Association of HLA Alleles with Primary Sjögren Syndrome in the South Tunisian Population.

OBJECTIVE: In order to investigate human leukocyte antigen (HLA) genes predisposing to primary Sjögren syndrome (pSS), we conducted an association study using HLA loci (A, B, and DRB1) and 9 polymorphic microsatellite markers spanning the HLA region in pSS patients as compared to healthy individuals. SUBJECTS AND METHODS: Forty-four patients fitting the European criteria of pSS and 123 healthy controls were analyzed for their HLA class I and class II alleles. HLA class I typing was performed using a standard microlymphocytotoxicity method followed by PCR-SSP. HLA-DRB1 genotyping was performed using PCR-SSP. We studied the polymorphism of 9 microsatellite markers for both groups. Microsatellite genotyping was performed using the PCR fluorescent technique. RESULTS: We observed a positive association between HLA-B15 and pSS in the Tunisian population (p = 0.004, OR 7.57). The comparison of the frequencies of DRB1 alleles in pSS patients and controls confirmed the association of the DRB1*03 allele with pSS (p = 0.02, OR 2.36). On the other hand, the association study of microsatellite markers showed that the a9 allele of D6S265 marker and the a20 of C1.2.C were found to be positively associated with pSS as compared to controls (p =0.0003, OR 10.29, and p =0.001, OR 4.79, respectively). Using the "Haplo.stats" software analysis, we found that the most associated region was located in the HLA class I region and limited by HLA-A and D6S265 loci (p = 0.00056). CONCLUSION: The results of this study support the hypothesis of the existence of a susceptibility gene for pSS located in the HLA class I and III regions.

Genetic diversity and haplotype structure of 21 Y-STRs, including nine noncore loci, in South Tunisian Population: Forensic relevance.

Y chromosome STRs (Y-STRs) are being used frequently in forensic laboratories. Previous studies of Y-STR polymorphisms in different groups of the Tunisian population identified low levels of diversity and discrimination capacity (DC) using various commercial marker sets. This definitely limits the use of such systems for Y-STRs genotyping in Tunisia. In our investigation on South Tunisia, 200 unrelated males were typed for the 12 conventional Y-STRs included in the PowerPlex® Y System. Additional set of nine noncore Y-STRs including DYS446, DYS456, DYS458, DYS388, DYS444, DYS445, DYS449, DYS710, and DYS464 markers were genotyped and evaluated for their potential in improving DC. Allele frequency, gene diversity, haplotype diversity (HD), and DC calculation revealed that DYS464 was the most diverse marker followed by DYS710 and DYS449 markers. The standard panel of 12 Y-STRs (DC = 80.5%) and the nine markers were combined to obtain DC of 99%. Among the 198 different haplotypes observed, 196 haplotypes were unique (HD = 99.999). Out of the nine noncore set, six Y-STRs (DYS458, DYS456, DYS449, DYS710, DYS444, and DYS464) had the greatest impact on enhancing DC. Our data provided putative Y-STRs combination to be used for genetic and forensic applications.

Analysis of HLA-A, -B, -C, -DR, -DQ polymorphisms in the South Tunisian population and a comparison with other populations.

BACKGROUND: The Human Leucocyte Antigen (HLA) system is often used as a genetic marker for analysing populations. HLA antigen distribution among the Tunisian population is not well defined because of the lack of a general population study. AIM: The aim of the present study was to investigate the polymorphism of HLA-A, -B, -C, -DR and -DQ loci in the South Tunisian population. SUBJECTS AND METHODS: This study has investigated HLA-A, -B, -C, -DR and -DQ polymorphisms in 123 unrelated healthy individuals originating from the south of Tunisia. HLA class I was studied by serology and completed by polymerase chain reaction-sequence specific primer (PCR-SSP). HLA class II was performed using PCR-SSP. RESULTS: The most common alleles were A-2 (0.2154), B-44 (0.1179), C7 (0.2114), DR4 (0.1626) and DQ2 (0.313). A1-B-8-C7-DR3-DQ2 (2.84%) was the predominant haplotype in this population. Comparisons with data of other worldwide populations based on phylogenetic tree and multidimensional scaling analysis were done. This study suggests that both HLA class I and class II polymorphism specificities demonstrate a high diversity in this South Tunisian population, which reflects ancient and recent admixture with neighbouring populations. CONCLUSION: The results provide useful information for further studies of Tunisian population evolution, anthropology and for resolving HLA frequencies when searching for HLA-compatible donors in transplantation and for the analysis of disease associations.