Male sterility in mice lacking retinoic acid receptor α involves specific abnormalities in spermiogenesis

Abstract

The severe degeneration of the germinal epithelium and subsequent male sterility observed in mice null for the retinoic acid receptor (RAR ) gene suggested its critical role in spermatogenesis, although the etiology and progression of these abnormalities remain to be determined. Previous studies have revealed that elongated spermatids in RAR −/− testes were improperly aligned at the tubular lumen and did not undergo spermiation at stage VIII*. We now report a distinctive failure of step 8-9 spermatids to orient properly with regard to the basal aspect of Sertoli cells, resulting in stage VIII*-IX* tubules with randomly oriented spermatids. By in situ terminal deoxynucleo-tidyltransferase-mediated deoxy-UTP nick end labeling (TUNEL), we noted that elongating spermatids frequently underwent apoptosis. Immunohistochemical analysis revealed that while activated caspase-3, the primary effector caspase in the apoptotic cell death machinery, was detected in the nuclei of primary spermatocytes in the first wave of spermatogenesis and occasionally in spermatogonia of both normal and mutant testes, it was not involved in the death of elongating spermatids in RAR −/− testes. Thus, sterility in RAR −/− males was associated with specific defects in spermiogenesis, which may correlate with a failure in both spermatid release and spermatid orientation to the basal aspect of Sertoli cells at stage VIII* in young adult RAR −/− testis. Further, the resulting apoptosis in elongating spermatids appears to involve pathways other than that mediated by activated caspase-3.

Retinoids and spermatogenesis: Lessons from mutant mice lacking the plasma retinol binding protein

“…During the progression of VAD, this defect precedes the onset of testis degeneration. Of interest, a similar spermiation failure has been observed in rats under VAD conditions (Huang and Marshall, 1983;Huang et al, 1988), as well as in Rara-or Rxrb-null mutant mice (Lufkin et al, 1993;Kastner et al, 1996;Mascrez et al, 2004;Chung et al, 2005). Altogether, these data suggest that spermiation requires RA-liganded RAR␣/RXR␤ heterodimers in the seminiferous epithelium.…”

“…Similar observations were made from vitamin A-deficient rat testes (Ismail et al, 1990;van Pelt et al, 1995). In addition, acute and massive death of spermatocytes and round spermatids accompanies testicular degeneration in vitamin A-deficient rats de Rooij et al, 1994), whereas apoptosis is of these cells is markedly increased of Rara-null mutant mice (Chung et al, 2005). Thus, either ROL-or RA-signalling pathways seem to be required for the survival of all types of germ cells in rodents.…”

“…Rara is expressed mainly, if not exclusively, in Sertoli cells (Vernet et al, 2006), and spermatogenesis is dramatically disturbed in Rara-null mutants. Both VAD mice (present report) and Raranull mutants (Lufkin et al, 1993;Chung et al, 2005) display a failure of spermatid release, a degradation of elongated spermatids by Sertoli cells and a chronic desquamation of immature germ cells, thus indicating that the effects of RA on spermiation and on germ cell adhesion to Sertoli cells are mediated by RAR␣. However, Rara-null testes do not show histological features indicative of a delay in spermatogonia differentiation that is most remarkable hallmark of VAD-induced testis degeneration (present report).…”

“…Second, the outcome of VAD in the seminiferous epithelium differs between these species: in VAD rats, spermatogenesis is arrested at the preleptotene spermatocyte stage (Huang and Humbree, 1979;Huang et al, 1990;Ismail et al, 1990), whereas in VAD mice, it is arrested at the spermatogonia stage (Huang and Hembree, 1979;Gaemers et al, 1997). Third, the functions of retinoid receptors in vivo are documented from the analysis of genetically altered mouse models (Lufkin et al, 1993;Kastner et al, 1996;Mascrez et al, 2004;Chung et al, 2005;Liu and Gudas, 2005) but not from rat models.…”

Differentiation of spermatogonial stem cell-like cells from murine testicular tissue into haploid male germ cells in vitro

“…RA is a retinoids which can alter gene expression in testis (ClagettDame and DeLuca 2002), heart (Das et al 2007), central nervous system (Kastner et al 1995) craniofacial structures, limbs, brain, and eyes (Clagett-Dame and DeLuca 2002; Das et al 2007;Kastner et al 1995;Ross et al 2000;Wolgemuth and Chung 2004;Zile 1998). Chung et al (2005) reported that the lack of retinoic acid receptor a could lead to male sterility in mice as well as specific abnormalities in spermiogenesis (Chung et al 2005). It has been proven that foetal cattle mGCs (male germ cells) were induced by RA to generate some elongated sperm-like cells (Dong et al 2010).…”