An androgen receptor mRNA isoform associated with hormone-induced cell proliferation

Abstract

The larynx of male Xenopus laevis undergoes an androgen-driven developmental transformation that enables the adult to produce his complex mate attraction song. During the early postmetamorphic period, androgen directs proliferation and differentiation of laryngeal muscle and cartilage. To explore the cellular and molecular basis of androgen control, we have cloned an androgen receptor cDNA from juvenile larynx. Here we identify two androgen receptor mRNA isoforms, α and β, differing within the A/B, or hypervariable, domain. Northern blot analyses reveal that the β isoform is transiently expressed during early juvenile stages, whereas the a transcript is expressed throughout postmetamorphic life. Using in situ hybridization and [3H]thymidine autoradiography, we examined the expression of androgen receptor mRNA isoforms during androgen-evoked cell proliferation and differentiation. The α and β transcripts are coexpressed in proliferating tissues of the juvenile larynx; in postmitotic differentiated tissues, only the a transcript is expressed. Because androgen receptor β mRNA is specifically expressed during hormone-evoked cell proliferation, we propose that this developmentally regulated mRNA isoform is required for the masculine program of cell addition within the developing vocal organ.