Comparison of chorionic gonadotropin expression in human and macaque (Macaca fascicularis) trophoblasts

We have designed novel DNA primers that allow us to detect the expression of the subunits of chorionic gonadotropin (CG) from a variety of species of the order Primates. Using these primers, reverse transcriptase-polymerase chain reaction (RT-PCR), and standard cloning techniques, we detected the expression of a single gene for the common glycoprotein hormone (GPH) alpha-subunit and at least two genes for the CG beta-subunit in trophoblasts of Macaca fascicularis (cynomolgous macaque (cm)) at gestational day (GD) = 26 (+/- 2d). No cmCG expression was detected at GD = 35-40. When sequences of cmGPH-alpha and cmCG-beta genes were compared to the corresponding genes of other primates, we found that the alpha-subunit of M. fascicularis was highly conserved compared to other primate species. However, cmCG beta-subunits appeared to be less conserved, residing between those of human CG-beta and baboon CG-beta when analyzed phylogenetically. Of particular interest was a three amino acid stretch in one of the expressed cmCG-beta genes that is distinct from all other primates studied. Our findings imply that not only does the expression of multiple CG beta-subunit genes appear to be common to Old World monkeys, but that the presented methodology will greatly facilitate our ability to understand primate evolution.