Developmental and differential regulations in gene expression of Xenopus pleiotrophic factors-alpha and -beta.

Using conserved nucleotide sequences in mammalian osteoblast specific factor-1 (OSF-1) coding regions, we isolated two kinds of cDNA clones from the Xenopus brain library. The encoded proteins, named Xenopus pleiotrophic factors (X-PTFs)-alpha and -beta, were 65 and 87% homologous to human midkine and OSF-1, respectively. In the adult frog, X-ptf-alpha was expressed in the ovary, brain, eye, bone, heart and lung, whereas X-ptf-beta was expressed in the brain, eye and bone. By in situ hybridization of the tailbud embryo, X-ptf-alpha mRNA was detected rather broadly in the head/tail regions including the central nervous system (CNS), whereas X-ptf-beta mRNA was restricted to the CNS, particularly in the hind-brain. During embryogenesis, X-ptf-alpha mRNA was detected in the one-cell stage embryo, whereas only zygotic expression was observed in X-ptf-beta. X-ptf-beta mRNAs contained approximately 79 bp tandem repeats in the 3'-untranslated region, complementary to those found in retinoic acid cellular receptor mRNA and in the sense strand of short interspersed repeat transcripts in X. laevis.