Impairment of spermatogenesis in transgenic mice with selective overexpression of Bcl-2 in the somatic cells of the testis

Integrated analysis of miRNA and mRNA expression profiles in testes of Landrace and Hezuo boars

Precocious puberty is closely related to testicular development and spermatogenesis, and there is increasing evidence that miRNAs are involved in regulation of testicular development and spermatogenesis. However, little is known about the regulation of microRNAs (miRNAs) during precocious maturation in Hezuo (HZ) boars. In this study, serum Testosterone (T), Estradiol (E₂), Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH) levels were detected in HZ and Landrace (LC) boars in the postnatal period at 30, 90, 120, 180, and 240 days, and the testes of HZ and LC boars at 30 and 120 days were used for histological observation. In addition, we performed small RNA-Seq to identify miRNA at sexual immaturity (30-days-old) and maturity (120-days-old) of HZ boar testis (using LC boar as control) to reveal the key miRNA in regulation of precocious puberty. Hormone assay results showed that high levels of T, E₂, FSH, and LH may be related to precocious sexual maturity of HZ boars, and that FSH may play an important function before sexual maturity. Histological observation showed that HZ boars developed earlier than LC boars and had reached sexual maturity at 120 days. Small RNA-Seq yielded a total of 359 exist miRNAs, 767 known miRNAs and 322 novel miRNAs in 12 samples; 549, 468, 133, and 247 differentially expressed (DE) miRNAs were identified between Ha vs. Hb, La vs. Lb, Ha vs. La, and Hb vs. Lb (log₂ fold change >1 and p < 0.05). Enrichment analysis showed that target genes of these DE miRNAs were enriched in many gene ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) signaling pathways (such as PI3K-Akt, Hippo and Rap1 signaling pathways) were related to testicular development and spermatogenesis. Further screening, some miRNAs (such as ssc-miR-29b, ssc-miR-199b, ssc-miR-383, ssc-miR-149, ssc-miR-615, and ssc-miR-370) were possibly associated with precocious puberty. These results provide new light on miRNA regulatory mechanisms involved in precocious puberty.

Maternal undernutrition during pregnancy and lactation increases transcription factors, ETV5 and GDNF, and alters regulation of apoptosis and heat shock proteins in the testis of adult offspring in the rat

We tested whether changes in Sertoli cell transcription factors and germ cell heat shock proteins (HSPs) are linked to the effects of maternal undernutrition on male offspring fertility. Rats were fed ad libitum with a standard diet (CONTROL) throughout pregnancy and lactation or with 50% of CONTROL intake throughout pregnancy (UNP) or lactation (UNL) or both periods (UNPL). After postnatal Day 21, 10 male pups per group were fed a standard diet ad libitum until postnatal Day 160 when testes were processed for histological, mRNA and immunohistochemical analyses. Compared with CONTROL: caspase-3 was increased in UNP and UNPL (P=0.001); Bax was increased in UNL (P=0.002); Bcl-2 (P<0.0001) was increased in all underfed groups; glial cell line-derived neurotrophic factor (P=0.002) was increased in UNP and UNL; E twenty-six transformation variant gene 5 and HSP70 were increased, and HSP90 was diminished in all underfed groups (P<0.0001). It appears that maternal undernutrition during pregnancy and lactation disrupts the balance between proliferation and apoptosis in germ cells, increasing germ cell production and perhaps exceeding the support capacity of the Sertoli cells. Moreover, fertility could be further compromised by changes in meiosis and spermiogenesis mediated by germ cell HSP90 and HSP70.

Investigating the Role of the microRNA-34/449 Family in Male Infertility: A Critical Analysis and Review of the Literature

There is a great body of evidence suggesting that in both humans and animal models the microRNA-34/449 (miR-34/449) family plays a crucial role for normal testicular functionality as well as for successful spermatogenesis, regulating spermatozoa maturation and functionality. This review and critical analysis aims to summarize the potential mechanisms via which miR-34/449 dysregulation could lead to male infertility. Existing data indicate that miR-34/449 family members regulate ciliogenesis in the efferent ductules epithelium. Upon miR-34/449 dysregulation, ciliogenesis in the efferent ductules is significantly impaired, leading to sperm aggregation and agglutination as well as to defective reabsorption of the seminiferous tubular fluids. These events in turn cause obstruction of the efferent ductules and thus accumulation of the tubular fluids resulting to high hydrostatic pressure into the testis. High hydrostatic pressure progressively leads to testicular dysfunction as well as to spermatogenic failure and finally to male infertility, which could range from severe oligoasthenozoospermia to azoospermia. In addition, miR-34/449 family members act as significant regulators of spermatogenesis with an essential role in controlling expression patterns of several spermatogenesis-related proteins. It is demonstrated that these microRNAs are meiotic specific microRNAs as their expression is relatively higher at the initiation of meiotic divisions during spermatogenesis. Moreover, data indicate that these molecules are essential for proper formation as well as for proper function of spermatozoa per se. MicroRNA-34/449 family seems to exert significant anti-oxidant and anti-apoptotic properties and thus contribute to testicular homeostatic regulation. Considering the clinical significance of these microRNAs, data indicate that the altered expression of the miR-34/449 family members is strongly associated with several aspects of male infertility. Most importantly, miR-34/449 levels in spermatozoa, in testicular tissues as well as in seminal plasma seem to be directly associated with severity of male infertility, indicating that these microRNAs could serve as potential sensitive biomarkers for an accurate individualized differential diagnosis, as well as for the assessment of the severity of male factor infertility. In conclusion, dysregulation of miR-34/449 family detrimentally affects male reproductive potential, impairing both testicular functionality as well as spermatogenesis. Future studies are needed to verify these conclusions.

Altered microRNAs expression levels of sperm and seminal plasma in patients with infertile ejaculates compared with normozoospermic males

Approximately 15% of couples are unable to conceive after one year of unprotected intercourse. Because sperm can be accessed with ease, it is reasonable to search for non-invasive biomarkers in semen. MicroRNAs are a family of short single-stranded non-coding RNA molecules that are capable of regulating gene expression and causing mRNA degradation. We studied the most common 11 spermatogenesis-related microRNAs expression levels in sperm and seminal plasma from patients with oligozoospermic or asthenozoospermic ejaculates, and in men with normozoospermic ejaculates. Five of these miRNAs were significantly upregulated and three were downregulated in infertile males compared to men with normozoospermic ejaculates. A statistically significant negative correlation was found between the sperm concentration and several microRNA expression level (let-7a, miR-7-1-3p, miR-141, miR-200a, and miR-429, p < 0.0001) both in sperm and in seminal plasma. We also found positive correlation between sperm concentration and some miRNA expression levels (miR-15b, miR-34b, and miR-122, p < 0.001) in sperm and in seminal plasma. This is the first study to demonstrate differences between sperm and seminal plasma miRNA expression level and to identify a correlation between the sperm concentration and miRNAs expression level. Therefore, these MiRNAs could have the potential be used as non-invasive biomarkers to diagnose males with impaired sperm production.

Comparative Transcriptomics Analysis of Testicular miRNA from Cryptorchid and Normal Horses

Simple Summary

The testis is an important organ for mammals, and testicular microRNA expression is associated with male fertility to a certain extent. Cryptorchidism is the failure of one or both testes to descend into the scrotal sac. It is a common congenital malformation in horses. The major clinical consequence of this abnormality is impaired fertility. The expression of testicular microRNAs is influenced by many factors, including high temperature and disease, in cryptorchid horses. Here, we investigated the microRNA expression levels of normal and retained testes. Their expression patterns showed significant differences. In addition, we obtained comprehensive expression data for equine testicular microRNA, which is fundamental information for further analysis.

Abstract

In the biological process of testicular spermatogenesis, the expression and interaction of many genes are regulated by microRNAs (miRNAs). However, comparisons of miRNA expression between descended testes (DTs) and undescended testes (UDTs) are rarely done in horses. In this study, we selected two UDTs (CKY2b and GU4b) from Chakouyi (CKY) and Guanzhong (GU) horses and eight DTs (GU1–3, CKY1, CKY3, CKY2a, GU4a, and GU5). Three groups were compared to evaluate expression patterns of testicular miRNA in stallion testes. Group 1 compared normal CKY horses and GU horses (CKY1 and CKY3 vs. GU1–3). Group 2 (CKY2a and GU4a (DTs) vs. CKY2b and GU4b (UDTs)) and group 3 (GU1–3, CKY1, CKY3 (DTs) vs. CKY2b and GU4b (UDTs)) compared the expression levels in unilateral retained testes to normal testes. The results show that 42 miRNAs (7 upregulated and 35 downregulated) had significantly different expression levels in both comparisons. The expression levels of eca-miR-545, eca-miR-9084, eca-miR-449a, eca-miR-9024, eca-miR-9121, eca-miR-8908e, eca-miR-136, eca-miR-329b, eca-miR-370, and eca-miR-181b were further confirmed by quantitative real-time PCR assay. The target genes of differentially expressed miRNAs in three comparisons were predicted, and the functions were annotated. The putative target genes of the 42 co-differentially expressed miRNAs were annotated to 15 functional terms, including metal ion binding, GTPase activator activity, zinc ion binding, intracellular, cytoplasm, and cancer pathways, and osteoclast differentiation. Our data indicate that the differentially expressed miRNAs in undescended testis suggests a potential role in male fertility and a relationship with cryptorchidism in horses. The discovery of miRNAs in stallion testes might contribute to a new direction in the search for biomarkers of stallion fertility.

Male infertility is associated with altered treatment course of men with cancer

This study aims to evaluate whether cancer treatments differ in infertile men compared to men who have undergone vasectomy and age-matched controls. We analyzed subjects from the Truven Health MarketScan Claims database from 2001 to 2009. Infertile men were identified through diagnosis and treatment codes. Comparison groups included vasectomized men and an age-matched cohort who were not infertile and had not undergone vasectomy. We considered cancer types previously associated with infertility that were diagnosed after the diagnosis of infertility. The treatment regimens were determined based on the presence of claims with CPT codes for chemotherapy (CTX), radiation (RTX) or surgical treatment (ST) for each entity in all study groups. Cases with multimodal treatments were also identified. As a result, CTX was similarly distributed among the infertile, vasectomized, and control groups. In contrast, RTX treatment length was shorter in infertile men. The frequency of multimodal treatment (i.e., radiation and chemotherapy) was twofold lower in men with infertility compared to other men. By focusing on treatment patterns for each cancer type among these groups, the duration of RTX and CTX was shorter in infertile men diagnosed with NHL compared to controls. We conclude that Infertile men diagnosed with cancer and specific cancer types experience different treatment courses, with shorter RTX and less combined RTX/CTX compared to fertile and vasectomized men. These differences could reflect differences in stage at presentation, biological behavior, or treatment responses in infertile men.

Overexpression of PRL7D1 in Leydig Cells Causes Male Reproductive Dysfunction in Mice

Prolactin family 7, subfamily d, member 1 (PRL7D1) is found in mouse placenta. Our recent work showed that PRL7D1 is also present in mouse testis Leydig cells, and the expression of PRL7D1 in the testis exhibits an age-related increase. In the present study, we generated transgenic mice with Leydig cell-specific PRL7D1 overexpression to explore its function during male reproduction. Prl7d1 male mice exhibited subfertility as reflected by reduced sperm counts and litter sizes. The testes from Prl7d1 transgenic mice appeared histologically normal, but the frequency of apoptotic germ cells was increased. Prl7d1 transgenic mice also had lower testosterone concentrations than wild-type mice. Mechanistic studies revealed that Prl7d1 transgenic mice have defects in the testicular expression of steroidogenic acute regulatory protein (STAR) and hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase cluster (HSD3B). Further studies revealed that PRL7D1 overexpression affected the expression of transferrin (TF) in Sertoli cells. These results suggest that PRL7D1 overexpression could lead to increased germ cell apoptosis and exert an inhibitory effect on testosterone production in Leydig cells by reducing the expression of certain steroidogenic-related genes. In addition, PRL7D1 appears to have important roles in the function of Sertoli cells, which, in turn, affects male fertility. We conclude that the expression level of PRL7D1 is associated with the reproductive function of male mice.

Mitochondria and mammalian reproduction

Mitochondria are cellular organelles with crucial roles in ATP synthesis, metabolic integration, reactive oxygen species (ROS) synthesis and management, the regulation of apoptosis (namely via the intrinsic pathway), among many others. Additionally, mitochondria in different organs or cell types may have distinct properties that can decisively influence functional analysis. In terms of the importance of mitochondria in mammalian reproduction, and although there are species-specific differences, these aspects involve both energetic considerations for gametogenesis and fertilization, control of apoptosis to ensure the proper production of viable gametes, and ROS signaling, as well as other emerging aspects. Crucially, mitochondria are the starting point for steroid hormone biosynthesis, given that the conversion of cholesterol to pregnenolone (a common precursor for all steroid hormones) takes place via the activity of the cytochrome P450 side-chain cleavage enzyme (P450scc) on the inner mitochondrial membrane. Furthermore, mitochondrial activity in reproduction has to be considered in accordance with the very distinct strategies for gamete production in the male and female. These include distinct gonad morpho-physiologies, different types of steroids that are more prevalent (testosterone, estrogens, progesterone), and, importantly, the very particular timings of gametogenesis. While spermatogenesis is complete and continuous since puberty, producing a seemingly inexhaustible pool of gametes in a fixed environment; oogenesis involves the episodic production of very few gametes in an environment that changes cyclically. These aspects have always to be taken into account when considering the roles of any common element in mammalian reproduction.

Functional role of progestin and the progesterone receptor in the suppression of spermatogenesis in rodents

Synthetic progestins such as levonorgestrel (LNG) are used in combination with testosterone (T) in male contraceptive clinical trials to suppress gonadotropins secretion, but whether progestins have additional direct effects on the testis are not known. This study aimed to examine the effect of a potent progestin, (LNG), alone or in combination with testosterone (T) on spermatogenesis in adult rats, and to evaluate the functional role of the progesterone receptors (PRs) in the testis. In comparison with a low dose of LNG treatment in adult rats for 4 weeks, T and T + LNG treatment decreased testicular sperm count to 64.1 and 40.2% of control levels respectively. LNG induced germ cell apoptosis at stages I-IV and XII-XIV; T increased apoptosis at stages VII-VIII; LNG + T treatment induced greater germ cell apoptosis at a wider range of seminiferous epithelial stages. RT-PCR and Western Blots showed that PR was present in testes and up-regulated during suppression of spermatogenesis induced by testicular hormonal deprivation. PR knockout (PRKO) mice had larger testes, greater sperm production, increased numbers of Sertoli and Leydig cells. Suppression of gonadotropin and intratesticular T by GnRH-antagonist treatment induced PR promoter driven LacZ expression in Leydig cells of PRKO mice. This suggests that GnRH-antagonist treatment while inducing germ cell apoptosis also up-regulates PR. We conclude that (i) LNG + T induced greater suppression of spermatogenesis through increase in germ cell apoptosis involving a wider range of seminiferous epithelial stages than either treatment alone, (ii) up-regulation of PR was associated with inhibition of spermatogenesis, (iii) PR knockout mice showed increased sperm production suggesting that testicular PR activated events play a physiological and pharmacological inhibitory role in the testis. These data support the hypothesis that in addition to its known suppressive effects on gonadotropins, progestins may have direct inhibitory actions on the testis.

Altered microRNA expression profiles of human spermatozoa in patients with different spermatogenic impairments

OBJECTIVE

To determine whether microRNAs are differentially expressed in men with normal versus impaired spermatogenesis, and to find a biomarker for accurate diagnosis of male infertility.

DESIGN

Microarray with real-time polymerase chain reaction (RT-PCR) validation.

SETTING

University research and clinical institutes.

PATIENT(S)

Male partner of selected couples (n = 27) who were undergoing assisted reproduction techniques for infertility treatment.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Statistically significantly altered microRNA expression profiles in normozoospermic versus asthenozoospermic and oligoasthenozoospermic men.

RESULT(S)

There were 50 miRNAs up-regulated and 27 miRNAs down-regulated in asthenozoospermic males. In oligoasthenozoospermic males, 42 miRNAs were up-regulated and 44 miRNAs down-regulated when compared with normozoospermic males. The miRNAs that exhibited the highest fold changes and area under the receiver operating characteristic curve were miR-34b, miR-122, and miR-1973 in samples from asthenozoospermic men and miR-34b, miR-34b*, miR-15b, miR-34c-5p, miR-122, miR-449a, miR-1973, miR-16, and miR-19a in samples from oligoasthenozoospermic men. Furthermore, quantitative RT-PCR assays on specific miRNAs, including miR-141, miR-200a, miR-122, miR-34b, miR-34c-5p, and miR-16, yielded results that were largely consistent with the microarray data.

CONCLUSION(S)

Our results reveal an extended number of miRNAs that were differentially expressed in asthenozoospermic and oligoasthenozoospermic males compared with normozoospermic males. These data provide evidence for analysis of miRNA profiles as a future diagnosing tool for male infertility.

Inactivation of AMPKα1 induces asthenozoospermia and alters spermatozoa morphology

AMP-activated protein kinase (AMPK), a key regulator of cellular energy homeostasis, is present in metabolic tissues (muscle and liver) and has been identified as a modulator of the female reproductive functions. However, its function in the testis has not yet been clearly defined. We have investigated the potential role of AMPK in male reproduction by using transgenic mice lacking the activity of AMPK catalytic subunit α1 gene [α1AMPK knockout (KO)]. In the testis, the α1AMPK subunit is expressed in germ cells and also in somatic cells (Sertoli and Leydig cells). α1AMPK KO male mice show a decrease in fertility, despite no clear alteration in the testis morphology or sperm production. However, in α1AMPK(-/-) mice, we demonstrate that spermatozoa have structural abnormalities and are less motile than in control mice. These spermatozoa alterations are associated with a 50% decrease in mitochondrial activity, a 60% decrease in basal oxygen consumption, and morphological defects. The α1AMPK KO male mice had high androgen levels associated with a 5- and 3-fold increase in intratesticular cholesterol and testosterone concentrations, respectively. High concentrations of proteins involved in steroid production (3β-hydroxysteroid dehydrogenase, cytochrome steroid 17 alpha-hydroxylase/17,20 lysate, and steroidogenic acute regulatory protein) were also detected in α1AMPK(-/-) testes. In the pituitary, the LH and FSH concentrations tended to be lower in α1AMPK(-/-) male mice, probably due to the negative feedback of the high testosterone levels. These results suggest that total α1AMPK deficiency in male mice affects androgen production and quality of spermatozoa, leading to a decrease in fertility.

The emerging role of matrix metalloproteases of the ADAM family in male germ cell apoptosis

Constitutive germ cell apoptosis during mammalian spermatogenesis is a key process for controlling sperm output and to eliminate damaged or unwanted cells. An increase or decrease in the apoptosis rate has deleterious consequences and leads to low sperm production. Apoptosis in spermatogenesis has been widely studied, but the mechanism by which it is induced under physiological or pathological conditions has not been clarified. We have recently identified the metalloprotease ADAM17 (TACE) as a putative physiological inducer of germ cell apoptosis. The mechanisms involved in regulating the shedding of the ADAM17 extracellular domain are still far from being understood, although they are important in order to understand cell-cell communications. Here, we review the available data regarding apoptosis during mammalian spermatogenesis and the localization of ADAM proteins in the male reproductive tract. We propose an integrative working model where ADAM17, p38 MAPK, protein kinase C (PKC) and the tyrosine kinase c-Abl participate in the physiological signalling cascade inducing apoptosis in germ cells. In our model, we also propose a role for the Sertoli cell in regulating the Fas/FasL system in order to induce the extrinsic pathway of apoptosis in germ cells. This working model could be applied to further understand constitutive apoptosis in spermatogenesis and in pathological conditions (e.g., varicocele) or following environmental toxicants exposure (e.g., genotoxicity or xenoestrogens).

Male germ cell apoptosis: regulation and biology

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.

BCL2 Ala43Thr is a functional variant associated with protection against azoospermia in a Han-Chinese population

Apoptosis is very common during various stages of mammalian germ cell development and differentiation, and the BCL2 gene is one of the most important apoptotic regulators. Although its genetic variants are reported to be involved in cancers and autoimmune diseases, little information is available regarding BCL2 polymorphisms in male spermatogenesis. In the present study, single nucleotide polymorphisms (SNPs) in coding regions of the BCL2 gene were examined in a hospital-based, case-control study including 198 infertile patients with idiopathic azoospermia and 183 fertile controls. Subsequently, a functional study was conducted for comparison of paclitaxel-induced cytotoxicity and apoptosis between the BCL2 variant and the wild type in vitro. Three SNPs were found in exon 2--A21G (rs1801018), G127A (rs1800477), and C300T (rs61733416)--with the latter first reported in the Han-Chinese population. The frequency of G127A (GA+AA) genotype was significantly lower in azoospermic, infertile men compared to the age-matched controls (P = 0.01). This genotype may confer a lower risk of azoospermia (adjusted odd ratio [OR] = 0.448, 95% confidence interval = 0.226-0.889). In addition, HeLa cells expressing the BCL2 Ala43Thr (G127A), similar to the control cells, were more sensitive to paclitaxel-induced cytotoxicity and apoptosis than those expressing wild-type BCL2. Consistently, the cleaved PARP and p-BCL2 proteins were subsequently increased after paclitaxel treatment, as also predicted by the bioinformatics analysis. Considering the decreased antiapoptotic function of BCL2, these results suggest that the Ala43Thr variant is associated with protection against azoospermia in the Han-Chinese population.

Microarray profiling of microRNAs expressed in testis tissues of developing primates

PURPOSE

MicroRNAs (miRNAs) are small non-coding RNA molecules that have been identified as potent regulators of gene expression. Recent studies indicate that miRNAs are involved in mammalian spermatogenesis but the mechanism of regulation is largely unknown.

METHODS

miRNA microarray was employed to compare miRNA expression profiles of testis tissues from immature rhesus monkey (Sample IR), mature rhesus monkey (Sample MR), and mature human (Sample MH). Real-time RT-PCR was used to confirm the changed miRNAs.

RESULTS

Twenty-six miRNAs were shared by samples IR/MR and IR/MH with differential expression patterns greater than three-fold difference. PicTar and TargetScan prediction tools predicted a number of target mRNAs, and some of these target genes predicted by miRNAs have been shown to associate with spermatogenesis.

CONCLUSIONS

Our results indicate that miRNAs are extensively involved in spermatogenesis and provide additional information for further studies of spermatogenetic mechanisms.

Mitogen-activated protein kinase signaling in male germ cell apoptosis in the rat

Programmed germ cell death is critical for functional spermatogenesis. Increased germ cell apoptosis can be triggered by various regulatory stimuli, including testicular hyperthermia or deprivation of gonadotropins and intratesticular testosterone. We have previously shown the involvement of the mitogen-activated protein kinase (MAPK) 14 in apoptotic signaling of male germ cells across species after hormone deprivation. This study investigates the role of MAPK14 in germ cell apoptosis in rats triggered by testicular hyperthermia. The contributions of the MAPK1/3 and the MAPK8 to male germ cell death were also examined after this intervention. We show that 1) testicular hyperthermia results in induction of both MAPK1/3 and MAPK14 but not MAPK8; 2) inhibition of MAPK1/3 has no effect on the incidence of heat-induced germ cell apoptosis, suggesting that MAPK1/3 signaling may be dispensable for heat-induced male germ cell apoptosis; and 3) activation of MAPK14 and BCL2 phosphorylation are critical for heat-induced male germ cell apoptosis in rats. Thus, unlike the hormone deprivation model, heat stress through activation of the MAPK14 signaling promotes germ cell apoptosis by provoking BCL2 phosphorylation, leading to its inactivation and the subsequent activation of the mitochondria-dependent death pathway. These novel findings point to a critical role of MAPK14 in stage- and cell-specific activation of male germ cell apoptosis triggered by hormone deprivation or heat stress.

Up-regulation of CD95 (Apo-1/Fas) is associated with spermatocyte apoptosis during the first round of spermatogenesis in the rat

Apoptosis plays a major role in controlling both the rate of sperm production and chromosomal abnormalities in adult male testes. However, little is known on the mechanisms controlling induction and execution of apoptosis under physiological conditions. In this work we have uncovered a major role for the cell death receptor Fas in both the extrinsic and intrinsic pathways in normal germ cell apoptosis. We show here that Fas levels increased significantly in a group of germ cell in 25 d old rats, which were identified as spermatocytes and only a few spermatogonia. In addition, we show that isolated spermatocytes expressing high levels of Fas display activation of caspase-8, -9, -3, -6 and -2, as well as increased levels of intracellular calcium and decreased pH, which coincides with stabilization of p53, and transcriptional activation of PUMA and Fas. Therefore, our data strongly suggests that transcriptional up regulation of Fas could predispose a group of spermatocytes to Fas ligand triggering apoptosis by the extrinsic and intrinsic pathway.

Molecular cloning of a novel rat gene Tsarg1, a member of the DnaJ/HSP40 protein family

Beginning with a mouse gene mTSARG3, which was related to apoptosis of spermatogenic cells, bioinformatics was applied and a predicted novel rat gene full-length cDNA sequence was attained. Gene-specific primers were designed for PCR in rat testis cDNA library. A new gene Tsarg1 (GenBank Accession No. AY380804) was cloned, which is related to apoptosis in rat spermatogenic cells. The gene whose full cDNA length is 1176 bp containing 8 exons and 7 introns is located in rat chromosome 1q32-1q33, which encoded a protein containing 316 amino acid residues and being a new member of HSP40 protein family since the sequence contains the highly conserved J domain, which is present in all DnaJ-like proteins and is supported to have a critical role in DnaJ-DnaK protein-protein interactions. The results of RT-PCR and Northern blot analysis showed that Tsarg1 was specifically expressed in rat testis, which probably inhibits rat testis spermatogenic cell apoptosis.

Follicular expression of a human beta-cell leukaemia/lymphoma-2 (Bcl-2) transgene does not decrease atresia or increase ovulation rate in swine

Transgenic (TG) gilts carrying a human Bcl-2 cDNA transgene driven by mouse inhibin-alpha subunit promoter were produced and evaluated to determine if ectopic expression of Bcl-2 in the ovaries would decrease the frequency of atresia in antral follicles and increase ovulation rate. Immunohistochemical analysis showed that the Bcl-2 transgene protein was expressed in granulosa and theca cells, in 86% of healthy and 54% of atretic follicles analysed in TG prepubertal and Day 50 pregnant gilts combined (n = 24). In contrast, Bcl-2 transgene protein was expressed in only 1.4% of healthy and 0% of atretic follicles in non-TG littermates (n = 13). Real-time reverse transcription-polymerase chain reaction analysis confirmed that human Bcl-2 was expressed in follicles of TG gilts. The atresia rate for the TG and non-TG groups did not differ (P > 0.05) for prepubertal (45 v. 59%) and Day 50 pregnant gilts (53 v. 52%) respectively. The mean +/- s.e.m. ovulation rate did not differ (P > 0.5) between TG (15.9 +/- 0.8, n = 12) and non-TG (16.4 +/- 0.6, n = 7) Day 50 pregnant gilts. The molecular basis of the failure of ectopic Bcl-2 expression to increase the ratio of healthy to atretic follicles is unknown, but it is possible that the activity of the mitochondrial-dependent cell death pathway was not neutralized by ectopic expression of human Bcl-2 or that other cell death pathways compensated for the decreased mitochondrial-dependent cell death.

Gene Regulation in Spermatogenesis

Mammalian spermatogenesis is a complex hormone-dependent developmental program in which a myriad of events must take place to ensure that germ cells reach their proper stage of development at the proper time. Many of these events are controlled by cell type- and stage-specific transcription factors. The regulatory mechanisms involved provide an intriguing paradigm for the field of developmental biology and may lead to the development of new contraceptives an and innovative routs to treat male infertility. In this review, we address three aspects of the genetic regulatory mechanism that drive spermatogenesis. First, we detail what is known about how steroid hormones (both androgens and estrogens) and their cognate receptors initiate and maintain mammalian spermatogenesis. Steroids act through three mechanistic routes: (i) direct activation of genes through hormone-dependent promoter elements, (ii) secondary transcriptional responses through activation of hormone-dependent transcription factors, and (iii) rapid, transcription-independent (nonclassical) events induced by steroid hormones. Second, we provide a survey of transcription factors that function in mammalian spermatogenesis, including homeobox, zinc-finger, heat-shock, and cAMP-response family members. Our survey is not intended to cover all examples but to give a flavor for the gamut of biological roles conferred by transcription factors in the testis, particularly those defined in knockout mice. Third, we address how testis-specific transcription is achieved. In particular, we cover the evidence for and against the idea that some testis-specific genes are transcriptionally silent in somatic tissues as a result of DNA methylation.

Mitochondria-Dependent Pathway Is Involved in Heat-Induced Male Germ Cell Death: Lessons from Mutant Mice1

The signaling events leading to apoptosis can be divided into two major pathways, involving either mitochondria (intrinsic) or death receptors (extrinsic). In a recent study, we have shown the involvement of the mitochondria-dependent apoptotic pathway in heat-induced male germ cell apoptosis in the rat. In additional studies, using the gld (generalized lymphoproliferation disease) and lprcg (lymphoproliferation complementing gld) mice, which harbor loss-of-function mutations in Fas L and Fas, respectively, we have shown that heat-induced germ cell apoptosis is not blocked, thus providing evidence that the Fas signaling system is not required for heat-induced germ cell apoptosis in the testis. In the present study, we have found that the initiation of apoptosis in wild-type mice was preceded by a redistribution of Bax from a cytoplasmic to paranuclear localization in heat-susceptible germ cells. The relocation of Bax is accompanied by sequestration of ultracondensed mitochondria into paranuclear areas of apoptotic germ cells, cytosolic translocation of mitochondrial cytochrome c and DIABLO, and is associated with activation of the initiator caspase 9 and the executioner caspase 3. Similar events were also noted in both gld and lprcg mice. Taken together, these results indicate that the mitochondria-dependent pathway is the key apoptotic pathway for heat-induced male germ cell death in mice.

Dysfunctional spermatogenesis in transgenic mice overexpressing bHLH-Zip transcription factor, Spz1

Spz1, a previously identified basic helix-loop-helix-leucine zipper (bHLH-Zip) transcription factor, is expressed specifically in the testis and epididymis of adult mice. However, Spz1's in vivo function is unclear. To study the function of Spz1 in vivo, we established Spz1 transgenic mice. Using this model, we were able to demonstrate that overexpression of Spz1 in the testis destroys tissue homeostasis at an early stage of spermatogenesis, which in turn induces apoptosis in germ cells and thus reduces male fertility. We identified that Spz1 is ectopically expressed in multiple tissues of transgenic male mice by Western blot analysis. In the testes of transgenic mice, Spz1 proteins were found to be overexpressed in both germ and somatic cells as determined by immunofluorescence staining. This upregulated cell proliferation was confirmed by in vivo BrdU incorporation in multinucleated gonocytes of 1-week-old transgenic mice. However, histological and immunohistochemical analyses indicated that these multinucleated germ cells in seminiferous tubules subsequently underwent apoptosis at 2 and 4 weeks of age through Fas/FasL- and ER stress-signaling pathways. Furthermore, germ cells surviving two cycles of meiosis suffered aberrant spermiogenesis, generating a large pool of abnormal spermatozoa. The transgenic male mice with reduced populations of normal spermatozoa produced offsprings of smaller litter sizes and became infertile at 6 months of age. These results suggest that cell proliferation in early spermatogenesis is critically regulated by multisignal pathways and unregulated cell proliferation at this stage, as induced by Spz1, leads to germ cell apoptosis. These results imply that Spz1 plays an important regulatory role during spermatogenesis.

Ultrastructural changes induced by leaves of Azadirachta indica (Neem) in the testis of albino rats

The present work was designed to study the effect of Azadirachta indica (Neem) powder on rat testis using the electron microscope. Male albino rats received 100 mg each A. indica leaf powder orally (by gavage). On alternate days, a second group of rats received 0.125 mg testosterone dipropionate intramuscularly. A third group received both A. indica leaf powder by gavage and testosterone dipropionate intramuscularly. Suitable controls were maintained. After autopsy, ultrastructural analysis of the testis revealed that animals treated with testosterone dipropionate showed well-developed Sertoli cells and germ cells with well-developed cytoplasmic organelles. By contrast, in A. indica-treated rats, intracellular spaces and vacuolization were observed in Sertoli cells; whereas in Leydig cells, cytoplasmic inclusions appeared diminished, and the configuration of granular endoplasmic reticulum appeared as a single unbranched tubule. In late spermatids, defects were observed in the mitochondrial sheath. The ultrastructural changes seen in the A. indica-treated group provide a clue that A. indica leaves might affect spermatogenesis through antispermatogenic and antiandrogenic properties.

Overexpression of Bcl-W in the testis disrupts spermatogenesis: revelation of a role of BCL-W in male germ cell cycle control

To explore physiological roles of BCL-W, a prosurvival member of the BCL-2 protein family, we generated transgenic (TG) mice overexpressing Bcl-w driven by a chicken beta-actin promoter. Male Bcl-w TG mice developed normally but were infertile. The adult TG testes displayed disrupted spermatogenesis with various severities ranging from thin seminiferous epithelium containing less germ cells to Sertoli cell-only appearance. No overpopulation of any type of germ cells was observed during testicular development. In contrast, the developing TG testes displayed decreased number of spermatogonia, degeneration, and detachment of spermatocytes and Sertoli cell vacuolization. The proliferative activity of germ cells was significantly reduced during testicular development and spermatogenesis, as determined by in vivo and in vitro 5'-bromo-2'deoxyuridine incorporation assays. Sertoli cells were structurally and functionally normal. The degenerating germ cells were TUNEL-negative and no typical apoptotic DNA ladder was detected. Our data suggest that regulated spatial and temporal expression of BCL-W is required for normal testicular development and spermatogenesis, and overexpression of BCL-W inhibits germ cell cycle entry and/or cell cycle progression leading to disrupted spermatogenesis.

The attractive Achilles heel of germ cell tumours: an inherent sensitivity to apoptosis-inducing stimuli

Testicular germ cell tumours (TGCTs) are extremely sensitive to cisplatin-containing chemotherapy. The rapid time course of apoptosis induction after exposure to cisplatin suggests that TGCT cells are primed to undergo programmed cell death as an inherent property of the cell of origin. In fact, apoptosis induction of germ cells in the testis is an important physiological mechanism to control the quality and quantity of the gametes produced. Although p53 protein is highly expressed in the majority of TGCTs, almost no p53 mutations have been detected. Interestingly, p53 overexpression is associated with loss of p21 and gain of mdm2 expression, which might indicate a partial loss in functionality of the p53 regulatory pathway in TGCTs. Besides p21, TGCTs often show low expression of other proteins involved in the regulation of cell cycle progression, such as the retinoblastoma protein and members of the INK4 family. It can be postulated that the deregulated G(1)-S phase checkpoint results in premature entry into the S phase upon DNA damage. In addition to Bcl-2 family members that are involved in the regulation of germ cell apoptosis in the normal testis via the mitochondrial death pathway, the Fas death pathway is also known to regulate apoptosis of germ cells in the testis. Since chemotherapy has been shown to activate the Fas death pathway and TGCTs co-express both Fas and its ligand FasL, TGCT cells might undergo apoptosis upon cisplatin treatment via autocrine or paracrine activation of the Fas system by FasL. The hypothesis suggested here is that the lack of cell cycle arrest following a cisplatin-containing treatment, together with the activation of the Fas death pathway and the mitochondrial death pathway, explains the rapid and efficient apoptosis of TGCT cells. Defining the mechanisms involved in the cisplatin sensitivity of TGCTs will provide tools to increase cisplatin sensitivity in other human tumours with acquired or intrinsic resistance.

Involvement of Fas system and active caspases in apoptotic signalling in testicular germ cells of ethanol-treated rats

The Fas system is involved in the regulation of germ cell apoptosis associated with testicular injury in experimental animals exposed to various insults. We tested the hypothesis that enhanced germ cell apoptosis mediated by the up-regulation of the Fas system and the activation of caspases may be involved in ethanol-induced testicular injury. Adult Wistar rats were fed either ethanol in Lieber-DeCarli liquid diet or an isocaloric control diet for 12 weeks. Marked Sertoli cell vacuolization and germ cell degeneration were observed in the testes of ethanol-treated rats (ETR) by both light and electron microscopy. Enhanced apoptosis of germ cells in ETR was detected by the terminal deoxynucleotidyl transferase-mediated deoxy-UTP nick end labelling (TUNEL) method, transmission electron microscopy, and was associated with elevated activity of caspase-3, -8 and -9. The expression levels of the Fas ligand (FasL) in Sertoli cells and of both Fas and caspase-3 in germ cells of ETR detected immunohistochemically were higher than those of the control testes. Furthermore, reverse transcriptase-polymerase chain reaction analysis demonstrated an increase in both Fas and FasL mRNA levels in ETR. Fas system up-regulation and the elevated activity of caspases in the testes of ETR may be a reflection of ethanol-induced testicular injury resulting in enhanced germ cells apoptosis, which may be involved in infertility associated with alcohol abuse.