Male germ cell apoptosis: regulation and biology

Abstract

Cellular apoptosis appears to be a constant feature in the adult testis and during early development. This is essential because mammalian spermatogenesis is a complex process that requires precise homeostasis of different cell types. This review discusses the latest information available on male germ cell apoptosis induced by hormones, toxins and temperature in the context of the type of apoptotic pathway either the intrinsic or the extrinsic that may be used under a variety of stimuli. The review also discusses the importance of mechanisms pertaining to cellular apoptosis during testicular development, which is independent of exogenous stimuli. Since instances of germ cell carcinoma have increased over the past few decades, the current status of research on apoptotic pathways in teratocarcinoma cells is included. One other important aspect that is covered in this review is microRNA-mediated control of germ cell apoptosis, a field of research that is going to see intense activity in near future. Since knockout models of various kinds have been used to study many aspects of germ cell development, a comprehensive summary of literature on knockout mice used in reproduction studies is also provided.

Figure 1.

The apoptotic pathways. Cartoon showing primary apoptotic pathways.

Figure 2.

The pro- and anti-apoptotic molecules. Schematic diagram indicates points at which apoptosis occurs during spermatogenesis, the pro- and anti-apoptotic molecules involved and function of the apoptotic process related to the stages of sperm differentiation and maturation.

Figure 3.

Model of chromatoid body mediated translational repression and apoptosis in postmeiotic male germ cells. In postmeiotic germ cells, the haploid gene transcripts in the nuclei are assembled into ribonucleoprotein particles and exported to the cytoplasm to be stored into the perinuclear chromatoid bodies. The schematic diagram shows events related to apoptosis in postmeiotic germ cells.