Evaluation of IP-RP-HPLC for length determination of the trinucleotide repeat fragments in Huntington's disease.

Expansion of an unstable trinucleotide (CAG)(n) repeat region within exon 1 of the gene IT15 causes autosomal, dominantly inherited Huntington's disease (HD). The number of CAG-repeats varies from 6 to 35 in normal individuals, whereas in affected patients the expanded allele contains 40 or more CAG-repeats. Thus, exact determination of both alleles of the gene (normal and expanded) on the molecular level is of great importance for clinical diagnosis and prognosis regarding the course of the disease. In our study, we optimized and evaluated a highly sensitive, automated, and economical molecular method for length characterization of the trinucleotide fragment expansion such as (CAG)(n) repeat region based on ion-pair reversed-phase high-performance liquid chromatography (IP-RP-HPLC). We found that IP-RP-HPLC can be used for exact fragment length measuring between 60-280 bp as a sensitive and advantageous alternative method to conventional techniques.

MYH Gene Status in Polish FAP Patients without APC Gene Mutations.

Familial Adenomatous Polyposis (FAP) is an inheritable predisposition for the occurrence of numerous polyps in the large intestine. In about 50% of all patients, the occurrence of the disease is conditioned by heterozygotic mutations of the APC gene. Screening for genetic factors in persons without mutations in the APC gene led to the identification of homozygotic mutations of the MYH gene as the cause of the appearance of the polyposis form which is characterized by recessive heritability and a milder course than in the case of the classic form of the disease. The authors examined 90 persons from the DNA bank of patients with FAP from the Institute of Human Genetics of the Polish Academy of Sciences in Poznan in whom no mutations in the APC gene were detected. Two of the most frequent mutations of the MYH gene (Y165C and G382D) were found to be heterozygous in 13% of patients and no other mutations in this gene coding sequence were observed. In the group with heterozygotic occurrence of the mutation in the MYH gene, the disease phenotype was not milder in comparison with the entire examined group and the mean age of the disease manifestation was even lower. This observation allows one to conclude that the employed methods of mutation screening were correct and, in the case of the examined group, the mutation ratio of the MYH gene does not precondition the occurrence of the disease, but it cannot be excluded that it may modify its phenotype. The obtained results indicate that the criteria applied during the process of FAP qualification are more rigorous than those applied in other countries.