Localization and quantitative expression of mRNAs encoding the testis-specific histone TH2B, the phosphoprotein p19, the transition proteins 1 and 2 during pubertal development and throughout the spermatogenic cycle of the rat.

Expression of the testis-specific histone TH2B, the phosphoprotein p19, and the transition proteins TP1 and TP2, was localized in the rat testis and quantified, using in situ hybridization of their mRNAs with radiolabeled probes and image analysis. In a first study, expression was assessed during testicular development between day 2 and day 65 postpartum. TH2B mRNAs appeared first in preleptotene spermatocytes (PL) on day 12 and in pachytene spermatocytes (PS) on day 18; p19 mRNAs were present in PS from day 18 onward, and TP1 and TP2 mRNAs were detected in round spermatids (RS) from day 32 onward. In the second trial, the expression of these four genes was studied throughout the cycle of spermatogenic epithelium in mature animals. TH2B mRNAs were localized in B spermatogonia at stage V, and in PL at stages VII and VIII but no longer in leptotene and zygotene spermatocytes. Thereafter, TH2B mRNAs were observed in PS from stages III-IV to XIII. The steady-state mRNA level per cell was high in PS with a maximum at stages IX-X. p19 mRNAs were present in PS from stages III-IV onward and in RS up to stages 1-2 of spermiogenesis. The maximum mRNA level per cell was observed in PS between stages VII and XIII. The presence of TP1 mRNAs was restricted to spermatids from steps 6 to 15-16 of spermiogenesis while TP2 mRNAs were detected in spermatids only between step 7 and step 13. The highest steady-state amounts of mRNAs were observed between step 7 and step 14 for TP1 and between step 10 and step 12 for TP2.