding 1,000:1), with an average spacing of 2.8 cM. As an additional resource for genomic studies involving human chromosome 10, we report the cytogenetic localization of a series of YAC and PAC clones recognized by at least one genetic marker. Somatic cell hybrids provide a powerful source of partial chromosome paints useful for detailed clinical cytogenetic and primate chromosome evolution investigations. Furthermore, correlation of the above physical, genetic, and cytogenetic data contribute to an emerging consensus map of human chromosome 10.

Genetic and physical mapping of five novel microsatellite markers on human Xp21.1-p11.22.

Five polymorphic CA-dinucleotide repeats, identified in cosmids from the short arm of the human X chromosome, have been characterized and localized to Xp21.1 (DXS572), Xp11.4 (DXS556, DXS574), and Xp11.22-p11.23 (DXS722, DXS573). Genetic mapping with respect to five reference markers that include the gene for CGD (CYBB in Xp21.1), complemented by physical mapping information, has indicated the order tel-DXS572-CYBB-DXS1110-DXS556-DXS574-D XS7-DXS426-DXS722-DXS573-DXS255-cen.

FISH mapping of 22 novel X chromosome cosmids and the isolation of a novel microsatellite on proximal Xp.

Twenty-two X-linked cosmid clones have been localised by fluorescence in situ hybridisation (FISH). Twelve map to the long arm of the X chromosome and 10 to the short arm. Seven of the latter cosmids and an additional one were mapped by two colour FISH relative to reference markers DXS7 and DXS426 in proximal Xp. Finer localisation of one of the cosmids, namely HX43 was achieved by isolation of a microsatellite followed by genetic mapping with respect to reference markers in the region.

Isolation and characterization of three microsatellite markers in the proximal long arm of the human X chromosome.

Three microsatellites have been identified in cosmids from the human X chromosome. The cosmids have been assigned locus numbers DXS554, DXS559, and DXS566 and have been localized to Xq12-q13 (DXS554 and DXS559) and Xq13 (DXS566). In addition, they have been genetically mapped in relation to the androgen receptor (AR), phosphoglycerate kinase 1, pseudogene 1 (PGK1P1), and phosphoglycerate kinase (PGK1) loci in the proximal long arm. Genetically, the localization of microsatellites at DXS554 and DXS566 is indistinguishable from PGK1, whereas that at DXS559 maps between AR and PGK1, close to PGK1P1. DXS566 is identical to the independently identified DXS441 marker. These markers should be useful for physical and genetic mapping in this region.

X chromosome linkage studies in familial Rett syndrome.

Four families, each with two individuals affected by Rett Syndrome (RS), were analysed using restriction fragment length polymorphisms and microsatellite markers from the X chromosome. In two of the families, X-linked dominant inheritance of the RS defect from a germinally mosaic mother could be assumed. Therefore, maternal X chromosome markers showing discordant inheritance were used to exclude regions of the X chromosome as locations of the RS gene. Much of the short arm could be excluded, including regions containing three candidate genes, OTC, synapsin 1 and synaptophysin. Although most of the long arm was inherited in common it was possible to exclude a centromeric region. Inheritance of X chromosome markers is also presented for two families with affected aunt-niece pairs, one of which has not been previously studied at the DNA level.

The gene for Aarskog syndrome is located between DXS255 and DXS566 (Xp11.2-Xq13).

Aarskog syndrome has been mapped to Xq13 on the basis of a patient carrying an Xq13:8p21.2 translocation. We have identified a new microsatellite marker in a clone mapping to this region (HX60;DXS566). Using primers flanking this microsatellite along with primers detecting a microsatellite at PGK1P1 and DXS255, and DXS72, we have performed a multipoint analysis in a large kindred with Aarskog syndrome. Our results suggest that the Aarskog locus lies proximal to Xq13. This is supported by the recent redefining of the breakpoint of the original translocation as between DXS14 (Xp11.21-p11.1) and DXS146 (Xp11.23-p11.22).