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Unique adenosine 3',5' cyclic monophosphate phosphodiesterase messenger ribonucleic acids in rat spermatogenic cells:
J E Welch1, J V Swinnen, D A O'Brien
1Gamete Biology Section, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709.
Abstract:
Four cAMP phosphodiesterase (cAMP-PDE) genes (ratPDE1, ratPDE2, ratPDE3, and ratPDE4) are expressed in the rat testis (Swinnen et al., PNAS USA 1989; 86:5325). Since multiple ratPDE1 and ratPDE2 mRNAs were present in male germ cells, their developmental expression was investigated by using purified spermatogenic cell populations. RatPDE1 mRNAs (4.0 and 2.8 kb) were found to be abundant in pachytene spermatocytes. RatPDE1 mRNA levels were decreased in round spermatids and absent from condensing spermatids/residual bodies. However, multiple ratPDE2 mRNAs (4.0, 3.5, 3.1, 2.8, and 2.4 kb) were abundant in round spermatids, and lower amounts were present in condensing spermatids/residual bodies. Transcripts related to ratPDE2 were also present in mouse round spermatids. Chromatography of germ cell cytosol identified two peaks of cAMP-PDE activity. Whereas peak A was evident in all germ cell populations examined, peak B was present in pachytene spermatocytes and round spermatids, but was at the limit of detection in condensing spermatids/residual bodies. The large decrease in peak B activity in condensing spermatids/residual bodies may be related to the drop in ratPDE1 mRNA levels observed during spermatogenesis. The sustained peak A activity in condensing spermatids/residual bodies coincides with the presence of ratPDE2 mRNA in these cells and suggests that the ratPDE2 enzyme may function during spermiogenesis and in spermatozoa.
Insights
This study investigates cyclic adenosine monophosphate phosphodiesterase (cAMP-PDE) gene expression during rat sperm development. RatPDE2 mRNA and cAMP-PDE activity peak in round spermatids, suggesting a role in spermiogenesis.
Area of Science:
- Reproductive Biology
- Molecular Endocrinology
- Spermatogenesis
Background:
- Four cyclic adenosine monophosphate phosphodiesterase (cAMP-PDE) genes are expressed in rat testes.
- Multiple ratPDE1 and ratPDE2 messenger RNAs (mRNAs) are found in male germ cells.
Purpose of the Study:
- To investigate the developmental expression of ratPDE1 and ratPDE2 mRNAs in purified spermatogenic cell populations.
- To correlate cAMP-PDE activity with specific germ cell types during spermatogenesis.
Main Methods:
- Purification of rat spermatogenic cell populations.
- Analysis of ratPDE1 and ratPDE2 mRNA expression using Northern blotting.
- Chromatographic separation of cAMP-PDE activity in germ cell cytosol.
Main Results:
- RatPDE1 mRNAs were abundant in pachytene spermatocytes but decreased in later stages.
- Multiple ratPDE2 mRNAs were abundant in round spermatids and present in condensing spermatids.
- Two peaks of cAMP-PDE activity were identified; peak A was sustained, while peak B decreased in later stages.
Conclusions:
- RatPDE1 mRNA levels decrease as spermatogenesis progresses.
- Sustained cAMP-PDE activity (peak A) in late spermatids and spermatozoa suggests a role for the ratPDE2 enzyme during spermiogenesis and in mature sperm.
- The findings provide insights into the molecular regulation of cAMP signaling during male gamete formation.