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Schizophrenia is a complex disease affecting as much as 1% of the global population, constituting the target of considerable effort to identify disease susceptibility genes. Several lines of evidence point to the catechol-O-methyl-transferase (COMT) gene as a schizophrenia susceptibility candidate, not only because it encodes a key dopamine catabolic enzyme but also because it maps to the velocardiofacial syndrome region of chromosome 22q11, which has long been associated with predisposition to the disease. Several case-control and family-based studies have been conducted to examine the possible association of COMT with this disorder; however , these studies have produced conflicting results. To further assess the genetic contribution of COMT variants to schizophrenia susceptibility, three single-nucleotide polymorphisms (rs2075507, rs4680 and rs362204) were investigated in a sample of 74 family trios from the Cuban population. Restriction fragment length polymorphism was used to identify the allelic variants, employing statistical tools based on transmission disequilibrium tests to find possible associations. In this study, the first of its type performed in the Cuban population, we found an association of rs2075507 and rs362204 at allelic levels with a p < 0.05; also finding an association of haplotype 1-2-1 with the disease. [ABSTRACT FROM AUTHOR]

The article discusses Human Leukocyte Antigen (HLA) and deoxyribonucleic acid typing methods. Genes on the short arm of chromosome six control the HLA. The HLA loci is included in the genetic region known as the major histocompatibility complex (MHC). The identification of HLA antigens is referred as tissue typing.

Short nucleotide repetitions (STRs) are commonly used as genetic markers; thus their detection and analysis constitutes a very important tool for the mapping of genetic diseases, as well as for gathering information about genetic polymorphisms at the population level. STRs can be detected with agarose- or acrylamide-based electrophoretic techniques, followed by visualization of the DNA sample with ethidium bromide, silver nitrate, or fluorophore labeling. In this work, we analyzed genomic DNA from five individuals affected with type II diabetes mellitus (T2DM) and five controls (unaffected individuals) in order to know the most precise and reproducible technique for the analysis of the existing polymorphism in the STR DG10S478 of the TCF7L2 gene. The combination of PCR with labeling of the products with the CY5 fluorophore, followed by detection on an ALFexpress sequencer, offered the required resolution to detect the variability in this STR, based solely on size analysis. Our methodology offers similar accuracy and reproducibility at lower costs than existing methods based on the sequencing of PCR products, and is a faster alternative when applied to genotyping studies.