ABSTRACT
Down syndrome (DS) is a complex genetic and metabolic disorder attributed to the presence of three copies of chromosome 21. The extra chromosome derives from the mother in 93% of cases and is due to abnormal chromosome segregation during meiosis (nondisjunction). Except for advanced age at conception, maternal risk factors for meiotic nondisjunction are not well established. A recent preliminary study suggested that abnormal folate metabolism and the 677 (C-->T) mutation in the methylene-tetrahydrofolate reductase (MTHFR) gene may be maternal risk factors for DS. Frequency of the MTHFR 677 (C-->T) and 1298 (A-->C) mutations was evaluated in 36 mothers of children with DS and in 200 controls. The results are consistent with the observation that the MTHFR 677 (C-->T) and 1298 (A-->C) mutations are more prevalent among mothers of children with DS than controls. In addition, the most prevalent genotype was the combination of both mutations. The results suggest that mutations in the MTHFR gene are associated with maternal risk for DS
Subject(s)
Down Syndrome/genetics , Genetic Predisposition to Disease/genetics , Mutation , Oxidoreductases Acting on CH-NH Group Donors/genetics , Adolescent , Adult , Alleles , Case-Control Studies , Down Syndrome/enzymology , Female , Genotype , Humans , Methylenetetrahydrofolate Reductase (NADPH2) , Oxidoreductases Acting on CH-NH Group Donors/metabolism , Risk FactorsABSTRACT
Sindrome de Down (SD) é uma alteraçäo genética e metabólica complexa atribuída à presença de três cópias do cromossomo 21. O cromossomo extra em 93 por cento dos casos é de origem materna e é resultante de uma segregaçäo anormal durante a meiose (näo-disjunçäo). Com exceçäo da idade materna avançada, fatores de risco para a näo-disjunçäo meiótica näo estäo bem estabelecidos. Um estudo preliminar sugeriu que o metabolismo anormal do folato e a mutaçäo 677 (C->T) no gene da metilenotetrahidrofolato redutase (MTHFR) podem ser fatores de risco maternos para a SD. A freqüência das mutaçöes MTHFR 677 (C->T) e 1.298 (A->C) foram avaliadas em 36 mäes de crianças com SD e em 200 indivíduos-controle. Os resultados demonstraram que as mutaçöes 677 (C->T) e 1.298 (A->C) säo mais prevalentes entre mäes de crianças com SD do que nos controles. A heterozigose das duas mutaçöes foi a combinaçäo mais freqüente. O resultado desse estudo inicial sugere que mutaçöes no gene da MTHFR seriam um fator de risco para a SD
