Loss of protein phosphatase 1c{gamma} (PPP1CC) leads to impaired spermatogenesis associated with defects in chromatin condensation and acrosome development: an ultrastructural analysis

Target silencing of porcine SPAG6 and PPP1CC by shRNA attenuated sperm motility

The quality of sperm significantly influences the reproductive efficiency of pig herds. High-quality sperm is necessary for efficient fertilization and to maximize the litter numbers in commercial pig farming. However, the understanding of genes regulating porcine sperm motility and viability is limited. In this study, we validated porcine sperm/Sertoli-specific promoters through the luciferase reporter system and identified vital genes for sperm quality via loss-of-function means. Further, the shRNAs driven by the ACE and SP-10 promoters were used to knockdown the SPAG6 and PPP1CC genes which were provisionally important for sperm quality. We assessed the effects of SPAG6 and PPP1CC knockdown on sperm motility by using the sperm quality analyzer and flow cytometry. The results showed that the ACE promoter is active in both porcine Sertoli cells and sperms, whereas the SP-10 promoter is operating exclusively in sperm cells. Targeted interference with SPAG6 and PPP1CC expression in sperm cells decreases the motility and increases apoptosis rates in porcine sperms. These findings not only offer new genetic tools for targeting male germ cells but also highlight the crucial roles of SPAG6 and PPP1CC in porcine sperm function.

Proteomic analysis reveals the potential positive effects of Mito-TEMPO on ram sperm motility and fertility during cryopreservation

The aim of this study was to investigate the effects of mitochondria-targeted antioxidant Mito-TEMPO on the protein profile of ram sperm during cryopreservation and evaluate the cryoprotective roles of Mito-TEMPO on ram sperm quality and fertilization capacity. Semen collected from 8 Dorper rams was cryopreserved in TCG-egg yolk extender supplemented with various concentrations of Mito-TEMPO (0, 20, 40 and 60 μM). After thawing, sperm characteristics, antioxidant status and the abundance of hexose transporters (GLUT 3 and 8) were analyzed. The cervical artificial insemination (AI) was performed to evaluate the fertilization ability of cryopreserved ram sperm. The alterations of sperm proteomic profile between the control and MT₄₀ groups were determined using iTRAQ-coupled LC-MS. Supplementation with 40 μM of Mito-TEMPO resulted in the highest post-thaw sperm motility and kinematics. Sperm quality, antioxidant capacity and glucose transporter abundance of frozen-thawed ram sperm were elevated in the MT₄₀ group. The inclusion of 40 μM Mito-TEMPO in freezing extender also resulted in the higher pregnancy rate of ewes. A total of 457 proteins including 179 upregulated proteins and 278 downregulated proteins were defied as differentially expressed proteins (DEPs) using fold change (FC) > 1.2 with P < 0.05. Sixty-one DEPs with (FC > 1.5) were dramatically regulated by Mito-TEMPO. These DEPs are mainly involved in sperm motility, energy metabolism and capacitation. Our data suggest that the beneficial effects of Mito-TEMPO on sperm motility and fertility potential of cryopreserved ram semen are achieved by regulating sperm antioxidant capacity and sperm proteins related to energy metabolism and fertility.

Role of testis‑specific serine kinase 1B in undiagnosed male infertility

Male infertility is a global problem affecting a considerable part of the male population. Current guidelines and practices aimed at diagnosing the cause of this problem still have low diagnostic yield. As novel candidate genes for infertility emerge, their functional role needs to be investigated in patient populations. The present study aimed to investigate testis-specific serine kinase 1B (TSSK1B), which was discovered in a previously diagnosed patient. Sanger sequencing of the coding regions and exon borders of TSSK1B was performed in a cohort of 100 male Bulgarian patients with unresolved infertility causes. Missense mutations were discovered in 10% of patients and were associated with clinical data on sperm dysmorphology. Two previously unreported mutations were discovered, p.3D>N and p.52F>L. All mutations were scored via in silico predictors and protein modelling using AlphaFold2. The present findings indicated an association between TSSK1B mutations and asthenoteratozoospermia, with further missense mutations in patients with azoospermia and teratozoospermia. Mutations in TSSK1B may be a cause of undiagnosed cases of male infertility and should be considered when molecular diagnostics are warranted.

Autophagy: a multifaceted player in the fate of sperm

BACKGROUND

Autophagy is an intracellular catabolic process of degrading and recycling proteins and organelles to modulate various physiological and pathological events, including cell differentiation and development. Emerging data indicate that autophagy is closely associated with male reproduction, especially the biosynthetic and catabolic processes of sperm. Throughout the fate of sperm, a series of highly specialized cellular events occur, involving pre-testicular, testicular and post-testicular events. Nonetheless, the most fundamental question of whether autophagy plays a protective or harmful role in male reproduction, especially in sperm, remains unclear.

OBJECTIVE AND RATIONALE

We summarize the functional roles of autophagy in the pre-testicular (hypothalamic–pituitary–testis (HPG) axis), testicular (spermatocytogenesis, spermatidogenesis, spermiogenesis, spermiation) and post-testicular (sperm maturation and fertilization) processes according to the timeline of sperm fate. Additionally, critical mechanisms of the action and clinical impacts of autophagy on sperm are identified, laying the foundation for the treatment of male infertility.

SEARCH METHODS

In this narrative review, the PubMed database was used to search peer-reviewed publications for summarizing the functional roles of autophagy in the fate of sperm using the following terms: ‘autophagy’, ‘sperm’, ‘hypothalamic–pituitary–testis axis’, ‘spermatogenesis’, ‘spermatocytogenesis’, ‘spermatidogenesis’, ‘spermiogenesis’, ‘spermiation’, ‘sperm maturation’, ‘fertilization’, ‘capacitation’ and ‘acrosome’ in combination with autophagy-related proteins. We also performed a bibliographic search for the clinical impact of the autophagy process using the keywords of autophagy inhibitors such as ‘bafilomycin A1’, ‘chloroquine’, ‘hydroxychloroquine’, ‘3-Methyl Adenine (3-MA)’, ‘lucanthone’, ‘wortmannin’ and autophagy activators such as ‘rapamycin’, ‘perifosine’, ‘metformin’ in combination with ‘disease’, ‘treatment’, ‘therapy’, ‘male infertility’ and equivalent terms. In addition, reference lists of primary and review articles were reviewed for additional relevant publications. All relevant publications until August 2021 were critically evaluated and discussed on the basis of relevance, quality and timelines.

OUTCOMES

(i) In pre-testicular processes, autophagy-related genes are involved in the regulation of the HPG axis; and (ii) in testicular processes, mTORC1, the main gate to autophagy, is crucial for spermatogonia stem cell (SCCs) proliferation, differentiation, meiotic progression, inactivation of sex chromosomes and spermiogenesis. During spermatidogenesis, autophagy maintains haploid round spermatid chromatoid body homeostasis for differentiation. During spermiogenesis, autophagy participates in acrosome biogenesis, flagella assembly, head shaping and the removal of cytoplasm from elongating spermatid. After spermatogenesis, through PDLIM1, autophagy orchestrates apical ectoplasmic specialization and basal ectoplasmic specialization to handle cytoskeleton assembly, governing spermatid movement and release during spermiation. In post-testicular processes, there is no direct evidence that autophagy participates in the process of capacitation. However, autophagy modulates the acrosome reaction, paternal mitochondria elimination and clearance of membranous organelles during fertilization.

WIDER IMPLICATIONS

Deciphering the roles of autophagy in the entire fate of sperm will provide valuable insights into therapies for diseases, especially male infertility.

Evaluation of seminal plasma HSPA2 protein as a biomarker of human spermatogenesis status

In mammals, testicular Heat shock-related 70 kDa protein 2 (HSPA2) is a chaperon strictly linked to spermatogenesis status, whereas its presence in spermatozoa ensures successful oocyte fertilization. However, there is little information on this protein in seminal plasma in infertile males. Based on our previous two independent studies, we have selected HSPA2 to evaluate this seminal plasma protein is a potential biomarker of correct spermatogenesis. Using immunoblotting and mass spectrometry (MS) we have screened human seminal plasma samples for the presence of HSPA2. Samples were obtained from individuals with normozoospermia, cryptozoospermia, non-obstructive and obstructive azoospermia. Our results showed a lack of HSPA2 in seminal plasma in all azoospermic males however, in cryptozoospermia the results were extremely diversified. Additionally, the application of 2-dimensional gel electrophoresis (2-DE) indicated the presence of additional protein isoforms suggesting possible mechanisms underlying the male infertility. Our findings suggest seminal plasma HSPA2 protein as a possible biomarker not only of spermatogenesis status, especially in cryptozoospermic males, but also as a biomarker predicting the success of reproductive treatment including assisted reproductive techniques (ART).

Dependence of sperm structural and functional integrity on testicular calcineurin isoform PPP3R2 expression

After leaving the testis, mammalian sperm undergo a sequential maturation process in the epididymis followed by capacitation during their movement through the female reproductive tract. These phenotypic changes are associated with modification of protein phosphorylation and membrane remodeling, which is requisite for sperm to acquire forward motility and induce fertilization. However, the molecular mechanisms underlying sperm maturation and capacitation are still not fully understood. Herein, we show that PPP3R2, a testis-specific regulatory subunit of protein phosphatase 3 (an isoform of calcineurin in the testis), is essential for sperm maturation and capacitation. Knockout of Ppp3r2 in mice leads to male sterility due to sperm motility impairment and morphological defects. One very noteworthy change includes increases in sperm membrane stiffness. Moreover, PPP3R2 regulates sperm maturation and capacitation via (i) modulation of membrane diffusion barrier function at the annulus and (ii) facilitation of cholesterol efflux during sperm capacitation. Taken together, PPP3R2 plays a critical role in modulating cholesterol efflux and mediating the dynamic control of membrane remodeling during sperm maturation and capacitation.

The protein phosphatase isoform PP1γ1 substitutes for PP1γ2 to support spermatogenesis but not normal sperm function and fertility†

Four isoforms of serine/threonine phosphatase type I, PP1α, PP1β, PP1γ1, and PP1γ2, are derived from three genes. The PP1γ1 and PP1γ2 isoforms are alternately spliced transcripts of the protein phosphatase 1 catalytic subunit gamma gene (Ppp1cc). While PP1γ1 is ubiquitous in somatic cells, PP1γ2 is expressed exclusively in testicular germ cells and sperm. Ppp1cc knockout male mice (-/-), lacking both PP1γ1 and PP1γ2, are sterile due to impaired sperm morphogenesis. Fertility and normal sperm function can be restored by transgenic expression of PP1γ2 alone in testis of Ppp1cc (-/-) mice. The purpose of this study was to determine whether the PP1γ1 isoform is functionally equivalent to PP1γ2 in supporting spermatogenesis and male fertility. Significant levels of transgenic PP1γ1 expression occurred only when the transgene lacked a 1-kb 3΄UTR region immediately following the stop codon of the PP1γ1 transcript. PP1γ1 was also incorporated into sperm at levels comparable to PP1γ2 in sperm from wild-type mice. Spermatogenesis was restored in mice expressing PP1γ1 in the absence of PP1γ2. However, males from the transgenic rescue lines were subfertile. Sperm from the PP1γ1 rescue mice were unable to fertilize eggs in vitro. Intrasperm localization of PP1γ1 and the association of the protein regulators of the phosphatase were altered in epididymal sperm in transgenic PP1γ1 compared to PP1γ2. Thus, the ubiquitous isoform PP1γ1, not normally expressed in differentiating germ cells, could replace PP1γ2 to support spermatogenesis and spermiation. However, PP1γ2, which is the PP1 isoform in mammalian sperm, has an isoform-specific role in supporting normal sperm function and fertility.

Functions and therapeutic potential of protein phosphatase 1: Insights from mouse genetics

Protein phosphatase 1 (PP1) catalyzes more than half of all phosphoserine/threonine dephosphorylation reactions in mammalian cells. In vivo PP1 does not exist as a free catalytic subunit but is always associated with at least one regulatory PP1-interacting protein (PIP) to generate a large set of distinct holoenzymes. Each PP1 complex controls the dephosphorylation of only a small subset of PP1 substrates. We screened the literature for genetically engineered mouse models and identified models for all PP1 isoforms and 104 PIPs. PP1 itself and at least 49 PIPs were connected to human disease-associated phenotypes. Additionally, phenotypes related to 17 PIPs were clearly linked to altered PP1 function, while such information was lacking for 32 other PIPs. We propose structural reverse genetics, which combines structural characterization of proteins with mouse genetics, to identify new PP1-related therapeutic targets. The available mouse models confirm the pleiotropic action of PP1 in health and diseases.

The protein phosphatase 1 regulator NIPP1 is essential for mammalian spermatogenesis

NIPP1 is one of the major nuclear interactors of protein phosphatase PP1. The deletion of NIPP1 in mice is early embryonic lethal, which has precluded functional studies in adult tissues. Hence, we have generated an inducible NIPP1 knockout model using a tamoxifen-inducible Cre recombinase transgene. The inactivation of the NIPP1 encoding alleles (Ppp1r8) in adult mice occurred very efficiently in testis and resulted in a gradual loss of germ cells, culminating in a Sertoli-cell only phenotype. Before the overt development of this phenotype Ppp1r8^−/− testis showed a decreased proliferation and survival capacity of cells of the spermatogenic lineage. A reduced proliferation was also detected after the tamoxifen-induced removal of NIPP1 from cultured testis slices and isolated germ cells enriched for undifferentiated spermatogonia, hinting at a testis-intrinsic defect. Consistent with the observed phenotype, RNA sequencing identified changes in the transcript levels of cell-cycle and apoptosis regulating genes in NIPP1-depleted testis. We conclude that NIPP1 is essential for mammalian spermatogenesis because it is indispensable for the proliferation and survival of progenitor germ cells, including (un)differentiated spermatogonia.

Characterisation of several ankyrin repeat protein variant 2, a phosphoprotein phosphatase 1-interacting protein, in testis and spermatozoa

Phosphoprotein phosphatase 1 (PPP1) catalytic subunit gamma 2 (PPP1CC2), a PPP1 isoform, is largely restricted to testicular germ cells and spermatozoa. The key to understanding PPP1 regulation in male germ cells lies in the identification and characterisation of its interacting partners. This study was undertaken to determine the expression patterns of the several ankyrin repeat protein variant 2 (SARP2), a PPP1-interacting protein, in testis and spermatozoa. SARP2 was found to be highly expressed in testis and spermatozoa, and its interaction with human spermatozoa endogenous PPP1CC2 was confirmed by immunoprecipitation. Expression analysis by RT-qPCR revealed that SARP2 and PPP1CC2 mRNA levels were significantly higher in the spermatocyte fraction. However, microscopy revealed that SARP2 protein was only present in the nucleus of elongating and mature spermatids and in spermatozoa. In spermatozoa, SARP2 was prominently expressed in the connecting piece and flagellum, as well as, to a lesser extent, in the acrosome. A yeast two-hybrid approach was used to detect SARP2-interacting proteins and a relevant interaction with a novel sperm-associated antigen 9 (SPAG9) variant, a testis and spermatozoa-specific c-Jun N-terminal kinase-binding protein, was validated in human spermatozoa. Given the expression pattern of SARP2 and its association with PPP1CC2 and SPAG9, it may play a role in spermiogenesis and sperm function, namely in sperm motility and the acrosome reaction.

Expression, function, and regulation of the testis-enriched heat shock HSPA2 gene in rodents and humans

The HSPA2 gene is a poorly characterized member of the HSPA (HSP70) family. HSPA2 was originally described as testis-specific and expressed at the highest level in pachytene spermatocytes of rodents, the expression of which is not induced by heat shock. HSPA2 is crucial for male fertility. However, recent advances have shown that HSPA2 is expressed in various tumors and in certain types of somatic tissues. In this review, we summarize the current knowledge on the HSPA2 expression pattern, including information on transcriptional, translational, posttranslational, and epigenetic mechanisms which regulate HSPA2 expression. We also present and discuss the current views concerning the functions of the HSPA2 protein in spermatogenetic, somatic, and cancer cells. The knowledge of the properties of HSPA2, although limited, shows this protein as a unique member of the HSPA family. However, understanding whether this protein could become a relevant cancer biomarker or a therapeutically applicable target requires extensive further studies.

TMEM225: a possible protein phosphatase 1γ2 (PP1γ2) regulator localizes to the equatorial segment in mouse spermatozoa

Tmem225 encodes a putative four-transmembrane domain protein that has an RVxF motif, which is known to be a consensus site for interacting with serine/threonine protein phosphatase 1 (PP1). We previously identified Tmem225 as one of 53 spermatogenesis-associated transmembrane protein genes, with no known physiological function. In this study, we investigated the expression and molecular characteristics of TMEM225 in mice. Tmem225 production was found to be specific to testicular germ cells, with expression increasing during spermatogenesis. In mature spermatozoa, TMEM225 is localized to the equatorial segment of the acrosome but not to the midpiece or tail. TMEM225 appears to be an outer and/or inner acrosomal membrane protein that is lost from the dorsal region of the acrosome after the acrosome reaction. TMEM225 interacts with PP1 in vivo, and a pull-down assay revealed that the carboxy-terminal region of TMEM225 can bind to PP1γ2, the predominant isoform of PP1 in male germ cells. In addition, TMEM225 inhibited PP1γ2 activity in vitro via its RVxF motif. Our results suggest that in mice, TMEM225 is involved in the differentiation and function of spermatozoa through the regulation of PP1γ2 activity, which is necessary for normal spermatogenesis as well as spermatozoa capacitation and motility.

A mutation study of sperm head shape and motility in the mouse: lessons for the clinic

Mouse mutants that show effects on sperm head shape, the sperm tail (flagellum), and motility were analysed in a systematic way. This was achieved by grouping mutations in the following classes: manchette, acrosome, Sertoli cell contact, chromatin remodelling, and mutations involved in complex regulations such as protein (de)phosphorylation and RNA stability, and flagellum/motility mutations. For all mutant phenotypes, flagellum function (motility) was affected. Head shape, including the nucleus, was also affected in spermatozoa of most mouse models, though with considerable variation. For the mutants that were categorized in the flagellum/motility group, generally normal head shapes were found, even when the flagellum did not develop or only poorly so. Most mutants are sterile, an occasional one semi-sterile. For completeness, the influence of the sex chromosomes on sperm phenotype is included. Functionally, the genes involved can be categorized as regulators of spermiogenesis. When extrapolating these data to human sperm samples, in vivo selection for motility would be the tool for weeding out the products of suboptimal spermiogenesis and epididymal sperm maturation. The striking dependency of motility on proper sperm head development is not easy to understand, but likely is of evolutionary benefit. Also, sperm competition after mating can never act against the long-term multi-generation interest of genetic integrity. Hence, it is plausible to suggest that short-term haplophase fitness i.e., motility, is developmentally integrated with proper nucleus maturation, including genetic integrity to protect multi-generation fitness. We hypothesize that, when the prime defect is in flagellum formation, apparently a feedback loop was not necessary as head morphogenesis in these mutants is mostly normal. Extrapolating to human-assisted reproductive techniques practice, this analysis would supply the arguments for the development of tools to select for motility as a continuous (non-discrete) parameter.

Protein phosphatase 1 catalytic isoforms: specificity toward interacting proteins

The coordinated and reciprocal action of serine-threonine protein kinases and protein phosphatases produces transitory phosphorylation, a fundamental regulatory mechanism for many biological processes. Phosphoprotein phosphatase 1 (PPP1), a major serine-threonine phosphatase, in particular, is ubiquitously distributed and regulates a broad range of cellular functions, including glycogen metabolism, cell cycle progression, and muscle relaxation. PPP1 has evolved effective catalytic machinery but in vitro lacks substrate specificity. In vivo, its specificity is achieved not only by the existence of different PPP1 catalytic isoforms, but also by binding of the catalytic moiety to a large number of regulatory or targeting subunits. Here, we will address exhaustively the existence of diverse PPP1 catalytic isoforms and the relevance of their specific partners and consequent functions.

CHD5 is required for spermiogenesis and chromatin condensation

Haploid spermatids undergo extensive cellular, molecular and morphological changes to form spermatozoa during spermiogenesis. Abnormalities in these steps can lead to serious male fertility problems, from oligospermia to complete azoospermia. CHD5 is a chromatin-remodeling nuclear protein expressed almost exclusively in the brain and testis. Male Chd5 knockout (KO) mice have deregulated spermatogenesis, characterized by immature sloughing of spermatids, spermiation failure, disorganization of the spermatogenic cycle and abnormal head morphology in elongating spermatids. This results in the inappropriate placement and juxtaposition of germ cell types within the epithelium. Sperm that did enter the epididymis displayed irregular shaped sperm heads, and retained cytoplasmic components. These sperm also stained positively for acidic aniline, indicating improper removal of histones and lack of proper chromatin condensation. Electron microscopy showed that spermatids in the seminiferous tubules of Chd5 KO mice have extensive nuclear deformation, with irregular shaped heads of elongated spermatids, and lack the progression of chromatin condensation in an anterior-to-posterior direction. However, the mRNA expression levels of other important genes controlling spermatogenesis were not affected. Chd5 KO mice also showed decreased H4 hyperacetylation beginning at stage IX, step 9, which is vital for the histone-transition protein replacement in spermiogenesis. Our data indicate that CHD5 is required for normal spermiogenesis, especially for spermatid chromatin condensation.

PPP1CC2 can form a kinase/phosphatase complex with the testis-specific proteins TSSK1 and TSKS in the mouse testis

The mouse protein phosphatase gene Ppp1cc is essential for male fertility, with mutants displaying a failure in spermatogenesis including a widespread loss of post-meiotic germ cells and abnormalities in the mitochondrial sheath. This phenotype is hypothesized to be responsible for the loss of the testis-specific isoform PPP1CC2. To identify PPP1CC2-interacting proteins with a function in spermatogenesis, we carried out GST pull-down assays in mouse testis lysates. Amongst the identified candidate interactors was the testis-specific protein kinase TSSK1, which is also essential for male fertility. Subsequent interaction experiments confirmed the capability of PPP1CC2 to form a complex with TSSK1 mediated by the direct interaction of each with the kinase substrate protein TSKS. Interaction between PPP1CC2 and TSKS is mediated through an RVxF docking motif on the TSKS surface. Phosphoproteomic analysis of the mouse testis identified a novel serine phosphorylation site within the TSKS RVxF motif that appears to negatively regulate binding to PPP1CC2. Immunohistochemical analysis of TSSK1 and TSKS in the Ppp1cc mutant testis showed reduced accumulation to distinct cytoplasmic foci and other abnormalities in their distribution consistent with the loss of germ cells and seminiferous tubule disorganization observed in the Ppp1cc mutant phenotype. A comparison of Ppp1cc and Tssk1/2 knockout phenotypes via electron microscopy revealed similar abnormalities in the morphology of the mitochondrial sheath. These data demonstrate a novel kinase/phosphatase complex in the testis that could play a critical role in the completion of spermatogenesis.

Spermatogonial stem cells alone are not sufficient to re-initiate spermatogenesis in the rat testis following adjudin-induced infertility

The blood-testis barrier (BTB) is a unique ultrastructure in the testis, which creates a specialized microenvironment in the seminiferous epithelium known as the apical (or adluminal) compartment for post-meiotic germ-cell development and for maintenance of an immunological barrier. In this study, we have demonstrated unequivocally that a functional and intact BTB is crucial for the initiation of spermatogenesis, in particular, the differentiation of spermatogonial stem cells (SSCs). It was shown that adult rats (∼300 g body weight, b.w.) treated with adjudin at 50 (low-dose) or 250 (high-dose) mg/kg b.w. by gavage led to germ-cell depletion from the seminiferous tubules and that >98% of the tubules were devoid of germ cells by ∼2 week and rats became infertile in both groups after the sperm reserve in the epididymis was exhausted. While the population of SSC/spermatogonia in the seminiferous tubules from both groups was similar to that of normal rats, only rats from the low-dose group were capable of re-initiating spermatogenesis; and by 20 weeks, greater than 75% of the tubules displayed normal spermatogenesis and the fertility of these rats rebounded. Detailed analysis by dual-labelled immunofluorescence analysis and a functional BTB integrity assay revealed that in both treatment groups, the BTB was disrupted from week 6 to week 12. However, the disrupted BTB 'resealed' in the low-dose group, but not in the high-dose group. Our findings illustrate that SSC/spermatogonia failed to differentiate into spermatocytes beyond A(aligned) spermatogonia in the high-dose group with a disrupted BTB. In short, these findings illustrate the critical significance of the BTB for re-initiation of spermatogenesis besides SSC and spermatogonia.

New candidate targets of protein phosphatase-1c-gamma-2 in mouse testis revealed by a differential phosphoproteome analysis

Reversible phosphorylation has been implicated in many developmental processes. Dephosphorylation is mediated by several families of phosphatases, including type 1 serine/threonine phosphatases (protein phosphatase-1 or PP1). The loss of the murine Ppp1cc gene causes male infertility as a result of impaired spermatogenesis. Ppp1cc encodes two splice isoforms, PPP1CC1 and PPP1CC2, with the latter being the most abundant isoform in the testis. However, the details of PPP1CC2's involvement in spermatogenesis are still unknown. As a phosphatase has been removed from the mutant mouse, a search for hyperphosphorylated proteins in the mutant testis may reveal the direct downstream targets of PPP1CC2. Using a whole tissue proteomics approach to identify testis-specific dephosphorylation targets of PPP1CC2, we found that two-dimensional electrophoresis identified 10 potential targets in the Ppp1cc null testis several of which are factors known to be important for spermatogenesis, such as HSPA2. Another potential target, tubulin, was found to be misregulated during Ppp1cc(-/-) spermatogenesis, disrupting manchette development. This work represents the first survey of the testicular phosphoproteome under pathological conditions.