CLONING AND CHARACTERIZATION OF THE GENE ENCODING RED DEER (CERVUS-ELAPHUS) GROWTH-HORMONE - IMPLICATIONS FOR THE MOLECULAR EVOLUTION OF GROWTH-HORMONE IN ARTIODACTYLS

In mammals the structure of pituitary GH is generally strongly conserv ed, indicating a slow basal rate of molecular evolution. However, on t wo occasions, during the evolution of primates and of artiodactyls, th e rate of evolution has increased dramatically (25- to 50-fold) so tha t the sequences of human and ruminant GHs differ markedly from those o f other mammalian GHs. In order to define further the burst of GH evol ution that occurred in artiodactyls we have cloned and characterised t he GH gene of red deer (Cervus elaphus) using genomic DNA and a polyme rase chain reaction technique. The deduced sequence for the mature GH from red deer is identical to that of bovine GH, indicating that the b urst of rapid evolution of GH that occurred in Artiodactyla must have been completed before the divergence of Cervidae and Bovidae and sugge sting that the rate of evolution during this burst must have been grea ter than previously estimated. In other aspects (signal sequence, 5' a nd 3' sequences, introns and synonymous substitutions in the coding se quence) the red deer GH gene differs considerably from the GH genes of other ruminants. Differences between the signal peptide sequences of red deer and bovid GHs probably explain why N-terminal heterogeneity i s seen in bovine, ovine and caprine GHs but not GH from red deer, pig or most other mammals.