H ereditary non-polyposis colorectal cancer (HNPCC, Lynch syndrome) is an autosomal dominantly inherited syndrome predisposing to the early development of cancers of the colon, rectum, endometrium, small bowel, and urinary tract and accounts for ∼5% of all colon cancer cases.1 There are at least five genes involved in this cancer predisposition and they include MLH1, 2 MSH2, 3 MSH6, 4 PMS2, and PMS1.5 Currently, more than 300 different mutations have been described in these genes which account for approximately 500 HNPCC kindreds from different parts of the world.6 MLH1 and MSH2 genes show abnormalities in more than 90% of HNPCC families with identified germline mutations 7 (http://www.nfdht.nl). The majority of reported MLH1 and MSH2 mutations are dispersed throughout the 35 exons of these two genes. However, some changes are recurrent and are described as founder mutations in particular populations. [8][9][10][11] In order to develop efficient DNA testing, it is important to describe the nature and frequency of mutations that are characteristic of particular ethnic groups. The MSH2 and MLH1 mutation spectrum has not been investigated in the eastern European region and therefore there is no knowledge about any recurrent mutations which may significantly aid in the mutation screening procedures for this region. Here, we describe the results of DNA/RNA based mutation sequencing of both the MSH2 and MLH1 genes in a series of HNPCC families from Poland (89 cases) and the Baltic States (12 cases). MATERIAL AND METHODS PatientsA total of 101 unrelated patients affected by colorectal cancer or an HNPCC associated cancer (endometrium, small bowel, urinary tract) were from 17 families which fulfilled the Amsterdam II criteria 12 and from 84 families matching our modified criteria of suspected HNPCC, one colorectal cancer patient with a first degree relative affected by an HNPCC associated cancer, one of whom was diagnosed under the age of 50 years. 13 The clinical diagnosis of HNPCC was established or verified at the Hereditary Cancer Centre, Pomeranian Academy of Medicine, Szczecin, Poland. Patients used for this study were ascertained from the following regions: Bydgoszcz (3), Gdańsk (3), Kielce (14), Kraków (3), Legnica (1), Lublin (2), Lódz (1), Olsztyn (13), Poznań (7), Riga (3), Szczecin (33), Tartu (3), Wrocław (5), Vilnius (6), Zielona Góra (4). DNA isolationPeripheral blood samples were collected from the patients after obtaining informed consent. DNA was extracted directly from leucocytes by the classical phenol purification method or as described previously.14 DNA sequencing All exons and exon-intron junctions of MLH1 and MSH2 were amplified using the same protocols as described previously 15 with the same primer sequences as described by Wijnen et al 16 17 for DGGE but without the M13 and GC clamp sequences at the 5′ end. Dye terminator cycle sequencing reactions were performed using the ABI PRISM Dye-terminator Cycle Sequencing Ready Reaction kit (Perkin Elmer) according to the manufacturer's recommended p...

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Lithuanian patients with visual problems were clinically examined for retinitis pigmentosa (RP). A total of 33 unrelated families with autosomal dominant RP (adRP) were identified. Screening for mutations in the rhodopsin (RHO) and peripherin/RDS (RDS) genes was performed using DNA heteroduplex analysis. Direct DNA sequencing in the cases of heteroduplex formation showed the presence of the following mutations and polymorphisms in 14 adRP patients: RHO gene – Lys248Arg (1 case), and Pro347Leu (2 cases); RDS gene – Glu304Gln (12 cases), Lys310Arg (5 cases), and Gly338Asp (12 cases). The presence of these mutations (except Lys248Arg in the RHO gene) was confirmed by relevant restriction enzyme digestion. The frequency of the RDS gene mutations Glu304Gln and Gly338Asp was estimated to be 36.4%, while mutation Lys310Arg was less frequent (15.2%). These 3 RDS gene mutations appear to be polypeptide polymorphisms not related to adRP.

Background. In the scientific literature, a wide range of effect variants that protect against complex disease phenotypes has been identified. Analysis of these variants and overall genetic structure of isolated or, in our case, small populations is important in association analysis. When analysing admixture populations during GWAS, one could expect inaccuracies, which could be eliminated by choosing distinct populations as one of the interests of study. Population genetic structure determines similarities and differences between individuals or different groups of individuals and the factors that may lead to those differences. Results. In our study, we identified six missense effect variants in the Lithuanian population having frequencies that were significantly different compared to other European populations. Three of these effect variants may potentially protect against type 2 diabetes and coronary heart disease.Conclusions. Even though high rates of these diseases in the Lithuanian population and other populations indicates the presence of environmental factors and the lack of knowledge about the interactions between regulatory regions and other effect variants. Identification of these effect variants is important not only to provide a better understanding of the microevolutionary processes and etiopathogenetic mechanisms, but also to develop disease prevention programs and novel, personalised therapies using genome editing or other genetic tools.