MSX1 gene and nonsyndromic oral clefts in a Southern Brazilian population

Nonsyndromic oral clefts (NSOC) are the most common craniofacial birth defects in humans. The etiology of NSOC is complex, involving both genetic and environmental factors. Several genes that play a role in cellular proliferation, differentiation, and apoptosis have been associated with clefting. For example, variations in the homeobox gene family member MSX1, including a CA repeat located within its single intron, may play a role in clefting. The aim of this study was to investigate the association between MSX1 CA repeat polymorphism and NSOC in a Southern Brazilian population using a case-parent triad design. We studied 182 nuclear families with NSOC recruited from the Hospital de Clínicas de Porto Alegre in Southern Brazil. The polymorphic region was amplified by the polymerase chain reaction and analyzed by using an automated sequencer. Among the 182 families studied, four different alleles were observed, at frequencies of 0.057 (175 bp), 0.169 (173 bp), 0.096 (171 bp) and 0.67 (169 bp). A transmission disequilibrium test with a family-based association test (FBAT) software program was used for analysis. FBAT analysis showed overtransmission of the 169 bp allele in NSOC (P=0.0005). These results suggest that the CA repeat polymorphism of the MSX1 gene may play a role in risk of NSOC in populations from Southern Brazil.

Genetics of homocysteine metabolism and associated disorders

Homocysteine is a sulfur-containing amino acid derived from the metabolism of methionine, an essential amino acid, and is metabolized by one of two pathways: remethylation or transsulfuration. Abnormalities of these pathways lead to hyperhomocysteinemia. Hyperhomocysteinemia is observed in approximately 5 percent of the general population and is associated with an increased risk for many disorders, including vascular and neurodegenerative diseases, autoimmune disorders, birth defects, diabetes, renal disease, osteoporosis, neuropsychiatric disorders, and cancer. We review here the correlation between homocysteine metabolism and the disorders described above with genetic variants on genes coding for enzymes of homocysteine metabolism relevant to clinical practice, especially common variants of the MTHFR gene, 677C>T and 1298A>C. We also discuss the management of hyperhomocysteinemia with folic acid supplementation and fortification of folic acid and the impact of a decrease in the prevalence of congenital anomalies and a decline in the incidence of stroke mortality.

Polymorphisms in genes MTHFR, MTR and MTRR are not risk factors for cleft lip/palate in South Brazil

Non-syndromic cleft lip and palate (CL/P) occurs due to interaction between genetic and environmental factors. Abnormalities in homocysteine metabolism may play a role in its etiology due to polymorphisms in genes involved in this pathway. Because of the involvement of MTHFR, MTR and MTRR genes with folate metabolism and the evidence that maternal use of folic acid in early pregnancy reduces the risk for CL/P, we evaluated the influence of their polymorphisms on the etiology of CL/P through a case-control study. The analyses involved 114 non-syndromic phenotypically white children with clefts (case) and 110 mothers, and 100 non-affected (control) children and their mothers. The polymorphisms 677C>T of MTHFR, 2756A>G of MTR, and 66A>G of MTRR genes were analyzed by PCR-RFLP. Allelic frequencies did not differ from other studies conducted on white populations for MTHFR 677T allele (0.35) and for MTR 2756G allele (0.17), but MTRR 66G allele frequency (0.35) was lower than observed elsewhere. The genotypic distribution of the 677C>T polymorphisms under study did not show significant differences between CL/P patients, their mothers and controls. These results suggest that the alterations of folate metabolism related to these polymorphisms are not involved in clefting in the population under study.