Identification of human candidate genes for male infertility by digital differential display

Effects of Chromosomal Translocations on Sperm Count in Azoospermic and Oligospermic Cases

Purpose A number of mechanisms have been proposed for the effect of chromosomal translocations on spermatogenesis and sperm maturation. However, there are still numerous ambiguous issues regarding these two processes. The aim of this study is to evaluate the effect of chromosome break areas on sperm count in the light of the literature. Material and Methods The study was conducted on the data of 16 male patients with reciprocal or Robertsonian translocation among 152 patients who were admitted to Adana Numune Training and Research Hospital and Kanuni Sultan Süleyman Training and Research Hospital Genetic Diagnosis Centers between 2013 and 2016 due to azoospermia and oligospermia. Results 11 of these patients had reciprocal and five patients had Robertsonian translocations. All the patients with Robertsonian translocations were detected with azoospermia. Of the patients with reciprocal translocation, five of them were azoospermic and six of them were severe oligospermic. Conclusion A total of 21 chromosomal breakpoints were identified in the 11 patients with reciprocal translocations. These chromosomal breakpoints may contribute to the clarification of ambiguous issues related to spermatogenesis and sperm maturation. The results also showed the importance of genetic counselling in patients with translocations.

Functional redundancy and compensation: Deletion of multiple murine Crisp genes reveals their essential role for male fertility

Mammalian Cysteine-RIch Secretory Protein (CRISP) family includes four members present in sperm and reported to regulate Ca²⁺ channels and fertilization. Based on our previous observations using single knockouts models and suggesting the existence of functional compensation among CRISP proteins, we investigated their relevance for male fertility by generating multiple Crisp gene mutants by CRISPR/Cas9 technology. Whereas targeting of Crisp1 and Crisp3 yielded subfertile males with early embryo developmental defects, the same deletion in zygotes from fertile Crisp2^-/- .Crisp4^-/- mice led to the generation of both triple and quadruple knockout mice exhibiting a complete or severe disruption of male fertility due to a combination of sperm transport, fertilization, and embryo developmental defects linked to intracellular Ca²⁺ dysregulation. These observations reveal that CRISP proteins are essential for male fertility and organize in functional modules that contribute distinctly to fertility success, bringing insights into the mechanisms underlying functional redundancy/compensation in protein families and emphasizing the importance of generating multiple and not just single knockout which might be masking the true functional relevance of family genes.

Fertilization defects in sperm from Cysteine-rich secretory protein 2 (Crisp2) knockout mice: implications for fertility disorders

STUDY HYPOTHESIS

We hypothesize that fertility disorders in patients with aberrant expression of Cysteine-RIch Secretory Protein 2 (CRISP2) could be linked to the proposed functional role of this protein in fertilization.

STUDY FINDING

Our in vivo and in vitro observations reveal that Crisp2-knockout mice exhibit significant defects in fertility-associated parameters under demanding conditions, as well as deficiencies in sperm fertilizing ability, hyperactivation development and intracellular Ca(2+) regulation.

WHAT IS KNOWN ALREADY

Testicular CRISP2 is present in mature sperm and has been proposed to participate in gamete fusion in both humans and rodents. Interestingly, evidence in humans shows that aberrant expression of CRISP2 is associated with male infertility.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

A mouse line carrying a deletion in the sixth exon of the Crisp2 gene was generated. The analyses of the reproductive phenotype of Crisp2(-/-) adult males included the evaluation of their fertility before and after being subjected to unilateral vasectomy, in vivo fertilization rates obtained after mating with either estrus or superovulated females, in vitro sperm fertilizing ability and different sperm functional parameters associated with capacitation such as tyrosine phosphorylation (by western blot), acrosome reaction (by Coomassie Blue staining), hyperactivation (by computer-assisted sperm analysis) and intracellular Ca(2+) levels (by flow cytometry).

MAIN RESULTS AND THE ROLE OF CHANCE

Crisp2(-/-) males presented normal fertility and in vivo fertilization rates when mated with estrus females. However, the mutant mice showed clear defects in those reproductive parameters compared with controls under more demanding conditions, i.e. when subjected to unilateral vasectomy to reduce the number of ejaculated sperm (n = 5; P< 0.05), or when mated with hormone-treated females containing a high number of eggs in the ampulla (n ≥ 5; P< 0.01). In vitro fertilization studies revealed that Crisp2(-/-) sperm exhibited deficiencies to penetrate the egg vestments (i.e. cumulus oophorus and zona pellucida) and to fuse with the egg (n ≥ 6; P< 0.01). Consistent with this, Crisp2-null sperm showed lower levels of hyperactivation (n = 7; P< 0.05), a vigorous motility required for penetration of the egg coats, as well as a dysregulation in intracellular Ca(2+) levels associated with capacitation (n = 5; P< 0.001).

LIMITATIONS, REASONS FOR CAUTION

The analysis of the possible mechanisms involved in fertility disorders in men with abnormal expression of CRISP2 was carried out in Crisp2 knockout mice due to the ethical and technical problems inherent to the use of human gametes for fertilization studies.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings in mice showing that Crisp2(-/-) males exhibit fertility and fertilization defects under demanding conditions support fertilization defects in sperm as a mechanism underlying infertility in men with aberrant expression of CRISP2. Moreover, our observations in mice resemble the situation in humans where fertility disorders can or cannot be detected depending on the accumulation of own individual defects or the fertility status of the partner. Finally, the fact that reproductive defects in mice are masked by conventional mating highlights the need of using different experimental approaches to analyze male fertility.

STUDY FUNDING AND COMPETING INTERESTS

This study was supported by the World Health Organization (H9/TSA/037), the National Research Council of Argentina (PIP 2009-290), the National Agency for Scientific and Technological Promotion of Argentina (PICT 2011, 2023) and the Rene Baron Foundation to P.S.C. and by the MEXT of Japan to M.I. The authors declare that there are no conflicts of interest.

Expression and localization of testis developmental related gene 1 (TDRG1) in human spermatozoa

Testis-specific proteins, synthesized during spermatogenesis and spermiogenesis, are necessary for spermatid differentiation and/or for mature sperm function during fertilization. However, majority of these genes have neither been identified nor fully characterized. Testis developmental related gene 1 (TDRG1), a newly identified human testis-specific gene, encodes a 100-amino-acid protein without any characterized protein domains, and it may play a role in spermatogenesis. However, whether this human-specific protein is important for mature sperm function remains unclear. As an initial effort, in this study, we aimed to systematically investigate the expression and localization of TDRG1 in normal human spermatozoa. Thus, immunohistochemistry was used to analyze the distribution of TDRG1 in human testis. Reverse transcription-polymerase chain reaction, western blot analysis and indirect immunofluorescence were used to determine the expression and localization of TDRG1 in normal human spermatozoa. The immunohistochemistry results showed that the TDRG1 protein was expressed in spermatogenic cells in the seminiferous tubules of human testis. Interestingly, the TDRG1 was more abundant in spermatogenic cells at the late stages of spermatogenesis. The TDRG1 antibody specifically recognized an 11-kDa protein only in soluble extracts from normal human spermatozoa. Indirect immunofluorescence assays indicated that TDRG1 located in the midpiece, principal piece and flagellum of normal human spermatozoa. In conclusion, TDRG1 was found not only in spermatogonia, but also in spermatozoa. The localization of TDRG1 in human normal spermatozoa implies its potential regulatory role in sperm motility.

Utilization of digital differential display to identify differentially expressed genes related to rumen development

This study aimed to identify the genes associated with the development of the rumen epithelium by screening for candidate genes by digital differential display (DDD) in silico. Using DDD in NCBI's UniGene database, expressed sequence tag (EST)-based gene expression profiles were analyzed in rumen, reticulum, omasum, abomasum and other tissues in cattle. One hundred and ten candidate genes with high expression in the rumen were derived from a library of all tissues. The expression levels of 11 genes in all candidate genes were analyzed in the rumen, reticulum, omasum and abomasum of nine Japanese Black male calves (5-week-old pre-weaning: n = 3; 15-week-old weaned calves: n = 6). Among the 11 genes, only 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), aldo-keto reductase family 1, member C1-like (AKR1C1), and fatty acid binding protein 3 (FABP3) showed significant changes in the levels of gene expression in the rumen between the pre- and post-weaning of calves. These results indicate that DDD analysis in silico can be useful for screening candidate genes related to rumen development, and that the changes in expression levels of three genes in the rumen may have been caused by weaning, aging or both.

Cytochrome P450-2D6*4 polymorphism seminal relationship in infertile men

This study aimed to assess cytochrome (CY) P450-2D6*4 polymorphism relationship with semen variables in infertile men. In all, 308 men were included; fertile normozoospermia (N) (n = 77), asthenozoospermia (A) (n = 70), asthenoteratozoospermia (AT) (n = 75) and oligoasthenoteratozoospermia (OAT) (n = 86). They were subjected to history taking, clinical examination, semen analysis, sperm acrosin activity, seminal malondialdehyde (MDA) and CYP450-2D6*4 genotyping. CYP450-2D6*4 wild-type allele was represented in 76.5% of N, 70% of A, 66.7% of AT and 57.7% of OAT men where homozygous gene mutation was present in 5.9% of N, 20% of A, 26.6% of AT and 26.9% of OAT men, respectively. Sperm acrosin activity, sperm concentration, sperm motility, linear sperm velocity and sperm normal forms were significantly higher, and seminal MDA level was significantly lower in men with CYP450-2D6*4 wild-type allele compared with men with homozygous mutation. It is concluded that CYP450-2D6*4 wild-type allele has higher frequency where homozygous-type allele has lower frequency in N men compared with A, AT and OAT men. Sperm acrosin activity index, sperm concentration, sperm motility, linear sperm velocity and sperm normal forms were significantly higher, and seminal MDA level was significantly lower in men with CYP450-2D6*4 wild-type allele compared with men with homozygous mutation.

Presentation and treatment of subfertile men with balanced translocations: the cleveland clinic experience

INTRODUCTION

Balanced chromosomal translocations are a relatively common (2-7%) finding among infertile couples. We report clinical features of males with translocations at our institution.

MATERIALS AND METHODS

Data was collected on men presenting for infertility evaluation between July 2006 March 2010, including presentation, medical history, and infertility treatments. Criteria for genetic evaluation, consisting of karyotype and Y-linked microdeletion assay, included severe oligozoospermia or azoospermia (sperm concentration < 2.5×106/ml) or a history of recurrent miscarriages.

RESULTS

Of the 4,612 patients in our male infertility clinic 306 met criteria for genetic evaluation. Three patients had a balanced translocation, of which 2 had Robertsonian translocations, and 1 had a balanced translocation. One patient had normal bulk semen parameters, normal volume azoospermia, and oligoasthenoteratozoospermia. All patients were offered medical genetics consultation. Potential pregnancy outcomes were evaluated using a predictive software package. One patient had intratubular germ cell neoplasia and underwent orchiectomy; subsequent fertility evaluation has been deferred. The other 2 are considering in-vitro fertilization with pre-implantation genetic evaluation.

CONCLUSIONS

Given the low incidence of balanced translocations detected in our population, better clinical indicators other than semen parameters or history of recurrent pregnancy loss are needed to determine screening for this finding.

Characterization of a novel human testis-specific gene: testis developmental related gene 1 (TDRG1)

Spermatogenesis is a highly coordinated physiological process that requires the correct expression and functions of thousands of developmentally regulated genes. The regulation of spermatogenesis is not well defined, since majority of the related genes have neither been identified nor fully characterized. Hence, it is meaningful to identify and characterize these genes to reveal the mechanism underlying spermatogenesis. In this study, using digital differential display, we identified a novel human testis-specific gene, testis developmental related gene 1 (TDRG1, GenBank DQ168992), via electronic subtraction of human testis UniGene databases from those of non-reproductive tissues. The transcript of the TDRG1 gene has an open-reading frame that encodes 100 amino acids. We next prepared the anti-TDRG1 monoclonal antibody 10B6 and confirmed that it specifically recognizes an 11-kDa protein in the tissue extracts from an adult human testicular sample (age 31 years) by Western blot analysis. RT-PCR coupled with immunohistochemistry of human tissues demonstrated that TDRG1 is exclusively expressed in the testis but not in any other non-reproductive tissues. TDRG1 is mainly located in spermatogenic cells in seminiferous tubules of adult testis. Furthermore, TDRG1 shows the highest expression level in human post-puberty testis, with the expression levels decreasing afterwards with aging. Importantly, TDRG1 mRNA is undetectable in the fetal testis, as judged by RT-PCR. In conclusion, TDRG1 is a developmentally regulated testicular-specific gene. We suggest that TDRG1, a newly identified testis-specific gene, may play important roles in human spermatogenesis.

The significance of Y chromosome microdeletion analysis in subfertile men with clinical variocele

INTRODUCTION

The aim of study is determining the cost-effectiveness of detection analysis in the presence of exceptional patients who have mild semen disorders, and beware of unnecessary varicocele repairs; and to ascertain whether patients with clinical varicocele should undergo Y chromosome (Yq) microdeletion analysis as a routine procedure.

MATERIAL AND METHODS

Varicocele with reflux was diagnosed in 51 male patients with subfertility symptoms upon physical examination (PE), confirmed by scrotal colour-Doppler ultrasound (CDU). After cytogenetic examination, Yq microdeletion analysis was performed on the peripheral blood samples using Promega Y Chromosome Deletion Detection System Version 2. Varicocele repair was performed under general anaesthesia with optical magnification (3-fold) through a subinguinal approach.

RESULTS

The mean age of the patients was 27.9. Values of semen concentration ranged from 0 to 72 million/ml, motility from 0 to 65% (A + B) and Kruger from 0% to 18%. The PE revealed normal size and consistency in the bilateral testicles. All patients were cytogenetically normal. However, Yq microdeletion was detected in 2 patients, 1 with mild oligoteratozoospermia and partial AZFb deletion (sY121) and the second patient with severe oligozoospermia and partial AZFc deletion (sY254 and sY255), and they were not subjected to varicocelectomy.

CONCLUSIONS

The routine performance of pre-operative Yq microdeletion analysis in patients with clinical varicocele does not seem to be cost-effective but the omission of patients with mild oligozoospermia would have subjected them to an unnecessary varicocelectomy and/or further ICSI applications and also would have caused the failure of referral for genetic counselling.

Epigenetic abnormality of SRY gene in the adult XY female with pericentric inversion of the Y chromosome

In normal ontogenetic development, the expression of the sex-determining region of the Y chromosome (SRY) gene, involved in the first step of male sex differentiation, is spatiotemporally regulated in an elaborate fashion. SRY is expressed in germ cells and Sertoli cells in adult testes. However, only few reports have focused on the expressions of SRY and the other sex-determining genes in both the classical organ developing through these genes (gonad) and the peripheral tissue (skin) of adult XY females. In this study, we examined the gonadal tissue and fibroblasts of a 17-year-old woman suspected of having disorders of sexual differentiation by cytogenetic, histological, and molecular analyses. The patient was found to have the 46,X,inv(Y)(p11.2q11.2) karyotype and streak gonads with abnormally prolonged SRY expression. The sex-determining gene expressions in the patient-derived fibroblasts were significantly changed relative to those from a normal male. Further, the acetylated histone H3 levels in the SRY region were significantly high relative to those of the normal male. As SRY is epistatic in the sex-determination pathway, the prolonged SRY expression possibly induced a destabilizing effect on the expressions of the downstream sex-determining genes. Collectively, alterations in the sex-determining gene expressions persisted in association with disorders of sexual differentiation not only in the streak gonads but also in the skin of the patient. The findings suggest that correct regulation of SRY expression is crucial for normal male sex differentiation, even if SRY is translated normally.

TSEG-1, a novel member of histone H2A variants, participates in spermatogenesis via promoting apoptosis of spermatogenic cells

A novel variant of histone H2A, named as testis specific expressed gene 1 (TSEG-1, approved symbol: H2afb1), was identified from adult mouse testis. The TSEG-1 gene is 610-bp in length and consists of one exon. TSEG-1 transcript was robustly and exclusively expressed in adult mouse testis, mainly in spermatocytes. In developmental testis, the TSEG-1 transcript was robustly expressed since postnatal day (P) 21, peaked at P30, and gradually decreased in the testis of aging mouse. The surgical cryptorchidism mouse model showed an increase in the TSEG-1 expression, accompanied by enhanced apoptosis of spermatogenic cells. The EGFP-tagged TSEG-1 protein is located in the nuclei of cultured spermatocytes (GC-2spd cells). Transfection of TSEG-1 into GC-2spd cells resulted in suppressed cell viabilities, increased apoptosis, and decreased mitochondrial membrane potential. Intratesticular injection of TSEG-1 resulted in increased apoptosis of spermatogenic cells in vivo. These results suggest that TSEG-1 may participate in the spermatogenesis via regulating the apoptosis of spermatogenic cells.

The CAP superfamily: cysteine-rich secretory proteins, antigen 5, and pathogenesis-related 1 proteins--roles in reproduction, cancer, and immune defense

The cysteine-rich secretory proteins, antigen 5, and pathogenesis-related 1 proteins (CAP) superfamily members are found in a remarkable range of organisms spanning each of the animal kingdoms. Within humans and mice, there are 31 and 33 individual family members, respectively, and although many are poorly characterized, the majority show a notable expression bias to the reproductive tract and immune tissues or are deregulated in cancers. CAP superfamily proteins are most often secreted and have an extracellular endocrine or paracrine function and are involved in processes including the regulation of extracellular matrix and branching morphogenesis, potentially as either proteases or protease inhibitors; in ion channel regulation in fertility; as tumor suppressor or prooncogenic genes in tissues including the prostate; and in cell-cell adhesion during fertilization. This review describes mammalian CAP superfamily gene expression profiles, phylogenetic relationships, protein structural properties, and biological functions, and it draws into focus their potential role in health and disease. The nine subfamilies of the mammalian CAP superfamily include: the human glioma pathogenesis-related 1 (GLIPR1), Golgi associated pathogenesis related-1 (GAPR1) proteins, peptidase inhibitor 15 (PI15), peptidase inhibitor 16 (PI16), cysteine-rich secretory proteins (CRISPs), CRISP LCCL domain containing 1 (CRISPLD1), CRISP LCCL domain containing 2 (CRISPLD2), mannose receptor like and the R3H domain containing like proteins. We conclude that overall protein structural conservation within the CAP superfamily results in fundamentally similar functions for the CAP domain in all members, yet the diversity outside of this core region dramatically alters target specificity and, therefore, the biological consequences.

Underlying karyotype abnormalities in IVF/ICSI patients

Cytogenetic investigations are performed in couples asking for IVF or intracytoplasmic sperm injection (ICSI) treatment. These serve a diagnostic purpose because male or female infertility might have a chromosomal origin. Chromosomal aberrations found in these patients include numerical abnormalities, such as Klinefelter syndrome, XYY karyotype or Turner syndrome and its variants; sex reversions, such as XX males or XY females; and also structural abnormalities, such as Robertsonian or reciprocal translocations and inversions. Finding the chromosomal origin of infertility in a patient also has a prognostic value because it aids the management of pregnancies obtained after IVF or ICSI and may lead to a proposal of prenatal or preimplantation genetic diagnosis.

Genetic and epigenetic risks of intracytoplasmic sperm injection method

Pregnancies achieved by assisted reproduction technologies, particularly by intracytoplasmic sperm injection (ICSI) procedures, are susceptible to genetic risks inherent to the male population treated with ICSI and additional risks inherent to this innovative procedure. The documented, as well as the theoretical, risks are discussed in the present review study. These risks mainly represent that consequences of the genetic abnormalities underlying male subfertility (or infertility) and might become stimulators for the development of novel approaches and applications in the treatment of infertility. In addition, risks with a polygenic background appearing at birth as congenital anomalies and other theoretical or stochastic risks are discussed. Recent data suggest that assisted reproductive technology might also affect epigenetic characteristics of the male gamete, the female gamete, or might have an impact on early embryogenesis. It might be also associated with an increased risk for genomic imprinting abnormalities.

Ontogeny and cellular localization of SRY transcripts in the human testes and its detection in spermatozoa

The sex-determining region on the Y (SRY) gene is unequivocally designated as the testis-determining factor in mammals; however, its roles beyond sex determination, if any, have been hitherto unknown. To determine whether SRY has any roles beyond sex determination, herein the expression of SRY mRNA was investigated in the midtrimester human fetal, infantile and adult testes as well as in ejaculated spermatozoa. High levels of SRY transcripts were in situ localized to the Sertoli cells of the developing testis at 9 weeks of gestation, and the expression persisted at comparable levels throughout the midtrimester (until 22 weeks) and also in the testis of an infant at 3 months of age. The germ cells and other somatic cells in the testes of fetuses and the infant were negative for SRY expression. The mRNA for SRY was detected in the spermatogenic cells, particularly the spermatogonia and the round spermatids; the expression was negligible in the meiotic stages. A single transcript of approximately 1.2 kb was detected in the adult testes and isolated spermatogonial cells. In the adult testis, in situ hybridization (ISH) studies revealed a switch in the cellular localization of SRY transcripts. SRY transcripts were also demonstrable by RT-PCR of RNA from ejaculated human spermatozoa. ISH revealed the presence of SRY transcripts in the midpiece of 50% of ejaculated sperm. These results suggest that SRY may have extensive roles in male reproductive physiology, such as maturation of fetal testis, spermatogenesis, sperm maturation and early embryonic development.

Purification and refolding of a novel cancer/testis antigen BJ-HCC-2 expressed in the inclusion bodies of Escherichia coli

BJ-HCC-2 is one of the cancer/testis antigens that may be the most promising targets for tumor immunotherapy. To investigate the expression of BJ-HCC-2 protein in tumor cells and its capacity to elicit CTL response, the recombinant protein of BJ-HCC-2 was expressed in the inclusion bodies in Escherichia coli. The inclusion bodies were solubilized effectively with 0.3% N-lauroyl sarcosine in alkaline buffer. Under this denatured form, the BJ-HCC-2 protein carrying 6x histidine tag was purified with Ni-NTA affinity chromatography in a single step with a purity of over 97%. The yield of the purified protein was about 78%. The purified recombinant protein was refolded in a simple way. The correct refolding of the recombinant protein was verified in the recovery of its secondary and tertiary structures as assessed by circular dichroism and fluorescence emission spectra. The recovery rate of refolded protein was 92.1%. The renatured protein displayed its immunoreactivity with the antibodies to BJ-HCC-2 protein by Western blotting. This method of protein purification and refolding is easy to manipulate and may be applicable to the hydrophobic proteins that are unable to be purified by other methods.

The mammalian testis-specific thioredoxin system

Redox control of cell physiology is one of the most important regulatory mechanisms in all living organisms. The thioredoxin system, composed of thioredoxin and thioredoxin reductase, has emerged as a key player in cellular redox-mediated reactions. For many years, only one thioredoxin system had been described in higher organisms, ubiquitously expressed in the cytoplasm of eukaryotic cells. However, during the last decade, we and others have identified and characterized novel thioredoxin systems with unique properties, such as organelle-specific localization in mitochondria or endoplasmic reticulum, tissue-specific distribution mostly in the testis, and features novel for thioredoxins, such as microtubule-binding properties. In this review, we will focus on the mammalian testis-specific thioredoxin system that comprises three thioredoxins exclusively expressed in spermatids (named Sptrx-1, Sptrx-2, and Sptrx-3) and an additional thioredoxin highly expressed in testis, but also present in lung and other ciliated tissues (Txl-2). The implications of these findings in the context of male fertility and testicular cancer, as well as evolutionary aspects, will be discussed.

Identification of novel genes expressed during spermatogenesis in stage-synchronized rat testes by differential display

The molecular mechanism regulating spermatogenesis at different developmental stages remains largely unknown. In a vitamin A-deficiency (VAD) rat model, five distinct histologically defined, stage-synchronized testes: (i) resting spermatogonia and preleptotene spermatocytes at Day 0 of post-vitamin A treatment (PVA); (ii) early pachytene spermatocytes at Day 7 PVA; (iii) late pachytene at Day 15 PVA; (iv) round spermatids at Day 25 PVA; and (v) elongated spermatids at Day 35 PVA were used to study gene expression profiles by mRNA differential display. Twenty-four differentially expressed cDNA fragments were identified and cloned; oligonucleotide sequence analyses indicated that there are 12 novel gene sequences, half of which share no apparent match in current GenBank/EMBL databases. Other 12 VAD clones share sequence homology to membrane channel and transport, transcription and translation, cell cycle and morphogenesis, inducer and transducer, surface or secreted glycoproteins or enzymes, and other miscellaneous molecules. Semi-quantitative RT-PCR analyses against different stages of VAD testes demonstrated: (i) restricted expression of VAD1.2 and 1.3 (novel) on Day 25 PVA when round spermatids form; (ii) escalating pattern of VAD12 (Cx43) in Sertoli cells; and (iii) relative constant levels of VAD4 (A5D3), VAD26.1 (ribonuclease), and VAD27 (GRP8) in spermatogenesis.

Mutational analysis of the human FATE gene in 144 infertile men

The FATE gene maps to Xq28 where one case of a translocation breakpoint has been found in an infertile man. Moreover, the FATE promoter contains a putative SF-1-binding site, and FATE has been proposed as representing a target gene of SF-1 in testicular development or germ cell differentiation. This study presents a complete mutational screening of the FATE gene in a random group of 144 infertile males. Four polymorphisms and two mutations were found. Three of the polymorphisms, viz., 741C-->T, 905A-->C, and 3985C-->T, occurred in exon 5 and intron 2 and did not alter the deduced polypeptide. One polymorphism resulted in the conservative amino acid exchange, A10 V, in 16.0% of the patients. This substitution occurred with similar frequencies in the control groups, indicating that the mutation does not affect fertility in men or women. The two mutations caused the non-conservative amino acid substitutions S125R (patient 1) and I34T (patient 2). A family study (patient 1) revealed, however, that S125R was inherited and that a fertile male family member carried the mutation. Patient 2 did not have relevant family members who could be examined. Thus, this study has shown that only 1.4% of infertile men have mutations in the FATE gene, and that some of these mutations do not singly cause infertility. Hence, FATE may not play an important role in the disease-state of infertile men attending fertility clinics. However, FATE mutations cannot be excluded as being a contributing factor in some cases of male infertility.

[Genetic origin of spermatogenesis impairments: clinical aspects and relationships with mouse models of infertility]

Human spermatogenesis failures appear frequently as idiopathic and may be due to genetic causes. Mutations of genes involved in the hypothalamic/pituitary control of spermatogenesis have been described and account for several types of hypogonadotropic hypogonadism. Chromosomal abnormalities found in infertile patients are either gonosomal aneuploidies or structural anomalies which interfere with the normal chromosome behaviour at meiosis and lead to germ cell breakdown. Microdeletions of the Y chromosome are often undetectable at karyotype and are responsible for the loss of genes which compose the AZF factor. The increase in the number of mouse models of infertility will allow the description of many human genes involved in the spermatogenesis process provided that a detailed analysis of their genotype-phenotype relationships is performed.

Nurit, a novel leucine-zipper protein, expressed uniquely in the spermatid flower-like structure

Spermatozoa formation involves drastic morphological and cellular reconstructions. However, the molecular mechanisms driving this process remain elusive. We describe the cloning of a novel murine spermatid-specific gene, designated nurit, identified in a two-hybrid screen for proteins that binds the Nek1 kinase. Nurit protein harbors a leucine-zipper motif, and two additional coiled-coil regions. The C-terminal coiled-coil domain mediates homodimerization of the protein. Nurit homologues are found in primates, pig and rodents. nurit is transcribed through the elongation stage of the spermatids, but is absent from mature spermatozoa. Interestingly, immunogold electron microscopy revealed that the protein is restricted, from its first detectable appearance, to a unique spermatid organelle called the 'flower-like structure'. The function of this structure is unknown, though it may be involved in transporting proteins designated to be discarded via the residual bodies. Nurit is the first marker of the flower-like structure, and its study may provide an excellent opportunity to dissect the function of this organelle.

Hormonal genomics

The availability of the human genomic sequence is changing the way in which biological questions are addressed. Based on the prediction of genes from nucleotide sequences, homologies among their encoded amino acids can be analyzed and used to place them in distinct families. This serves as a first step in building hypotheses for testing the structural and functional properties of previously uncharacterized paralogous genes. As genomic information from more organisms becomes available, these hypotheses can be refined through comparative genomics and phylogenetic studies. Instead of the traditional single-gene approach in endocrine research, we are beginning to gain an understanding of entire mammalian genomes, thus providing the basis to reveal subfamilies and pathways for genes involved in ligand signaling. The present review provides selective examples of postgenomic approaches in the analysis of novel genes involved in hormonal signaling and their chromosomal locations, polymorphisms, splicing variants, differential expression, and physiological function. In the postgenomic era, scientists will be able to move from a gene-by-gene approach to a reconstructionistic one by reading the encyclopedia of life from a global perspective. Eventually, a community-based approach will yield new insights into the complexity of intercellular communications, thereby offering us an understanding of hormonal physiology and pathophysiology.

Identification of target messenger RNA substrates for the murine deleted in azoospermia-like RNA-binding protein

The murine autosomal deleted in azoospermia-like protein (mDAZL) is a germ cell-restricted RNA-binding protein essential for sperm production. Homozygous disruption of the mDAZL gene results in the absence of germ cells beyond the spermatogonial stage. Progress into the function of DAZL in spermatogenesis has been hampered without identification of the cognate mRNA substrates that it binds to and regulates. Using the isolation of specific nucleic acids associated with proteins (SNAAP) technique recently developed in our lab, we identified mRNAs from testis that were specifically bound by mDAZL. One mRNA encoded the Tpx-1 protein, a testicular cell adhesion protein essential for the progression of spermatogenesis. A 26-nucleotide region necessary and sufficient to bind mDAZL was found within additional mRNAs isolated by the screen. These included mRNA encoding Pam, a protein associated with myc; GRSF1, an mRNA-binding protein involved in translation activation, and TRF2, a TATA box-binding protein-like protein involved in transcriptional regulation. Each mRNA containing the mDAZL binding site was specifically bound by mDAZL. A similar sequence is also present in the Cdc25A mRNA, a threonine/tyrosine phosphatase involved in cell cycle progression. The mDAZL and Cdc25A homologues are functionally linked in Drosophila and are necessary for spermatogenesis. Our demonstration that Tpx-1 and Cdc25A mRNAs are bound by mDAZL suggests that mDAZL regulates a subset of mRNAs necessary for germ cell development and cell cycle progression. Understanding how mDAZL regulates the target mRNAs will provide new insights into spermatogenesis, strategies for therapeutic intervention in azoospermic patients, and novel approaches for male contraception.

Human FATE is a novel X-linked gene expressed in fetal and adult testis

Previously, we identified a partial cDNA sequence of a novel human transcript, designated fetal and adult testis expressed transcript (FATE). FATE is testis-specific in fetal life and co-expressed with SRY in a 7 weeks old fetal testis, suggesting a function in early testicular differentiation. Herein, full-length cDNA clones of human and porcine FATE were isolated and the gene structure and promoter region of the human FATE gene was characterized. The human FATE gene, which maps to Xq28, consists of five exons spanning approximately 7 kb of genomic DNA. Examination of 1 kb of the FATE promoter region revealed the presence of a putative steroidogenic factor 1 (SF-1) binding site at position -79 to -71 upstream of the transcription start site. We propose that FATE might represent a novel target gene of SF-1 in human testicular differentiation and/or germ cell development.