Presenilin-1 protein specifically expressed in Leydig cells with its expression level increased during rat testis development

The intramembrane protease SPPL2c promotes male germ cell development by cleaving phospholamban

Signal peptide peptidase (SPP) and the four homologous SPP-like (SPPL) proteases constitute a family of intramembrane aspartyl proteases with selectivity for type II-oriented transmembrane segments. Here, we analyse the physiological function of the orphan protease SPPL2c, previously considered to represent a non-expressed pseudogene. We demonstrate proteolytic activity of SPPL2c towards selected tail-anchored proteins. Despite shared ER localisation, SPPL2c and SPP exhibit distinct, though partially overlapping substrate spectra and inhibitory profiles, and are organised in different high molecular weight complexes. Interestingly, SPPL2c is specifically expressed in murine and human testis where it is primarily localised in spermatids. In mice, SPPL2c deficiency leads to a partial loss of elongated spermatids and reduced motility of mature spermatozoa, but preserved fertility. However, matings of male and female SPPL2c-/- mice exhibit reduced litter sizes. Using proteomics we identify the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA2)-regulating protein phospholamban (PLN) as a physiological SPPL2c substrate. Accumulation of PLN correlates with a decrease in intracellular Ca2+ levels in elongated spermatids that likely contribute to the compromised male germ cell differentiation and function of SPPL2c-/- mice.

Leydig cells of the human testis possess astrocyte and oligodendrocyte marker molecules

It has been established, that Leydig cells of the human testis possess neuroendocrine properties and are therefore a member of the diffuse neuroendocrine (paraneuron) system. In the present study, we examined whether Leydig cells of adult (51-86 year of age) and developing (between the 15th and 36th week of gestation) human testes are immunopositive for glial cell-specific antigens such as glial fibrillary acidic protein (GFAP), galactocerebroside (GalC), cyclic 2',3'-nucleotide-3'-phosphodiesterase (CNPase), A2B5-antigen (A2B5) and O4-antigen (O4). With the use of Western blots and dot blot analyses, respectively, GFAP, CNPase, GalC, A2B5 and O4 were found in whole testes and Leydig cell protein extracts of adult men. Corresponding immunohistochemical studies revealed presence of these antigens in the cytoplasm of Leydig cells both of adult testes and testes during prenatal development. Some differences in staining intensity of single antigens were observed probably depending on the functional and/or developmental stage of the single cells. In addition, GFAP-, GalC- and CNPase-immunopositivity was found in numerous Sertoli cells of the seminiferous tubules. Moreover, some connective tissue cells (compartmentalizing cells or Co-cells) of the intertubular space showed immunopositivity for CNPase, A2B5 and GalC. The results obtained show that Leydig cells of the human testis, in addition to their endocrine, neuronal and neuroendocrine features, possess qualities of both astrocytes and oligodendrocytes and thus show qualities of multipotential cells. Leydig cells probably differentiate to a phenotype that is characteristic for cells in the developing nervous system. Furthermore, the established immunohistochemical similarities are consistent with the assumption that foetal and postnatal Leydig cells are of common origin.

Expression of Notch pathway components in spermatogonia and Sertoli cells of neonatal mice

Members of the Notch gene family have been shown to play an important role in the control of cell fate in many developmental systems. We hypothesized that the fate of the male germ line stem cells may also be mediated through the Notch signaling pathway. We therefore sought to determine whether the components of the Notch pathway are expressed in the mouse testis. Western blot analysis revealed the expression of three Notch receptors (Notch 1, Notch 2, and Notch 3), Notch ligands (Jagged 1, Jagged 2, and Delta 1), and presenilin 1 (PS1) in neonatal mouse testis. We then examined their cellular localization by immunohistochemical analysis of cocultures of spermatogonia and Sertoli cells. The 3 Notch receptors were found to be expressed in spermatogonia. Sertoli cells expressed only Notch 2 receptor. Among the Notch ligands, Delta 1 and Jagged 1 were localized exclusively in spermatogonia and Sertoli cells, respectively. PS1 was apparent in both spermatogonia and Sertoli cells. The presence of Notch receptors and Notch ligands in spermatogonia and Sertoli cells indicates that these cells are capable of responding to and eliciting Notch signaling during the process of spermatogenesis. Key words: Cell fate, delta, jagged, presenilin, spermatogenesis.