No association of the ACTN3 gene R577X polymorphism with endurance performance in Ironman Triathlons.

Alpha-actinins are major structural components of the Z-discs in skeletal muscle. Alpha-actinin 3 is encoded by the ACTN3 gene and is expressed only in type II muscle fibres. Homozygosity for the nonsense mutation, 577X, within ACTN3 results in deficiency of alpha-actinin-3 but does not result in an abnormal muscular phenotype. Previous research has found an association of the 577R allele with sprinting and/or power performance. It has also been suggested that the 577X allele may confer an advantage during endurance events. Four hundred and fifty seven Caucasian male triathletes who completed either the 2000 and/or 2001 226 km South African Ironman Triathlons, and 143 Caucasian controls, were genotyped for the R577X mutation within the ACTN3 gene. There were no significant differences in either the genotype (P = 0.486) or allele (P = 0.375) frequencies within the fastest, middle of the field or slowest Caucasian male finishers and the control population. In conclusion, the R577X polymorphism within the ACTN3 gene was not associated with ultra-endurance performance in the 2000 and 2001 South African Ironman Triathlons.

Spectrum and prevalence of prothrombotic single nucleotide polymorphism profiles in the Greek Cypriot population.

BACKGROUND: This study was performed to establish the allele, genotype and genotype combination/SNP (single nucleotide polymorphism) profile frequencies in the general population of Cyprus for 6 genes implicated in thrombotic disorders. The genes with their respective functional polymorphisms were the following: factor V (G1691A), prothrombin/factor II (G20210A), methylenetetrahydrofolate reductase (C677T), platelet glycoprotein receptor IIIa (P1A1/A2), b-fibrinogen (G/A-455) and plasminogen activator inhibitor-type 1 (4G/5G). METHODS: DNA samples from 121 unrelated individuals were used for this epidemiological study. The polymerase chain reaction followed by restriction digestion were used to genotype the 6 different polymorphic loci. Allele and genotype frequencies were established and shown to be in Hardy-Weinberg equilibrium. RESULTS: Mutant allele frequencies for the 6 genes were as follows: factor V-4%, prothrombin-2%, methylenetetrahydrofolate reductase -39%, platelet glycoprotein receptor IIIa-16%, beta-fibrinogen-17% and plasminogen activator inhibitor - type 1-46%. Combined defects occurred which may increase the risk for vascular events, 33% of individuals (39/118) had 3 or more of the above mutations. CONCLUSIONS: As in other European populations, prospective case-control studies to estimate the risk for deep vein thrombosis (DVT) and ischemic episodes with respect to genetic and environmental risk factors should be performed. Thrombophilia screening should be applied for primary and secondary prevention of thrombotic episodes in susceptible individuals on the island of Cyprus. Individuals targeted for such screening include those with the following: a positive family history for thrombosis; a previous DVT or other ischemic episode; prior exposure to circumstantial risk factors and in the presence of echolucent plaques.

Characterization and geographic distribution of the low density lipoprotein receptor (LDLR) gene mutations in northwestern Greece.

Familial Hypercholesterolaemia (FH) is a clinical syndrome characterised by elevated serum total cholesterol levels due to an increase in low density lipoprotein (LDL) cholesterol, by tendon xanthomata and clinical manifestations of ischaemic heart disease in early life. Typically, it results from mutations in the low-density lipoprotein receptor (LDLR) gene. So far, over 600 mutations have been reported for the LDLR gene and account for FH. The nature of LDLR gene mutations is different in various ethnicities and has also regional distribution within each ethnicity. Eleven mutations have already been described in the Greek population. This report describes seven LDLR gene mutations accounting for FH in Northwestern Greece (81T>G, 517T>C, 858C>A, 1285G>A, 1352T>C, 1646G>A and 1775G>A) and their geographic distribution. We have recently described one of these mutations (1352T>C) as a novel point mutation in a Greek family originating from Northwestern Greece. Furthermore, two previously identified mutations (81T>C, 1775G>A) were also detected in the Greek FH patients for the first time. The 1775G>A mutation was responsible for all the homozygous patients in our area, indicating a founder effect. These data will favor the development of tailed information and screening programs in Northwestern Greece for the primary prevention of cardiovascular disease in FH patients.

Geographical clustering of low density lipoprotein receptor gene mutations (C292X; Q363X; D365E & C660X) in Cyprus.

In Cyprus, no data are yet available on the frequencies of clinically diagnosed FH patients. Further, until now, familial hypercholesterolaemia in Cyprus had not been studied at the molecular level to determine the nature or frequency of LDLR gene mutations. Being a relatively homogeneous population, we anticipated that a few founder mutations would predominate on the island. In the present study, three previously identified LDLR gene mutations were found to cosegregate with high LDL cholesterol levels in 23 unrelated, clinically diagnosed families with FH. Geographical clustering of each of these LDLR gene mutations was indicated, a phenomenon arising from low migration rates and high inbreeding. The latter cultural practices account for the discovery of a homozygous FH sib pair whose parents are carriers of the same mutation. Microsatellite and intragenic haplotype analysis in this FH population, suggested that the families which shared the same LDLR gene mutation have a common origin. This is supported by their relative geographical distribution. Thirty young FH individuals were also offered presymptomatic diagnosis which should facilitate the prevention of premature coronary artery disease. Finally, results from this study support the suggestion that the formation of tendon xanthomata in FH patients may be under environmental influence. Hum Mutat 15:380, 2000.

PKD2, a gene for polycystic kidney disease that encodes an integral membrane protein.

A second gene for autosomal dominant polycystic kidney disease was identified by positional cloning. Nonsense mutations in this gene (PKD2) segregated with the disease in three PKD2 families. The predicted 968-amino acid sequence of the PKD2 gene product has six transmembrane spans with intracellular amino- and carboxyl-termini. The PKD2 protein has amino acid similarity with PKD1, the Caenorhabditis elegans homolog of PKD1, and the family of voltage-activated calcium (and sodium) channels, and it contains a potential calcium-binding domain.