Reciprocal regulation of the mouse protamine genes by the orphan nuclear receptor germ cell nuclear factor and CREMtau

NR6A1 regulates lipid metabolism through mammalian target of rapamycin complex 1 in HepG2 cells

Background

Lipogenesis is required for the optimal growth of many types of cancer cells, it is shown to control the biosynthesis of the lipid bilayer membrane during rapid proliferation and metastasis, provides cancer cells with signaling lipid molecules to support cancer development and make cancer cells more resistant to oxidative stress-induced cell death. Though multiple lipogenic enzymes have been identified to mediate this metabolic change, how the expression of these lipogenic enzymes are transcriptionally regulated remains unclear.

Methods

Gain- and loss-of-function experiments were conducted to assess the role of transcriptional repressor, nuclear receptor sub-family 6, group A, member 1 (NR6A1) in HepG2 cells. RT-qPCR method was performed to investigate target gene of NR6A1. Western blot was employed to determine the mechanisms by which NR6A1 regulates lipid accumulation in HepG2 cells.

Results

We provide evidence that NR6A1 is a novel regulator of lipid metabolism in HepG2 cells. NR6A1 knockdown can increase lipid accumulation as well as insulin-induced proliferation and migration of HepG2 cells. The lipogenic effect correlated well with the expression of lipogenic genes, including fatty acid synthase (FAS), diglyceride acyltransferase-2 (DGAT2), malic enzyme 1 (ME1), microsomal triglyceride transfer protein (MTTP) and phosphoenolpyruvate carboxykinase (PEPCK). NR6A1 knockdown also increased the expression of carnitine palmitoyltransferase 1A (CPT1a), the rate-limiting enzyme in fatty acid oxidation. Furthermore, NR6A1 knockdown induced lipid accumulation through mammalian target of rapamycin complex 1 (mTORC1), but not mTORC2. Moreover, siRNA-mediated knockdown of NR6A1 increased expression of insulin receptor (INSR) and potentitated insulin-induced phosphorylation of mTOR and AKT partly via miR-205-5p in HepG2 cells.

Conclusions

These findings provide important new insights into the role of NR6A1 in the lipogenesis in HepG2 cells.

Graphical abstract

.

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0389-4) contains supplementary material, which is available to authorized users.

Positive expression of NR6A1/CT150 as a predictor of biochemical recurrence-free survival in prostate cancer patients

NR6A1/CT150, as an orphan receptor, is a novel member of the cancer-testis (CT) antigen family. Here, we investigated the expression and function of NR6A1 and its underlying mechanisms in prostate cancer (PCa) patients who underwent radical prostatectomy. A total of 303 cases of prostate cancer after radical prostatectomy were analysed in a tissue microarray (TMA) for NR6A1 immunohistochemistry-based protein expression. Kaplan–Meier/log-rank analysis and Cox regression analysis were used to investigate the relationship between NR6A1 expression and clinicopathological factors in PCa. NR6A1 mRNA expression was examined by reversing transcriptase-polymerase chain reaction (RT-PCR). Knockdown of NR6A1 by small interfering RNA mediated gene silencing and overexpression of NR6A1 through lentivirus were utilized to investigate its potential role in prostate cancer cells. NR6A1 protein expression was 29.7% (90/303) and mRNA expression was 28.1%(9/32) in PCa patients. NR6A1 expression was significantly associated with Gleason score (GS) (P=0.003) and tumor stage (P=0.042). The patients with positive NR6A1 expression have a shorter biochemical recurrence-free survival. NR6A1 predicted biochemical recurrence in univariate (P=0.0159) and multivariate models (P=0.0317). In addition, gene silencing of NR6A1 resulted in G0/G1 phase cell cycle arrest, and decreased metastatic and invasive potential of prostate cancer cells DU145 and PC3. In contrast, overexpression of NR6A1 reduced G0/G1 phase cell cycle arrest, and promoted metastatic and invasive potential of prostate cancer cells 22RV1. And overexpression of NR6A1 significantly promoted tumor growth in vivo. What's more, down regulation of NR6A1 could reverse epithelial-to-mesenchymal transition (EMT) process in DU145 and PC3 cell lines, and the overexpression could enhance EMT process in 22RV1 cell line. NR6A1 played a prominent role in migration and invasion of PCa cells, and it is indicated that NR6A1 may act as a novel marker for biochemical recurrence after radical prostatectomy.

Germ Cell Nuclear Factor (GCNF/RTR) Regulates Transcription of Gonadotropin-Regulated Testicular RNA Helicase (GRTH/DDX25) in Testicular Germ Cells--The Androgen Connection

Gonadotropin-regulated testicular RNA helicase (GRTH) (GRTH/DDX25), is a testis-specific protein essential for completion of spermatogenesis. Transgenic mice carrying 5'-flanking regions of the GRTH gene/green fluorescence protein (GFP) reporter revealed a region (-6.4/-3.6 kb) which directs its expression in germ cells (GCs) via androgen action. This study identifies a functional cis-binding element on the GRTH gene for GC nuclear factor (GCNF) (GCNF/RTR) required to regulate GRTH gene expression in postmeiotic testis GCs and explore the action of androgen on GCNF and GRTH transcription/expression. GCNF expression decreased in mice testis upon flutamide (androgen receptor antagonist) treatment, indicating the presence of an androgen/GCNF network to direct GRTH expression in GC. Binding studies and chromatin immunoprecipitation demonstrated specific association of GCNF to a consensus half-site (-5270/-5252) of the GRTH gene in both round spermatids and spermatocytes, which was abolished by flutamide treatment in round spermatids. Moreover, flutamide treatment of wild-type mice caused selective reduction of GCNF and GRTH in round spermatids. GCNF knock-down in seminiferous tubules from GRTH-transgenic mice (dark zone, round spermatid rich) caused decreased GFP expression. Exposure of tubules to flutamide caused decrease in GCNF and GFP expression, whereas androgen exposure induced significant increase. Our studies provide evidence for actions of androgen on GCNF cell-specific regulation of GRTH expression in GC. GRTH associates with GCNF mRNA, its absence caused increase on GCNF expression and mRNA stability indicative of a negative autocrine regulation of GCNF by GRTH. These in vivo/in vitro models link androgen actions to GC through GCNF, as regulated transfactor that controls transcription/expression of GRTH.

Germ cell nuclear factor regulates gametogenesis in developing gonads

Expression of germ cell nuclear factor (GCNF; Nr6a1), an orphan member of the nuclear receptor gene family of transcription factors, during gastrulation and neurulation is critical for normal embryogenesis in mice. Gcnf represses the expression of the POU-domain transcription factor Oct4 (Pou5f1) during mouse post-implantation development. Although Gcnf expression is not critical for the embryonic segregation of the germ cell lineage, we found that sexually dimorphic expression of Gcnf in germ cells correlates with the expression of pluripotency-associated genes, such as Oct4, Sox2, and Nanog, as well as the early meiotic marker gene Stra8. To elucidate the role of Gcnf during mouse germ cell differentiation, we generated an ex vivo Gcnf-knockdown model in combination with a regulated CreLox mutation of Gcnf. Lack of Gcnf impairs normal spermatogenesis and oogenesis in vivo, as well as the derivation of germ cells from embryonic stem cells (ESCs) in vitro. Inactivation of the Gcnf gene in vivo leads to loss of repression of Oct4 expression in both male and female gonads.

Revisiting the role of GCNF in embryonic development

GCNF (NR6A1) is essential for embryonic development. GCNF belongs to the nuclear receptor (NR) gene family, it is distantly related to other NRs and is the only member of subfamily 6. As the ligand for GCNF has not been identified, GCNF is designated an orphan nuclear receptor. GCNF has been found to be a transcriptional repressor, through specific binding to DR0 response elements, which is found in the Oct4 proximal promoter for example. GCNF is expressed widely in early mouse embryos, and later in the developing nervous system. GCNF knockout mouse embryos die around E10.5. GCNF is required for the restriction of Oct4 expression to primordial germ cells after gastrulation. GCNF is expressed in ES/EC cells and during their differentiation, and has been reported to be required for pluripotency gene repression during retinoic acid (RA)-induced mES cell differentiation. GCNF can interact with DNA methylation proteins, and is suggested to recruit DNA methylation complexes to repress and silence Oct4 expression. Nuclear receptor regulation in embryonic development is a complex process, as different nuclear receptors have overlapping and distinct functions. In-depth exploration of GCNF function and mechanism of action will help to comprehensively understand the nuclear receptor regulation in embryonic development.

Expression screening of cancer/testis genes in prostate cancer identifies NR6A1 as a novel marker of disease progression and aggressiveness

BACKGROUND

Cancer/Testis (CT) genes are expressed in male gonads, repressed in most healthy somatic tissues and de-repressed in various somatic malignancies including prostate cancers (PCa). Because of their specific expression signature and their associations with tumor aggressiveness and poor outcomes, CT genes are considered to be useful biomarkers and they are also targets for the development of new anti-cancer immunotherapies. The aim of this study was to identify novel CT genes associated with hormone-sensitive prostate cancer (HSPC), and castration-resistant prostate cancer (CRPC).

METHODS

To identify novel CT genes we screened genes for which transcripts were detected by RNA profiling specifically in normal testis and in either HSPC or CRPC as compared to normal prostate and 44 other healthy tissues using GeneChips. The expression and clinicopathological significance of a promising candidate--NR6A1--was examined in HSPC, CRPC, and metastatic site samples using tissue microarrays.

RESULTS

We report the identification of 98 genes detected in CRPC, HSPC and testicular samples but not in the normal controls. Among them, cellular levels of NR6A1 were found to be higher in HSPC compared to normal prostate and further increased in metastatic lesions and CRPC. Furthermore, increased NR6A1 immunoreactivity was significantly associated with a high Gleason score, advanced pT stage and cancer cell proliferation.

CONCLUSIONS

Our results show that cellular levels of NR6A1 are correlated with disease progression in PCa. We suggest that this essential orphan nuclear receptor is a potential therapeutic target as well as a biomarker of PCa aggressiveness.

Global human tissue profiling and protein network analysis reveals distinct levels of transcriptional germline-specificity and identifies target genes for male infertility

BACKGROUND

Mammalian spermatogenesis is a process that involves a complex expression program in both somatic and germ cells present in the male gonad. A number of studies have attempted to define the transcriptome of male meiosis and gametogenesis in rodents and primates. Few human transcripts, however, have been associated with testicular somatic cells and germ cells at different post-natal developmental stages and little is known about their level of germline-specificity compared with non-testicular tissues.

METHODS

We quantified human transcripts using GeneChips and a total of 47 biopsies from prepubertal children diagnosed with undescended testis, infertile adult patients whose spermatogenesis is arrested at consecutive stages and fertile control individuals. These results were integrated with data from enriched normal germ cells, non-testicular expression data, phenotype information, predicted regulatory DNA-binding motifs and interactome data.

RESULTS

Among 3580 genes for which we found differential transcript concentrations in somatic and germ cells present in human testis, 933 were undetectable in 45 embryonic and adult non-testicular tissues, including many that were corroborated at protein level by published gene annotation data and histological high-throughput protein immunodetection assays. Using motif enrichment analyses, we identified regulatory promoter elements likely involved in germline development. Finally, we constructed a regulatory disease network for human fertility by integrating expression signals, interactome information, phenotypes and functional annotation data.

CONCLUSIONS

Our results provide broad insight into the post-natal human testicular transcriptome at the level of cell populations and in a global somatic tissular context. Furthermore, they yield clues for genetic causes of male infertility and will facilitate the identification of novel cancer/testis genes as targets for cancer immunotherapies.

Embryonic stem cell markers

Embryonic stem cell (ESC) markers are molecules specifically expressed in ES cells. Understanding of the functions of these markers is critical for characterization and elucidation for the mechanism of ESC pluripotent maintenance and self-renewal, therefore helping to accelerate the clinical application of ES cells. Unfortunately, different cell types can share single or sometimes multiple markers; thus the main obstacle in the clinical application of ESC is to purify ES cells from other types of cells, especially tumor cells. Currently, the marker-based flow cytometry (FCM) technique and magnetic cell sorting (MACS) are the most effective cell isolating methods, and a detailed maker list will help to initially identify, as well as isolate ESCs using these methods. In the current review, we discuss a wide range of cell surface and generic molecular markers that are indicative of the undifferentiated ESCs. Other types of molecules, such as lectins and peptides, which bind to ESC via affinity and specificity, are also summarized. In addition, we review several markers that overlap with tumor stem cells (TSCs), which suggest that uncertainty still exists regarding the benefits of using these markers alone or in various combinations when identifying and isolating cells.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 4: intercellular bridges, mitochondria, nuclear envelope, apoptosis, ubiquitination, membrane/voltage-gated channels, methylation/acetylation, and transcription factors

As germ cells divide and differentiate from spermatogonia to spermatozoa, they share a number of structural and functional features that are common to all generations of germ cells and these features are discussed herein. Germ cells are linked to one another by large intercellular bridges which serve to move molecules and even large organelles from the cytoplasm of one cell to another. Mitochondria take on different shapes and features and topographical arrangements to accommodate their specific needs during spermatogenesis. The nuclear envelope and pore complex also undergo extensive modifications concomitant with the development of germ cell generations. Apoptosis is an event that is normally triggered by germ cells and involves many proteins. It occurs to limit the germ cell pool and acts as a quality control mechanism. The ubiquitin pathway comprises enzymes that ubiquitinate as well as deubiquitinate target proteins and this pathway is present and functional in germ cells. Germ cells express many proteins involved in water balance and pH control as well as voltage-gated ion channel movement. In the nucleus, proteins undergo epigenetic modifications which include methylation, acetylation, and phosphorylation, with each of these modifications signaling changes in chromatin structure. Germ cells contain specialized transcription complexes that coordinate the differentiation program of spermatogenesis, and there are many male germ cell-specific differences in the components of this machinery. All of the above features of germ cells will be discussed along with the specific proteins/genes and abnormalities to fertility related to each topic.

Functional cooperation between CREM and GCNF directs gene expression in haploid male germ cells

Cellular differentiation and development of germ cells critically depend on a coordinated activation and repression of specific genes. The underlying regulation mechanisms, however, still lack a lot of understanding. Here, we describe that both the testis-specific transcriptional activator CREMτ (cAMP response element modulator tau) and the repressor GCNF (germ cell nuclear factor) have an overlapping binding site which alone is sufficient to direct cell type-specific expression in vivo in a heterologous promoter context. Expression of the transgene driven by the CREM/GCNF site is detectable in spermatids, but not in any somatic tissue or at any other stages during germ cell differentiation. CREMτ acts as an activator of gene transcription whereas GCNF suppresses this activity. Both factors compete for binding to the same DNA response element. Effective binding of CREM and GCNF highly depends on composition and epigenetic modification of the binding site. We also discovered that CREM and GCNF bind to each other via their DNA binding domains, indicating a complex interaction between the two factors. There are several testis-specific target genes that are regulated by CREM and GCNF in a reciprocal manner, showing a similar activation pattern as during spermatogenesis. Our data indicate that a single common binding site for CREM and GCNF is sufficient to specifically direct gene transcription in a tissue-, cell type- and differentiation-specific manner.

Germ cell nuclear factor directly represses the transcription of peroxisome proliferator-activated receptor delta gene

Germ cell nuclear factor (GCNF) is a transcription factor that can repress gene transcription and plays an important role during spermatogenesis. Peroxisome proliferator-activated receptor delta (PPARdelta) is a nuclear hormone receptor belonging to the steroid receptor superfamily. It can activate the expression of many genes, including those involved in lipid metabolism. In this report, we showed that GCNF specifically interacts with PPARdelta promoter. Overexpression of GCNF in African green monkey SV40-transformed kidney fibroblast COS7 cells and mouse embryo fibroblast NIH 3T3 cells represses the activity of PPARdelta promoter. The mutation of GCNF response element in PPARdelta promoter relieves the repression in NIH 3T3 cells and mouse testis. Moreover, we showed that GCNF in nuclear extracts of mouse testis is able to bind to PPARdelta promoter directly. We also found that GCNF and PPARdelta mRNA were expressed with different patterns in mouse testis by in situ hybridization. These results suggested that GCNF might be a negative regulator of PPARdelta gene expression through its direct interaction with PPARdelta promoter in mouse testis.

0610009K11Rik, a testis-specific and germ cell nuclear receptor-interacting protein

Using an in silico approach, a putative nuclear receptor-interacting protein 0610009K11Rik was identified in mouse testis. We named this gene testis-specific nuclear receptor-interacting protein-1 (Tnrip-1). Tnrip-1 was predominantly expressed in the testis of adult mouse tissues. Expression of Tnrip-1 in the testis was regulated during postnatal development, with robust expression in 14-day-old or older testes. In situ hybridization analyses showed that Tnrip-1 is highly expressed in pachytene spermatocytes and spermatids. Consistent with its mRNA expression, Tnrip-1 protein was detected in adult mouse testes. Immunohistochemical studies showed that Tnrip-1 is a nuclear protein and mainly expressed in pachytene spermatocytes and round spermatids. Moreover, co-immunoprecipitation analyses showed that endogenous Tnrip-1 protein can interact with germ cell nuclear receptor (GCNF) in adult mouse testes. Our results suggest that Tnrip-1 is a testis-specific and GCNF-interacting protein which may be involved in the modulation of GCNF-mediated gene transcription in spermatogenic cells within the testis.

International Union of Pharmacology. LXVI. Orphan nuclear receptors

Half of the members of the nuclear receptors superfamily are so-called "orphan" receptors because the identity of their ligand, if any, is unknown. Because of their important biological roles, the study of orphan receptors has attracted much attention recently and has resulted in rapid advances that have helped in the discovery of novel signaling pathways. In this review we present the main features of orphan receptors, discuss the structure of their ligand-binding domains and their biological functions. The paradoxical existence of a pharmacology of orphan receptors, a rapidly growing and innovative field, is highlighted.

The transcription factor CREMtau and cAMP regulate promoter activity of the Na,K-ATPase alpha4 isoform

The Na,K-ATPase is an essential enzyme of the plasma membrane that plays a key role in numerous cell processes that depend on the transcellular gradients of Na(+) and K(+). Among the various isoforms of the catalytic subunit of the Na,K-ATPase, alpha4 exhibits the most limited pattern of expression, being restricted to male germ cells. Activity of alpha4 is essential for sperm function, and alpha4 is upregulated during spermatogenesis. The present study addressed the transcriptional control of the human Na,K-ATPase alpha4 gene, ATP1A4. We describe that a 5' untranslated region of the ATP1A4 gene (designated -339/+480 based on the ATP1A4 transcription initiation site) has promoter activity in luciferase reporter assays. Computer analysis of this promoter region revealed consensus sites (CRE) for the cyclic AMP (cAMP) response element modulator (CREM). Accordingly, dibutyryl cAMP (db-cAMP) and ectopic expression of CREMtau, a testis specific splice variant of CREM were able to activate the ATP1A4 promoter driven expression of luciferase in HEK 293 T, JEG-3 and GC-1 cells. Further characterization of the effect of db-cAMP and CREMtau on deleted constructs of the ATP1A4 promoter (-339/+80, and +25/+480), and on the -339/+480 region carrying mutations in the CRE sites showed that db-cAMP and CREMtau effect required the CRE motif located 263 bp upstream the transcription initiation site. EMSA experiments confirmed the CRE sequence as a bonafide CREMtau binding site. These results constitute the first demonstration of the transcriptional control of ATP1A4 gene expression by cAMP and by CREMtau, a transcription factor essential for male germ cell gene expression.

Germ cell nuclear factor is a repressor of CRIPTO-1 and CRIPTO-3

The pluripotency of embryonic stem and embryonic carcinoma cells is maintained by the expression of a set of "stemness" genes. Whereas these genes are down-regulated upon induction of differentiation, the germ cell nuclear factor (GCNF) is transiently up-regulated and represses several pluripotency genes. CRIPTO-1, a co-receptor for the morphogen nodal, is strongly expressed in undifferentiated cells and is rapidly down-regulated during retinoic acid-induced differentiation. Although CRIPTO-1 is expressed at very low levels in adult tissues under normal conditions, it is found highly expressed in a broad range of tumors, where it acts as a potent oncogene. We show that expression of CRIPTO-1 is directly repressed by GCNF during differentiation of the human teratocarcinoma cell line, NT2. GCNF bound to a DR0 element of the CRIPTO-1 promoter in vitro, as shown by electrophoretic mobility shift assays, and in vivo, as demonstrated by chromatin immunoprecipitation. Reporter gene assays demonstrated that GCNF-mediated repression of the CRIPTO-1 promoter is dependent upon the DR0 site. Overexpression of GCNF in NT2 cells resulted in repression of CRIPTO-1 transcription, whereas expression of the transcription-activating fusion construct GCNF-VP16 led to an induction of the CRIPTO-1 gene and prevented its retinoic acid-induced down-regulation. Furthermore, we demonstrated that CRIPTO-3, a processed pseudogene of CRIPTO-1 on the X chromosome, is expressed in undifferentiated NT2 cells and is regulated by GCNF in parallel to CRIPTO-1. Thus, our study supports the hypothesis of GCNF playing a central role during differentiation of stem cells by repression of stem cell-specific genes.

K-SPMM: a database of murine spermatogenic promoters modules & motifs

Background

Understanding the regulatory processes that coordinate the cascade of gene expression leading to male gamete development has proven challenging. Research has been hindered in part by an incomplete picture of the regulatory elements that are both characteristic of and distinctive to the broad population of spermatogenically expressed genes.

Description

K-SPMM, a database of murine Spermatogenic Promoters Modules and Motifs, has been developed as a web-based resource for the comparative analysis of promoter regions and their constituent elements in developing male germ cells. The system contains data on 7,551 genes and 11,715 putative promoter regions in Sertoli cells, spermatogonia, spermatocytes and spermatids. K-SPMM provides a detailed portrait of promoter site components, ranging from broad distributions of transcription factor binding sites to graphical illustrations of dimeric modules with respect to individual transcription start sites. Binding sites are identified through their similarities to position weight matrices catalogued in either the JASPAR or the TRANSFAC transcription factor archives. A flexible search function allows sub-populations of promoters to be identified on the basis of their presence in any of the four cell-types, their association with a list of genes or their component transcription-factor families.

Conclusion

This system can now be used independently or in conjunction with other databases of gene expression as a powerful aid to research networks of co-regulation. We illustrate this with respect to the spermiogenically active protamine locus in which binding sites are predicted that align well with biologically foot-printed protein binding domains.

Availability

PSPC1, NONO, and SFPQ are expressed in mouse Sertoli cells and may function as coregulators of androgen receptor-mediated transcription

In Sertoli cells of testis, androgen receptor-regulated gene transcription plays an indispensable role in maintaining spermatogenesis. Androgen receptor activity is modulated by a number of coregulators which are associated with the androgen receptor. Non-POU-domain-containing, octamer binding protein (NONO), a member of the DBHS-containing proteins, complexes with androgen receptor and functions as a coactivator for the receptor. Paraspeckle protein 1 alpha isoform (PSPC1, previously known as PSP1) and Splicing factor, proline- and glutamine-rich (SFPQ, previously known as PSF), other members of the DBHS-containing proteins, are also found in androgen receptor complexes, suggesting that these DBHS-containing proteins may cooperatively regulate androgen receptor-mediated gene transcription. We demonstrated that PSPC1, NONO, and SFPQ are coexpressed in Sertoli cell line TTE3 and interact reciprocally. The effect of the DBHS-containing proteins on the transcriptional activity was assessed using the construct containing androgen-responsive elements followed by a luciferase gene. The results showed that all the DBHS-containing proteins activate androgen receptor-mediated transcription, and PSPC1 is the most effective coactivator among them. Furthermore, we confirmed the presence of PSPC1, NONO, and SFPQ proteins in Sertoli cells of adult mouse testis sections. These observations suggest that PSPC1, NONO, and SFPQ form complexes with each other in Sertoli cells and may regulate androgen receptor-mediated transcriptional activity.

Protamines and male infertility

Protamines are the major nuclear sperm proteins. The human sperm nucleus contains two types of protamine: protamine 1 (P1) encoded by a single-copy gene and the family of protamine 2 (P2) proteins (P2, P3 and P4), all also encoded by a single gene that is transcribed and translated into a precursor protein. The protamines were discovered more than a century ago, but their function is not yet fully understood. In fact, different hypotheses have been proposed: condensation of the sperm nucleus into a compact hydrodynamic shape, protection of the genetic message delivered by the spermatozoa, involvement in the processes maintaining the integrity and repair of DNA during or after the nucleohistone-nucleoprotamine transition and involvement in the epigenetic imprinting of the spermatozoa. Protamines are also one of the most variable proteins found in nature, with data supporting a positive Darwinian selection. Changes in the expression of P1 and P2 protamines have been found to be associated with infertility in man. Mutations in the protamine genes have also been found in some infertile patients. Transgenic mice defective in the expression of protamines also present several structural defects in the sperm nucleus and have variable degrees of infertility. There is also evidence that altered levels of protamines may result in an increased susceptibility to injury in the spermatozoan DNA causing infertility or poor outcomes in assisted reproduction. The present work reviews the articles published to date on the relationship between protamines and infertility.