Association of HLA-G 3' untranslated region variants with type 1 diabetes mellitus

Besides the well recognized association of HLA-DRB1 and DQB1 alleles with type 1 diabetes mellitus (T1D), linkage studies have identified a gene region close to the non-classical class I HLA-G gene as an independent susceptibility marker. HLA-G is constitutively expressed in the endocrine compartment of the human pancreas and may play a role in controlling autoimmune responses. We evaluated the genetic diversity of the 3' untranslated region (3'UTR) of HLA-G, which have been associated with HLA-G mRNA post-transcriptional regulation, in 120 Brazilian T1D patients and in 120 healthy controls. We found the +3001 T allele was observed only in T1D patients. Notably, the +3001 T allele was in linkage disequilibrium with polymorphic sites associated with low production of HLA-G mRNA or soluble HLA-G levels. Moreover, T1D patients showed a low frequency of the HLA-G 3'UTR-17 (14bpINS/+3001T/+3003T/+3010C/+3027C/+3035T/+3142G/+3187A/+3196C). The +3010 CC genotype and the UTR-3 haplotype (14bpDEL/+3001C/+3003T/+3010C/+3027C/+3035C/+3142G/+3187A/+3196C), associated with low and moderate soluble HLA-G expression, respectively, were underrepresented in patients. The decreased expression of HLA-G at the pancreas level should be detrimental in individuals genetically prone to produce less HLA-G.