Elongated Spermatids Research Articles

Phosphatidylinositol 4-Phosphate 5-Kinase Is Indispensable for Mouse Spermatogenesis1

The lipid kinase phosphatidylinositol 4-phosphate 5-kinase (PIP5K) produces a versatile signaling phospholipid, phosphatidylinositol 4,5-bisphosphate. Three PIP5K isozymes, PIP5K1A, PIP5K1B, and PIP5K1C, have been identified in mammals so far. Although the functions of these three PIP5K isozymes have been extensively studied in vitro, the in vivo physiological roles of these PIP5K isozymes remain largely unknown. In this study, we examined the functions of PIP5K1A and PIP5K1B in spermatogenesis, using Pip5k1a-knockout (KO), Pip5k1b-KO, and Pip5k1a/Pip5k1b double (D)-KO mice. Pip5k1a-KO and D-KO males were subfertile and completely sterile, respectively. F-actin in the seminiferous epithelium was disorganized in the D-KO mice, although F-actin bundles at the apical ectoplasmic specialization was not affected. D-KO seminiferous tubules contained a greatly decreased number of elongated spermatids. Flagella of sperm from Pip5k1a-KO and D-KO mice remarkably underwent morphological change, whereas Pip5k1b-KO sperm were morphologically normal. Notably, the flagellar shape of D-KO sperm was more severely impaired than that of Pip5k1a-KO sperm. These results suggest that PIP5K1A and PIP5K1B may coordinately and/or redundantly function in the maintenance of sperm number and morphology during spermatogenesis.

Nemo-like kinase promotes etoposide-induced apoptosis of male germ cell-derived GC-1 cells in vitro

Spermatogenesis is an extremely intricate process that is tightly regulated and orchestrated by a series of well-coordinated gene expression programmes. Nemo-like kinase (NLK) is an evolutionarily conserved serine/threonine kinase that functions in a wide variety of developmental events. Nevertheless, the function of NLK in spermatogenesis has not been investigated. In this study, we found that the distribution of NLK in mice exhibited a dynamic change during testicular development and gradually became concentrated in the acrosomes of elongated spermatids. NLK overexpression promoted etoposide-induced apoptosis of male germ cell-derived GC-1 cells, while knockdown of NLK by RNA interference (RNAi) attenuated etoposide-induced apoptosis. Our findings suggest that NLK plays an important role in etoposide-induced germ cell apoptosis and may be associated with spermatogenesis.

Regulation of exclusively testis‐expressed microRNA‐469 by Gonadotropin‐Regulated Testicular RNA Helicase controls male germ cells development

Gonadotropin‐regulated testicular RNA helicase (GRTH/DDX25), a testis‐specific member of the DEAD‐box family, is an essential post‐transcriptional regulator of spermatogenesis. Failure of expression of Transition protein 2 (TP2) and Protamine 2 (Prm2) proteins (chromatin remodelers, essential for spermatid elongation and completion of spermatogenesis) with preservation of their mRNAs expression was observed in GRTH−/− mice (azoospermic due to failure of spermatids to elongate). These were identified as target genes for the testis‐specific miR‐469, which is increased in the GRTH−/− mice. Further analysis demonstrated that miR‐469 repressed TP2 and Prm2 protein expression at the translation level with minor effect on mRNA degradation, through binding to the coding regions of TP2 and Prm2 mRNAs. The corresponding primary‐miRNAs and the expression levels of Drosha and DGCR8 (mRNA and protein) were increased significantly in the GRTH−/− mice. miR‐469 silencing of TP2 and Prm2 mRNA in pachytene spermatocytes and round spermatids is essential for their timely translation at later times of spermiogenesis which is critical to attain mature sperm. Collectively, these studies indicate that GRTH, a multifunctional RNA helicase, acts as a negative regulator of miRNA biogenesis and consequently their function during spermatogenesis. (Supported by the IRP, NICHD)

The Testicular and Epididymal Expression Profile of PLCζ in Mouse and Human Does Not Support Its Role as a Sperm-Borne Oocyte Activating Factor

Phospholipase C zeta (PLCζ) is a candidate sperm-borne oocyte activating factor (SOAF) which has recently received attention as a potential biomarker of human male infertility. However, important SOAF attributes of PLCζ, including its developmental expression in mammalian spermiogenesis, its compartmentalization in sperm head perinuclear theca (PT) and its release into the ooplasm during fertilization have not been established and are addressed in this investigation. Different detergent extractions of sperm and head/tail fractions were compared for the presence of PLCζ by immunoblotting. In both human and mouse, the active isoform of PLCζ was detected in sperm fractions other than PT, where SOAF is expected to reside. Developmentally, PLCζ was incorporated as part of the acrosome during the Golgi phase of human and mouse spermiogenesis while diminishing gradually in the acrosome of elongated spermatids. Immunofluorescence localized PLCζ over the surface of the postacrosomal region of mouse and bull and head region of human spermatozoa leading us to examine its secretion in the epididymis. While previously thought to have strictly a testicular expression, PLCζ was found to be expressed and secreted by the epididymal epithelial cells explaining its presence on the sperm head surface. In vitro fertilization (IVF) revealed that PLCζ is no longer detectable after the acrosome reaction occurs on the surface of the zona pellucida and thus is not incorporated into the oocyte cytoplasm for activation. In summary, we show for the first time that PLCζ is compartmentalized as part of the acrosome early in human and mouse spermiogenesis and is secreted during sperm maturation in the epididymis. Most importantly, no evidence was found that PLCζ is incorporated into the detergent-resistant perinuclear theca fraction where SOAF resides.

Germ Cell Transplantation in Felids: A Potential Approach to Preserving Endangered Species

With the exception of the domestic cat, all members of the family Felidae are considered either endangered or threatened. Although not yet used for this purpose, spermatogonial stem cell (SSC) transplantation has a high potential to preserve the genetic stock of endangered species. However, this technique has not previously been established in felids. Therefore, we developed the necessary procedures to perform syngeneic and xenogeneic SSC transplants (eg, germ cell [GC] depletion in the recipient domestic cats, enrichment and labeling of donor cell suspension, and the transplantation method) in order to investigate the feasibility of the domestic cat as a recipient for the preservation and propagation of male germ plasm from wild felids. In comparison with busulfan treatment, local x-ray fractionated radiation was a more effective approach to depleting endogenous spermatogenesis. The results of both syngeneic and xenogeneic transplants revealed that SSCs were able to successfully colonize and differentiate in the recipient testis, generating elongated spermatids several weeks posttransplantation. Specifically, ocelot spermatozoa were observed in the cat epididymis 13 weeks following transplantation. As donor GCs from domestic cats and ocelots were able to develop and form mature GCs in the recipient environment seminiferous tubules, these findings indicate that the domestic cat is a suitable recipient for SSC transplantation. Moreover, as modern cats descended from a medium-size cat that existed approximately 10 to 11 million years ago, these results strongly suggest that the domestic cat could be potentially used as a recipient for generating and propagating the genome of wild felids.

PABP Interacting Protein 2A (PAIP2A) Regulates Specific Key Proteins During Spermiogenesis in the Mouse1

During spermiogenesis, expression of the specific proteins needed for proper differentiation of male germ cells is under translational control. We have shown that PAIP2A is a major translational regulator involved in the maturation of male germ cells and male fertility. To identify the proteins controlled by PAIP2A during spermiogenesis, we characterized the proteomic profiles of elongated spermatids from wild-type (WT) mice and mice that were Paip2a/Paip2b double-null mutants (DKO). Elongated spermatid populations were obtained and proteins were extracted and separated on gradient polyacrylamide gels. The gels were digested with trypsin and peptides were identified by mass spectrometry. We identified 632 proteins with at least two unique peptides and a confidence level of 95%. Only 209 proteins were consistently detected in WT or DKO replicates with more than five spectra. Twenty-nine proteins were differentially expressed with at least a 1.5-fold change; 10 and 19 proteins were down- and up-regulated, respectively, in DKO compared to WT mice. We confirmed the significantly different expression levels of three proteins, EIF4G1, AKAP4, and HK1, by Western blot analysis. We have characterized novel proteins that have their expression controlled by PAIP2A; of these, 50% are involved in flagellar structure and sperm motility. Although several proteins affected by abrogation of Paip2a have established roles in reproduction, the roles of many others remain to be determined.

Detection of the activator cAMP responsive element modulator (CREM) isoform ortholog proteins in porcine spermatids and sperm

It is necessary to obtain basic information on transcription factors expressed in the spermatids of livestock to determine mechanisms of defective spermiogenesis. In this study, we characterized the activator cAMP responsive element modulator (CREM) ortholog isoforms in porcine testicular germ cells and ejaculated sperm. At least two kinds of porcine activator CREM τ family ortholog mRNAs were more strongly expressed in the testis than in kidney or liver. The activator CREM isoform ortholog proteins were localized in nuclei of round spermatids and around nuclei of elongated spermatids. Furthermore, approximately 34% of ejaculated sperm had the activator CREM isoform ortholog proteins at their connecting piece. This is apparently the first report demonstrating the expression and localization of the activator CREM isoform ortholog proteins in spermatids and ejaculated sperm of a livestock species.

Compensatory Upregulation of Myelin Protein Zero-Like 2 Expression in Spermatogenic Cells in Cell Adhesion Molecule-1-Deficient Mice

The cell adhesion molecule-1 (Cadm1) is a member of the immunoglobulin superfamily. In the mouse testis, Cadm1 is expressed in the earlier spermatogenic cells up to early pachytene spermatocytes and also in elongated spermatids, but not in Sertoli cells. Cadm1-deficient mice have male infertility due to defective spermatogenesis, in which detachment of spermatids is prominent while spermatocytes appear intact. To elucidate the molecular mechanisms of the impaired spermatogenesis caused by Cadm1 deficiency, we performed DNA microarray analysis of global gene expression in the testis compared between Cadm1-deficient and wild-type mice. Out of the 25 genes upregulated in Cadm1-deficient mice, we took a special interest in myelin protein zero-like 2 (Mpzl2), another cell adhesion molecule of the immunoglobulin superfamily. The levels of Mpzl2 mRNA increased by 20-fold and those of Mpzl2 protein increased by 2-fold in the testis of Cadm1-deficient mice, as analyzed with quantitative PCR and western blotting, respectively. In situ hybridization and immunohistochemistry demonstrated that Mpzl2 mRNA and protein are localized in the earlier spermatogenic cells but not in elongated spermatids or Sertoli cells, in both wild-type and Cadm1-deficient mice. These results suggested that Mpzl2 can compensate for the deficiency of Cadm1 in the earlier spermatogenic cells.

Accumulated HSV1-TK Proteins Interfere with Spermatogenesis through a Disruption of the Integrity of Sertoli-Germ Cell Junctions

Transgenic rats show spermatid-specific ectopic expression of the reporter gene, herpes simplex virus type1 thymidine kinase (HSV1-TK), in the testes and have demonstrated male infertility. However, the disruption of spermatogenesis and the underlying molecular mechanisms in these transgenic animals have not been well clarified. In this study, light and electron microscopic observations were performed to characterize the morphological changes in the testes. To explore the molecular mechanisms of male infertility in the HSV1-TK transgenic rat, cDNA microarray and quantitative real-time PCR analyses were performed. The seminiferous tubules of 3-month-old transgenic rats showed morphological alterations including seminiferous epithelial sloughing, vacuolization, and degeneration of spermatogenic cells, suggesting a failure of Sertoli-germ cell interaction. Components of the epididymal lumen from transgenic rats included abnormal spermatozoa, degenerating round spermatids and abnormal elongated spermatids indicating an appearance of direct impairment of spermiogenesis. cDNA microarray and real-time PCRanalyses revealed significant changes (P<0.05) in the gene expression level in six genes, testin, versican, mamdc1, fgf7, ostf1 and cnot7. Among them, testin drew most of our attention, since the testin gene is a sensitive marker for disruption of Sertoli-germ cell adhesion. Thus, our results suggest that the accumulation of HSV1-TK in the spermatids not only directly interferes with spermiogenesis but also disrupts spermatogenesis through a disruption of Sertoli-germ cell adhesions. It is important to explore the testicular actions of the HSV1-TK protein in transgenic experimental models and thereby gain clues to find an appropriate treatment for HSV-infected patients exhibiting human male infertility, as has been recently observed.

Localization of BRUNOL2 in Rat Spermatogenic Cells as Revealed by Immunofluorescence and Immunoelectron Microscopic Techniques

Distribution and localization of a RNA-binding protein, BRUNOL2 in rat spermatogenic cells were studied by dot blotting of cell fractions, immunofluorescence (IF), and immunoelectron microscopy (IEM). BRUNOL2 distributed in nuclear (23%), mitochondrial (19%), microsomal (15%), and cytosol fractions (43%). BRUNOL2 was detected in all spermatogenic cells. In the cytoplasm and nucleoplasm of the spermatogonia, spermatocytes and spermatids, both diffuse and granular staining patterns were observed. Many cytoplasmic granules were stained also for DDX4 and DDX25. Large granules in the cytoplasm of elongated spermatids were stained for BRUNOL2 but not for the nuage proteins. IEM showed that gold signals for BRUNOL2 were concentrated in nuage components including loose aggregates of small particles, chromatoid body (CB), intermitochondrial cement (IMC), and satellite body (SB). In addition, many non-nuage structures such as ER-attached small granules, less dense material surrounding connecting piece of flagellum, reticulated body, mitochondria-associated granules (MAG), granulated body, ribosome aggregate, and manchette, were stained for BRUNOL2 with different staining intensities. In the nucleus, gold signals were concentrated in heterochromatin area and nucleolus. The results suggest that BRUNOL2 is one of the nuage proteins and also associated with the other non-nuage structures, suggesting multiple functions of this protein.

Mixed testicular atrophy related to atherosclerosis: first lessons from the ApoE−/−/ LDL receptor−/− double knockout mouse model

Age-related testicular changes are associated with declining spermatogenesis and testosterone levels. A relationship to atherosclerosis has never been investigated systematically. The ApoE(-/-)/LDL receptor(-/-) double knockout mouse model, providing a remarkable homology to human atherosclerosis, is an ideal tool to investigate spermatogenetic alterations in this context. Testes (n = 10) from ApoE(-/-)/LDL receptor(-/-) double knockout mice at the age of 80 weeks were perfused in vivo with contrast agent, harvested and scanned with micro-CT at (4.9 μm³) voxel size. Testes (n = 8) of C57/BL mice at the same age served as controls. Testis volume (mm³) and total vascular volume fraction (mm³) were quantified using micro-CT. Serum testosterone levels were determined. Testicular histology and epididymal sections were analysed for tubular structure, spermatogenetic scores and sperm count. The expression of protamine 2 as a marker for elongated spermatids, inflammation markers (CD4, F4/80) and hypoxia inducible factor 1 alpha (HIF1 alpha) were investigated using immunohistochemistry. ApoE(-/-)/LDL receptor(-/-) double knockout mice exhibit diminished testis and vascular volume fraction with respect to that of controls (p < 0.001). These findings were associated with a reduction of testosterone levels (p < 0.001). Mixed atrophy was present in 41% of the seminiferous tubuli in ApoE(-/-)/LDL receptor(-/-) double knockout mice at the age of 80 weeks. Sperm counts from the epididymis demonstrated a significant decrease in ApoE(-/-)/LDL receptor(-/-) double knockout mice (p < 0.001). In addition, sperm specific protamine 2 expression was decreased in testicular tissue and epididymis of ApoE(-/-)/LDL receptor(-/-) double knockout mice compared with that of control mice. Peritubular inflammatory infiltration and the expression of the hypoxia related marker was observed. Mixed testicular atrophy in ApoE(-/-)/LDL receptor(-/-) double knockout mice is linked to reduced testis volume, vascular volume fraction and low testosterone serum levels, suggesting a direct relation between atherosclerosis and disturbed spermatogenesis.

Abaxial tail implantation in the emu, Dromaius novaehollandiae: Morphological characteristics and origin of a rare avian sperm defect

Abaxial tail implantation is a defect occurring in the neck region of spermatozoa and is characterized by misalignment of the centriolar complex relative to the head base. This defect has been described in a number of mammalian species, but is rarely reported in birds. In this study, a detailed description of the defect in emu sperm is presented as well as morphological evidence of its origin in the testis. Despite their low incidence defective sperm could readily be identified using light (LM) and transmission electron microscopy (TEM). Affected sperm displayed obvious misalignment of the head and flagellum with many cells additionally showing unilateral swelling and caudal extension of the nuclear base. This material overlapped the anterior aspect of the centriolar complex. More subtle forms of the defect which were not resolved by LM were revealed by TEM. Abaxial sperm development could be identified in the testis during the early elongated spermatid stage of spermiogenesis. At this stage the centriolar complex was clearly misaligned with respect to the longitudinal axis of the condensing and elongating nucleus. The rare occurrence and low incidence of this defect in the emu would suggest that it has little effect on fertility.

Arylsulfatase A deficiency causes seminolipid accumulation and a lysosomal storage disorder in Sertoli cells

Sulfogalactosylglycerolipid (SGG) is the major sulfoglycolipid of male germ cells. During spermatogenesis, apoptosis occurs in >50% of total germ cells. Sertoli cells phagocytose these apoptotic germ cells and degrade their components using lysosomal enzymes. Here we demonstrated that SGG was a physiological substrate of Sertoli lysosomal arylsulfatase A (ARSA). SGG accumulated in Sertoli cells of Arsa(-/-) mice, and at 8 months of age, this buildup led to lysosomal swelling and other cellular abnormalities typical of a lysosomal storage disorder. This disorder likely compromised Sertoli cell functions, manifesting as impaired spermatogenesis and production of sperm with near-zero fertilizing ability in vitro. Fecundity of Arsa(-/-) males was thus reduced when they were older than 5 months. Sperm SGG is known for its roles in fertilization. Therefore, the minimal sperm fertilizing ability of 8-month-old Arsa(-/-) males may be explained by the 50% reduction of their sperm SGG levels, a result that was also observed in testicular germ cells. These unexpected decreases in SGG levels might be partly due to depletion of the backbone lipid palmitylpalmitoylglycerol that is generated from the SGG degradation pathway in Sertoli cells and normally recycled to new generations of primary spermatocytes for SGG synthesis.

Testis-specific miRNA-469 Up-regulated in Gonadotropin-regulated Testicular RNA Helicase (GRTH/DDX25)-null Mice Silences Transition Protein 2 and Protamine 2 Messages at Sites within Coding Region: IMPLICATIONS OF ITS ROLE IN GERM CELL DEVELOPMENT

Gonadotropin-regulated testicular RNA helicase (GRTH/DDX25), a testis-specific member of the DEAD-box family, is an essential post-transcriptional regulator of spermatogenesis. Failure of expression of Transition protein 2 (TP2) and Protamine 2 (Prm2) proteins (chromatin remodelers, essential for spermatid elongation and completion of spermatogenesis) with preservation of their mRNA expression was observed in GRTH-null mice (azoospermic due to failure of spermatids to elongate). These were identified as target genes for the testis-specific miR-469, which is increased in the GRTH-null mice. Further analysis demonstrated that miR-469 repressed TP2 and Prm2 protein expression at the translation level with minor effect on mRNA degradation, through binding to the coding regions of TP2 and Prm2 mRNAs. The corresponding primary-microRNAs and the expression levels of Drosha and DGCR8 (both mRNA and protein) were increased significantly in the GRTH-null mice. miR-469 silencing of TP2 and Prm2 mRNA in pachytene spermatocytes and round spermatids is essential for their timely translation at later times of spermiogenesis, which is critical to attain mature sperm. Collectively, these studies indicate that GRTH, a multifunctional RNA helicase, acts as a negative regulator of miRNA-469 biogenesis and consequently their function during spermatogenesis.

Gonadal status of male recipient mice influences germ cell development in immature buffalo testis tissue xenograft

Growth and development of immature testis xenograft from various domestic mammals has been shown in mouse recipients; however, buffalo testis xenografts have not been reported to date. In this study, small fragments of testis tissue from 8-week-old buffalo calves were implanted subcutaneously onto the back of immunodeficient male mouse recipients, which were either castrated or left intact (non-castrated). The xenografts were retrieved and analyzed 12 and 24 weeks later. The grafted tissue survived and grew in both types of recipient with a significant increase in weight and seminiferous tubule diameter. Recovery of grafts from intact recipients 24 weeks post-grafting was significantly lower than that from the castrated recipients. Seminal vesicle indices and serum testosterone levels were lower in castrated recipients at both collection time points in comparison to the intact recipients and non-grafted intact mouse controls. Pachytene spermatocytes were the most advanced germ cells observed in grafts recovered from castrated recipients 24 weeks post-grafting. Complete spermatogenesis, as indicated by the presence of elongated spermatids, was present only in grafts from intact recipients collected 24 weeks post-grafting. However, significant number of germ cells with DNA damage was also detected in these grafts as indicated by TUNEL assay. The complete germ cell differentiation in xenografts from intact recipients may be attributed to efficient Sertoli cell maturation. These results suggest that germ cell differentiation in buffalo testis xenograft can be completed by altering the recipient gonadal status.

Expression of BET genes in testis of men with different spermatogenic impairments

To characterize the BET gene expression in human testis with spermatogenetic impairments; to examine BRDT protein expression in testis and semen. Prospective study. Fertility clinic. Azoospermic men (n = 120) who underwent testicular sperm extraction and who were classified as either normal spermatogenesis, mixed atrophy, spermatocyte maturation arrest, or Sertoli cells only according to their combined histologic and cytologic testicular findings and three normozoospermic men who donated sperm. Evaluation of testicular biopsies by qualitative and quantitative reverse transcriptase-polymerase chain reaction, immunohistochemical staining, and analysis of spermatozoa by immunofluorescence. Expression of the four BET genes in testis and localization of BRDT protein in testicular tissue and ejaculated spermatozoa. The BRDT gene was not expressed in testicular tissue from patients with Sertoli cells only, whereas the other three genes of the BET family retained expression in all the pathologies. The BRDT protein was localized in the nuclei of spermatocytes, spermatids, and ejaculated spermatozoa. Expression of BRDT protein was almost nil in testicular tissue specimens with spermatocyte maturation arrest despite normal transcript levels. Human BRDT expression pattern differs from mouse BRDT expression. In human, BRDT is the only BET gene expressed exclusively in testicular germ cells. Its expression in elongated spermatids and ejaculated spermatozoa raises the possibility that it is involved in unidentified additional functions.

Immunohistochemical localization of transforming growth factor β1 and β2 in mouse testes during postnatal development

We examined age-related changes in the expression of transforming growth factor-β1 (TGF-β1) and transforming growth factor-β2 in mouse testes. The mice were assigned to three age groups: 35, 50, and 75 days old. Paraffin embedded testis sections were processed for the standard streptavidin biotin peroxidase complex immunohistochemistry method. TGF-β1 expression increased in aging round spermatids over the time studied. There was no expression in 35-day-old Leydig cells, whereas strong expression of TGF-β1 was observed in 50-day-old Leydig cells. Expression decreased in 75-day-old Leydig cells. TGF-β2 expression was weak in 35- and 50-day-old mouse spermatids, but expression was greater in 75-day-old elongated spermatids. In Leydig cells, TGF-β2 expression was strong in both 35- and 50-day-old mice, whereas the expression of TGF-β2 was less in 75-day-old Leydig cells. Our results suggest that TGF-β1 and TGF-β2 may play significant roles in testicular functions and germ cell development in mice.

Diet exposure to technical hexabromocyclododecane (HBCD) affects testes and circulating testosterone and thyroxine levels in American kestrels (Falco sparverius)

Hexabromocyclododecane (HBCD) is a high-production-volume, brominated flame-retardant that is used in items such as polystyrene foams. HBCD has been detected in the environment, wildlife tissues and in humans globally with some of the highest recorded levels in predatory birds. This study examined the effects of exposure to environmentally relevant levels of HBCD on the reproductive physiology of captive male American kestrels (Falco sparverius), a predatory bird. Two sets of males were used: one group not housed with females (unpaired: nc=12, nHBCD=10) and the second group housed with females (breeding: nc=10, nHBCD=20). All treatment birds were exposed to 0.51μg HBCD/g kestrel/day technical HBCD, and controls to safflower oil only, injected into their food during seasonal testicular development. Unpaired males were exposed for 3 weeks and euthanized for testicular analysis. Breeding males were exposed for 3 weeks prior to pairing and throughout the courtship period. The HBCD-exposed unpaired males had heavier testes (p≤0.017) and a trend towards more seminiferous tubules containing elongated spermatids (p=0.052). There was also a moderate increase in plasma testosterone concentrations (p=0.056) compared to controls. In breeding males, testosterone levels increased during courtship to culminate in higher levels than controls by the time the first egg was laid (p=0.010) and circulating free and total T4 was reduced throughout. The number of sperm cells reaching the perivitelline layer of the first egg for breeding males did not differ between the two groups. This study is the first report that HBCD exposure at environmentally relevant levels alters reproductive physiology in male birds and suggests that birds may be more sensitive to HBCD than mammals.

The RNA-binding protein ELAVL1/HuR is essential for mouse spermatogenesis, acting both at meiotic and postmeiotic stages

Posttranscriptional mechanisms are crucial to regulate spermatogenesis. Accurate protein synthesis during germ cell development relies on RNA binding proteins that control the storage, stability, and translation of mRNAs in a tightly and temporally regulated manner. Here, we focused on the RNA binding protein Embryonic Lethal Abnormal Vision (ELAV) L1/Human antigen R (HuR) known to be a key regulator of posttranscriptional regulation in somatic cells but the function of which during gametogenesis has never been investigated. In this study, we have used conditional loss- and gain-of-function approaches to address this issue in mice. We show that targeted deletion of HuR specifically in germ cells leads to male but not female sterility. Mutant males are azoospermic because of the extensive death of spermatocytes at meiotic divisions and failure of spermatid elongation. The latter defect is also observed upon HuR overexpression. To elucidate further the molecular mechanisms underlying spermatogenesis defects in HuR-deleted and -overexpressing testes, we undertook a target gene approach and discovered that heat shock protein (HSP)A2/HSP70-2, a crucial regulator of spermatogenesis, was down-regulated in both situations. HuR specifically binds hspa2 mRNA and controls its expression at the translational level in germ cells. Our study provides the first genetic evidence of HuR involvement during spermatogenesis and reveals Hspa2 as a target for HuR.

Spermatogonial stem cells in the testis of an endangered bovid: Indian black buck ( Antilope cervicapra L.)

Numerous wild bovids are facing threat of extinction owing to the loss of habitat and various other reasons. Spermatogonial stem cells (SSCs) represent the only germline stem cells in adult body that are capable of self-renewal and that can undergo differentiation to produce haploid germ cells. SSCs can, therefore, serve as a useful resource for preservation of germplasm of threatened and endangered mammals. The Indian black buck ( Antilope cervicapra L.) is a small Indian antelope that is listed as endangered by the Indian Wildlife Protection Act, 1972. Immunohistochemical analysis of testes tissues of black buck revealed the presence of spermatogonia that were specifically stained by lectin- Dolichos biflorus agglutinin (DBA). The expression of pluripotent cell-specific markers, NANOG and stage-specific embryonic antigen-1 (SSEA-1), was detected in spermatogonia. Interestingly, the expression of POU5F1 (OCT3/4) was absent from spermatogonia, however, it was detected in differentiating cells such as spermatocytes and round spermatids but not in elongated spermatids. The expression of NANOG protein was also present in spermatocytes but absent in round and elongated spermatids. Using the testis transplantation assay, stem cell potential of black buck spermatogonia was confirmed as indicated by the presence of colonized DBA-stained cells in the basal membrane of seminiferous tubules of xenotransplanted mice testis. The findings from this study suggest the presence of SSCs in the testis of an endangered bovid for the first time and open new possibility to explore the use of SSCs in conservation.