Expression of Estrogen Receptor ESR1 and Its 46-kDa Variant in the Gubernaculum Testis1

Abstract

Testicular descent corresponds to migration of the testis from the abdominal cavity to the scrotum and is essential for proper functioning of the testis. Recent advances in the characterization of estrogen receptor (ESR) subtypes and isoforms in various tissues prompted us to study ESRs within the gubernaculum testis, a structure involved in testicular descent. In the rat gubernaculum, we searched for ESR alpha (Esr1) and beta (Esr2) and for the androgen receptor (Ar), androgens being known to regulate testicular descent. Reverse transcription-polymerase chain reaction (RT-PCR) revealed that Esr1, Esr2, and Ar mRNAs were all expressed in the gubernaculum. Using PEETA (Primer extension, Electrophoresis, Elution, Tailing, and Amplification), we established that all Esr1 leader exons, previously identified in other organs, such as the uterus and pituitary, were transcribed in the gubernaculum, with the major form being O/B. The RNA protection assays, RT-PCR, and Western blot experiments revealed that isoform-specific mRNA transcripts generated by alternative splicing of the C-leader sequence on coding exons 1 and 2 of the Esr1 gene gave the 46- and 66-kDa ESR1 proteins. The ESR1 and AR proteins were found to colocalize in the parenchymal cells of the gubernaculum early in development, whereas AR also was strongly expressed in the muscular cells, both during fetal and postnatal life. The ESR2 protein was weakly expressed, principally in the muscular cells, but only once testicular descent had occurred. The levels of the 46-kDa ESR1 variant (ER46) exceeded those of the 66-kDa ESR1 form (ER66) at periods when the gubernaculum developed. Conversely, the 66-kDa form appears to predominate clearly when the gubernaculum growth was low or completed. The possible role of estrogens on the modulation of the androgen-dependent growth of the gubernaculum and, more widely, on testicular descent is discussed.