Proteomic profiling of epididymis and vas deferens: identification of proteins regulated during rat genital tract development

A proteomic comparison of immature and mature mouse gonadotrophs reveals novel differentially expressed nuclear proteins that regulate gonadotropin gene transcription and RNA splicing

The alphaT3-1 and LbetaT2 gonadotroph cell lines contain all the known factors required for expression of gonadotropin genes, yet only the LbetaT2 cells express the beta subunits. We hypothesized that comparison of their nuclear proteomes would reveal novel proteins and/or modifications that regulate expression of these genes. We identified nine proteins with different expression profiles in the two cell lines, of which several were chosen for further functional studies. Of those found at higher levels in alphaT3-1 nuclei, 1110005A23RIK was found associated with the Fshb gene promoter and repressed its expression. Transgelin 3 overexpression reduced transcript levels of Fshb, and its knockdown elevated Lhb and Cga transcript levels, indicating an ongoing repressive effect on these more highly expressed genes, possibly through altering levels of phosphorylated mitogen-activated protein kinase. Heterogeneous nuclear ribonucleoprotein A2/B1 repressed splicing of the Fshb primary transcript, which it binds in the first intron. Proteins at higher levels in LbetaT2 nuclei included prohibitin, the overexpression of which reduced promoter activity of all three gonadotropin subunits, and appeared to mediate the differential effect of GnRH on proliferation of the two cell lines; its knockdown also altered cell morphology. Two other splicing factors were also found at higher levels in LbetaT2 nuclei: the knockdown of PRPF19 or EIF4A3 decreased splicing of Lhb, or of both beta subunit transcripts, respectively. The levels of Eif4a3 mRNA were increased by activin, and both factors increased Fshb splicing. This study has revealed a number of novel factors that alter gonadotropin expression and gonadotroph function, and likely mediate or moderate effects of the regulatory hormones.

Bfk, a novel member of the bcl2 gene family, is highly expressed in principal cells of the mouse epididymis and demonstrates a predominant nuclear localization

B-cell lymphoma 2 (BCL2) family kin (BFK) is a recently identified novel protein that is similar to proteins of the BCL2 family. In the present study, we discovered that the mouse Bfk transcript is expressed at the highest level in the epididymis. Two transcripts of 0.9 and 2.6 kb in size were identified, with alternative exon 4 structures, resulting in a difference in the last three to five amino acids of the variants. However, the 0.9-kb transcript was found to be the predominant form in the epididymis and mammary gland, another tissue with strong Bfk expression. Epididymal Bfk expression was regulated both by androgens and other testicular factors. It is thus one of the few initial-segment enriched genes under androgen control, the majority of them being regulated by other testicular factors. BFK protein was expressed specifically in the principal cells of the epididymis. Its nuclear localization was evident in the initial segment and caput epididymis and in the epithelium of pregnant female mammary gland. The expression of BFK-enhanced green fluorescent protein recombinant protein in epididymal cells further confirmed the predominant nuclear localization of BFK with nucleo-cytoplasmic shuttling. Overexpressing BFK in epididymal cells did not induce apoptosis. However, enhanced caspase 3 activation was observed in the presence of BFK upon staurosporine-induced apoptosis. This suggests that BFK may have a proapoptotic role only after the process has been initiated by other mechanisms. Being exceptionally highly expressed in the initial segment, Bfk is suggested to have a role in the differentiation of this segment of the epididymis.

Comparison Between Epididymosomes Collected in the Intraluminal Compartment of the Bovine Caput and Cauda Epididymidis1

During their transit along the epididymidis, mammalian spermatozoa acquire new proteins involved in the acquisition of male gamete fertilizing ability. We previously described membranous vesicles called epididymosomes, which are secreted in an apocrine manner by the epididymal epithelium. Some selected proteins associated with epididymosomes are transferred to spermatozoa during epididymal transit. The present study compared epididymosomes collected from caput epididymal fluid with vesicles from the cauda epididymidis in the bull. Two-dimensional gel electrophoresis revealed major differences in protein composition of epididymosomes isolated from the caput and cauda epididymidis. LC-QToF analysis of major protein spots as well as Western blot analysis confirmed the differences in proteins associated with these two populations of epididymosomes. Biotinylated proteins associated with caput and cauda epididymosomes also revealed differences. When incubated with caput epididymal spermatozoa, epididymosomes prepared from these two segments transferred different protein patterns. By contrast, cauda epididymosomes transferred the same pattern of proteins to spermatozoa from the caput and cauda epididymidis. Transfer of biotinylated proteins from cauda epididymosomes to caput spermatozoa decreased in a dose-dependent manner when biotinylated epididymosomes were diluted with unbiotinylated vesicles. Caput epididymosomes added in excess were unable to inhibit transfer of biotinylated proteins from cauda epididymosomes to caput spermatozoa. Following transfer of biotinylated proteins from cauda epididymosomes to caput spermatozoa, addition of unbiotinylated cauda epididymosomes was unable to displace already transferred biotinylated proteins. These results established that epididymosomes from caput and cauda epididymidis have different protein composition and interact differently with maturing spermatozoa.

Changes in Gene Expression during Wolffian Duct Development

BACKGROUND

Wolffian ducts (WDs) are the embryonic precursors of the male reproductive tract. Their development is induced by testosterone, which interacts with the androgen receptor (AR). The molecular pathways underlying androgen-dependent WD development are largely unknown. We aimed to identify AR target genes important in this process.

METHODS

RNA was isolated from rat WDs at E17.5 and E20.5. Affymetrix GeneChip expression arrays were used to identify transcripts up- or downregulated more than 2-fold. Regulation of seven transcripts was confirmed using quantitative PCR.

RESULTS

Transcripts from 76 known genes were regulated, including modulators of insulin-like growth factor and transforming growth factor-beta signalling. By controlling these modulators, androgens may indirectly affect growth factor signalling pathways important in epithelial-mesenchymal interactions and organ development. Caveolin-1, also upregulated, may play a role in modifying as well as mediating AR signalling. Differentiation of WD epithelium and smooth muscle, innervation and extracellular matrix synthesis were reflected in regulation of other transcripts. Several genes were previously suggested to be regulated by androgens or contained functional or putative androgen/glucocorticoid response elements, indicating they may be direct targets of androgen signalling.

CONCLUSION

Our results suggest novel cohorts of signals that may contribute to androgen-dependent WD development and provide hypotheses that can be tested by future studies.

Comparative proteomic analysis to study molecular events during gonad development in mice

Sex determination represents a critical bifurcation in the road of embryonic development. It is based on a finely regulated network of gene activity, as well as protein-protein interactions and activation or silencing of signaling pathways. Despite the identification of a number of critical genes, many aspects of the molecular cascade that drives the differentiation of the embryonic gonad into either a testis or an ovary remain poorly understood. To identify new proteins involved in this cascade, we employed two-dimensional gel electrophoresis and mass spectrometry to compare the protein expression profiles of fetal mouse testes and ovaries. Three proteins, hnRPA1, TRA1, and HSC71, were found to be expressed in a male-specific manner and this expression was confirmed by real-time reverse transcriptase polymerase chain reaction (RT-PCR) and in situ hybridization. Moreover, HSC71 was found to be hyperphosphorylated in male compared to female gonads, emphasizing the advantage of the proteomic approach in allowing the detection of posttranslational modifications.