Evidence of H beta 58, a gene involved in mammalian placental development,in the three-toed skink, Chalcides chalcides (Squamata : Scincidae), a viviparous placentotrophic reptile

The H beta 58 gene, whose disruption in mice causes reabsorption of the emb ryo at 9.5 days post-conception, is believed to be essential for developmen t of the placenta. Although the H beta 58 gene is well conserved in some Am niota, nothing is known about its presence in reptiles, some species of whi ch have developed a chorioallantoic placenta. In this work, we investigated the expression of H beta 58 mRNA and protein in the three-toed skink, Chal cides chalcides. H beta 58 protein expression,vas found in the uterine epit helium beginning from the peri-ovulatory stage. However, it increased stron gly at the moment of placental formation, when a high level of expression o f mRNA and protein was also observed in the extra-embryonic membranes. The expression of H beta 58 mRNA and protein was maintained, although to a less er degree, in the placenta during late pregnancy. It was also present in th e early embryo. Finally, cloning and sequencing of a gene fragment revealed strong homology of the reptile gene with that of mammals. The high degree of conservation of the gene in amniote vertebrates and its presence in a vi viparous squamate reptile (as in mammals) indicates an important role of th is gene in the chorioallantoic placenta formation and development. (C) 2001 Harcourt Publishers Ltd.