Differential Splicing and Expression of the Relaxin-Like Factor Gene in Reproductive Tissues of the Marmoset Monkey (Callithrix jacchus)1

The relaxin-like factor (RLF) is a novel member of the insulin/relaxin/insulin-like growth factor family of growth factors and hormones that is expressed predominantly in the reproductive system, with highest expression in the Leydig cells of the testis. Using a combination of molecular and immunological techniques, we have characterized the structure and expression of the RLF gene from a primate model, the marmoset monkey, with the intention of comparing this with recent results on the closely related hormone relaxin in this species. As in other species, including the human, RLF gene products can be detected maximally in Leydig cells and in the follicular theca interna cells and corpora lutea of the ovary. Reverse transcription-polymerase chain reaction analysis confirmed this expression and showed that in the corpus luteum, testis, and epididymis, a second, alternative RLF gene transcript was present that is expressed at low levels and that appears to be derived by differential splicing of a novel exon. Analysis of genomic DNA from the marmoset showed that in this species, the single-copy gene contains a longer intronic region separating the two exons described for the human. Alternative splicing introduces a novel exon 1A between exons 1 and 2, which leads to an altered open reading frame, with a new stop codon, such that if translated, the novel transcript will encode a truncated polypeptide comprising a C-terminally extended B-domain.