Ontogeny of LH receptor gene expression in the pig reproductive tract

In view of the recently documented expression of the LH receptor gene in several nongonadal reproductive tissues, the aim of this study was to analyse further the ontogeny of expression of this gene in the pig reproductive tract in fetal and neonatal life. RT-PCR was used to investigate the expression of the extracellular and transmembrane receptor domains, and to identify the time of onset of transcription of the full-length LH receptor mRNA and its shorter splice variants. Expression of the LH receptor gene was first detected around day 30 of fetal life in both ovary and testis, coinciding with morphological differentiation. The pattern of expression of LH receptor splice variants did not change during postnatal gonadal maturation. Expression of the LH receptor gene in the pig non-gonadal reproductive tract started during fetal life and continued during sexual maturation. A novel pig LH receptor spliced variant, lacking exon 10, was detected for the first time. The transmembrane receptor domain was expressed in fetal tissues, but not in neonatal control tissues. On the basis of the transmembrane domain of the LH receptor mRNA, it is concluded that the ovary and extragonadal tissues of the pig reproductive tract, like the pig testis, synthesize functional LH receptors during fetal life. The presence of LH receptor mRNA in extragonadal reproductive tissues indicates that LH is involved in the control and regulation of reproductive tract maturation.