Expression and regulation of relaxin-like factor gene transcripts in the bovine ovary: Differentiation-dependent expression in theca cell cultures

The relaxin-like factor (RLF) was recently discovered as a new member of th e insulin-insulin-like growth factor-relaxin family of growth factors and h ormones predominantly in the Leydig cells of the testis. In cattle, in cont rast to other species, the RLF gene is also expressed to a high level in th e ovary, where its expression pattern in the corpus luteum of the late cycl e and pregnancy is similar to that of relaxin in the pig. The RLF gene was also transcribed to a high level in the theca cells of estrogen-rich, large antral follicles. Long-term primary cultures of bovine theca cells showed that expression was insulin dependent. After an initial decline in specific mRNA concentrations, there was a switch to a transcript with a longer poly (A) tail at about Day 6 of culture, which continued to increase to very hig h levels by Day 15 of culture. Addition of fetal calf serum to cultures cau sed a rapid and irreversible down-regulation of the RLF gene. Also, LH caus ed a decline in specific gene expression in longterm primary theca cell cul tures. As in the Leydig cells of the testis, the pattern of RLF gene expres sion appears to reflect the differentiation state of the ovarian theca-lute al cell lineage, and should prove useful for mapping the fate of these cell s under differing stimulation regimes.