Absence of the genetic variant Val79Met in human chorionic gonadotropin-beta gene 5 in five European populations

Chorionic gonadotropin (CG) is an essential signal in establishment and maintenance of pregnancy in humans and higher primates. A G-to-A transition in exon 3 of human CGbeta gene 5, changing the naturally occurring valine residue to methionine in codon 79 (Val(79)Met) has been reported at carrier frequency 4.2% in a random population from the Midwest of the United States. The biological activity of the variant hCG was similar to that of wild-type (WT) hCG. However, the Val(79)Met beta-subunit displayed impaired ability to assemble with alpha-subunit, and the amount of hCG alpha/beta heterodimers formed and secreted by transfected cells was seriously impaired in the previous study. Because of these functional implications we found it important to study the occurrence of the Val(79)Met hCGbeta variant in other populations. By using a PCR-RFLP method, a search for the Val(79)Met hCGbeta variant was carried out on a total of 580 DNA samples from five European populations (Finland, Denmark, Greece, Germany and the UK). The results demonstrated an absence of the polymorphism in these populations. Hence, the naturally occurring variant (Val(79)Met) of the hCGbeta gene 5, found previously at high frequency in the US, is clearly less common, or absent, in the European populations studied.