Multiple levels of regulation exist for expression of the Hoxa-4 (Hox-1.4) gene in the mouse testis

Abstract

The experiments presented in this study show that the testis-specific expression of the murine Hoxa-4 (formerly Hox-1.4) gene is likely to be achieved through a variety of regulatory mechanisms operating on several levels. S1 mapping analysis suggested the possibility of multiple testicular transcripts arising from alternative splicing events. Analysis of cDNA and genomic sequences revealed the presence of two polyadenylation signals: the canonical AATAAA and further 3', an ATTAAA. Primer extension analysis to determine the start site of the testicular transcripts and nuclear run-on analysis suggested the use of a more upstream promoter than the one previously identified. The nuclear run-on analysis further suggested that Hoxa-4 is under posttranscriptional control. RNase H analysis showed that the size difference between the two testicular Hoxa-4 transcripts of 1.35 and 1.45 kb was due to a postmeiotic increase in poly(A) tail length. Only a proportion of the Hoxa-4 mRNA in germ cells was found to be associated with polysomes, suggesting that translational regulation may also operate as a means of control of Hoxa-4 expression in this adult lineage.