POLYMORPHISM OF EXON-3 OF THE HLA-G GENE

HLA-G is a non-classical MHC class I gene with a limited tissue distri bution. The most pronounced expression is detected in the cytotrophobl ast of first trimester placenta. It is possible to detect mRNA for HLA -G in preimplantation blastocysts where expression is correlated with a high cleavage rate of embryos. HLA-G seems to play an important role in the fete-maternal relationship. The polymorphism of the HLA-G locu s is not fully clarified. One study has shown extensive nucleotide seq uence variation in the exon 3 (alpha-2 domain) in healthy African Amer icans. A few studies in other populations have only revealed a limited polymorphism. We investigated the polymorphism of the exon 3 of HLA-G by means of Polymerase Chain Reaction (PCR)- Single Strand Conformati on Polymorphism (SSCP)- and DNA sequencing analysis in a Danish popula tion. We detected four single-base substitutions in exon 3 compared to the sequence of HLA-6.0 (G01011); one of these has not been reported before. We also found a deletion of the first base of codon 130 or th e third of codon 129 in a heterozygous individual. This study, togethe r with previous results, suggests that the polymorphism of exon 3 of t he HLA-G gene in Caucasians is limited, in contrast to that observed i n Americans originating from Africa. Implications of this discrepancy and the detected deletion in relation to certain disorders of pregnanc y are discussed. (C) 1997 Elsevier Science Ireland Ltd.