Two isoforms of FTZ-F1 messenger RNA: molecular cloning and their expression in the frog testis

FTZ-F1, a member of the orphan nuclear receptors, is a transcriptional fact or regulating the expression of the fushi tarazu gene in Drosophila (Lavorg na et al., 1991. Science 252, 848-851). Previously, we cloned a frog homolo gue of FTZ-F1 (rrFTZ-F1 alpha; GenBank Accession No. AB035498). In this stu dy, we isolated the rrFTZ-F1 beta cDNA encoding a protein of 469 amino acid s. Then, expressions of two types (alpha and beta) of rrFTZ-F1 mRNAs were e xamined during development of embryos and gonads in the frog Rana rugosa. T hey were expressed in the embryo at stage 12. Expressions of both the alpha and beta mRNAs became stronger in the testis of frogs at stage XXV and wer e most prominent in that of frogs 2 months after metamorphosis. In the form er testis, spermatogonia were the only germ cells in the seminiferous tubul es, whilst postmeiotic cells were observed in the latter testis. Expression of the type alpha mRNA was more prominent. In addition, we cloned the regi ons with either exon I or II of the rrFTZ-F1 gene. Genomic structure analys is revealed that rrFTZ-F1 beta is a partial exon I-truncated variant of rrF TZ-F1 alpha. The results suggest that rrFTZ-F1 alpha and -beta are expresse d From the same gene by alternative splicing and that they may play an impo rtant role(s) in differentiation of premeiotic germ cells in the testis of the frog R rugosa. (C) 2000 Elsevier Science B.V. All rights reserved.