RESUMO
BACKGROUND AND OBJECTIVES: The red blood cell Le(a-b-) phenotype was proposed as risk factor for type 1 diabetes, but contradictory results were published elsewhere. This study re-examined the potential association between Lewis histo-blood group system and type 1 diabetes. MATERIAL AND METHODS: Patients and controls of both sexes, Caucasians and non-Caucasians, matched by sex, geographical origin and ethnicity were evaluated. The red blood cell Lewis phenotypes were identified by gel column agglutination and also inferred from the FUT2 and FUT3 genotyping. RESULTS: The Le(a-b-) phenotype was prevalent in patients with type 1 diabetes, and the Le(a-b+) phenotype was prevalent in controls when both were determined by gel columns agglutination. No differences were observed in the frequencies of the Le(a-b-) phenotype inferred from the FUT2 and FUT3 genotyping between patients and controls. CONCLUSIONS: The Lewis red blood cell phenotyping and genotyping reveal divergence in the association of Le(a-b-) phenotype and type 1 diabetes.
Assuntos
Diabetes Mellitus Tipo 1/sangue , Genótipo , Antígenos do Grupo Sanguíneo de Lewis/genética , Fenótipo , Adolescente , Adulto , Estudos de Casos e Controles , Criança , Pré-Escolar , Feminino , Fucosiltransferases/genética , Humanos , Masculino , Pessoa de Meia-Idade , Galactosídeo 2-alfa-L-FucosiltransferaseRESUMO
The R337H TP53 mutation is a low-penetrance molecular defect that predisposes to adrenocortical tumour (ACT) formation in Brazilian and possibly other populations. Additional genetic defects may be responsible for the variable expression of ACTs in these cases. The inhibin alpha-subunit gene (INHA) on 2q33-qter has been implicated in mouse adrenocortical tumourigenesis. We studied 46 pediatric patients with ACTs from Brazil for INHA genetic alterations; 39 of these patients were heterozygous carriers of the R337H TP53 mutation. We first mapped the INHA gene by radiation hybrid analysis and determined 10 linked microsatellite markers in an area flanked by D2S1371 and D2S206 on 2q33-qter. These markers were then used for loss of heterozygozity (LOH) studies in nine paired germline and tumour DNA samples. Mapping placed the INHA gene in close proximity to D2S2848 (SHGC11864) with a log of odds (LOD) score of 5.84. LOH for at least one marker in the region was identified in 8/9 tumours (89%). Six patients were heterozygous for three INHA mutations: one in exon 1, 127C>G, and two in exon 2, 3998G>A and 4088G>A, all leading to amino acid substitutions (P43A, G227R, and A257T, respectively). A257T is located in a conserved INHA region, highly homologous to transforming growth factor-beta; both G227R and A257T change polarity, and, in addition, G227R changes the pH. We conclude that these sequence alterations and the detected 2q allelic changes suggest that INHA may be one of the contributing factors needed for ACT formation in pediatric patient carriers of the R337H TP53 mutation.