POSTNATAL CHANGES IN THE CALCIUM BINDING PROTEINS OF MOUSE TESTIS

Protein expression pattern of calcium-responsive transactivator in early postnatal and adult testes

Calcium-responsive transactivator (CREST), a nuclear protein highly expressed in postmitotic neurons, is involved in the regulation of cell cycle, differentiation and dendritic development of neuronal cells. Its mRNA has been detected in the testis of adult rat, whilst its protein expression and distribution pattern in the testis remain to be elucidated. In this study, we examined the distribution of CREST in the adult testes of both rats and human as well as the expression pattern of CREST in the testes of postnatal developing rats. In the adult testes of both human and rats, immunohistochemical analysis revealed that CREST was selectively distributed in the mature Sertoli cells but not in the spermatogenic cells. In the testes of postnatal developmental rats, CREST was expressed not only in Sertoli cells but also in the gonocytes and spermatogenic cells at the initial stage of spermatogenic cell differentiation. CREST immunoreactivity continued to increase in Sertoli cells during differentiation, reaching its peak in adulthood. However, CREST immunostaining intensity dramatically decreased as the spermatogenic cells differentiate, disappearing in the post-differentiation stage. Furthermore, Brg1 and p300, two CREST-interacting proteins ubiquitously expressed in the body, are found to be colocalized with CREST in the spermatogenic epithelial cells including Sertoli cells. The unique expression pattern of CREST in developing testis suggests that CREST might play regulatory roles in the differentiation of spermatogenic epithelial cells. The Sertoli cell-specific expression of CREST in the adulthood hints that CREST might be a novel biomarker for the mature Sertoli cells.

Effects of calcium channel blockers on the spermatogenesis and gene expression in peripubertal mouse testis

Treatment of Ca(2+) channel blockers (CCB) to relieve hypertension causes reversible male infertility, suggesting deregulation of Ca(2+) homeostasis in testis is closely related with male infertility. To investigate the possible toxicity of therapeutic application of CCB in childhood, the effect of nifedipine and ethosuximide, an L-type and T-type CCB, respectively, on the spermatogenesis and testicular gene expression was examined. Following the intraperitoneal injection of either drug for 7 days to 18 days on old mice, the paired testes weights were significantly lower in mice treated with nifedipine (> or = 10 mg/kg/day) or ethosuximide (100 mg/kg/day) than vehicle controls. In mice given high drug dosing (100 mg/kg), seminiferous tubules showed immaturity with spermatogenic arrest at elongating spermatid stage and poorly developed lumen. Unexpectedly, the expression of activator isoform of transcription factor cAMP-responsive element modulator (CREM) mRNA increased together with transition protein 2 and protamine 2 mRNA in drug-treated mice testes, suggesting that CCB may deregulate expression of activator isoform of CREM in male germ cells and that spermatogenic defect following CCB treatment may attribute to ectopic expression of CREM-dependent gene battery in testis. Therapeutic application of CCB in childhood should be cautious because of their potential to cause spermatogenic defect and altered gene expression in testis.