Spermiogenesis Is Impaired in Mice Bearing a Targeted Mutation in the Protein Phosphatase 1cγ Gene

Varmuza, Susannah; Jurisicova, Andrea; Okano, Kazuhiro; Hudson, John W.; Boekelheide, Kim; Shipp, Elizabeth B.

doi:10.1006/dbio.1998.9100

Cited by 138 publications

(153 citation statements)

References 37 publications

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“…sions and spermiogenesis, as demonstrated by the knockout mouse model (Varmuza et al, 1999). Our demonstration that Sam68 is capable of shuttling between nuclear RNPs and polysomes may help explain some of the effects attributed to Sam68 on the cytoplasmic utilization of target mRNAs.…”

Section: Sam68 Associates With the Translational Machinerymentioning

confidence: 70%

“…Serine-threonine phosphatase involved in several cellular functions (i.e., cell cycle regulation, apoptosis) PP1-gammaϪ/Ϫ male mice are infertile (meiotic defects, impaired spermiogenesis; Varmuza et al, 1999). Glycerol kinase 2 (GyK2) BC061147…”

Section: Discussionmentioning

confidence: 99%

“…Direct sequencing of the clones obtained revealed five potential target mRNAs of Sam68 (Table 1). Interestingly, two of these targets encode proteins that play a crucial role in mouse spermatogenesis: the RNA-binding protein TENR and the protein phosphatase PP1-gamma (Varmuza et al, 1999;Connolly et al, 2005). A third target, Centrin-1, is a testis-specific isoform of Centrin, a centrosomal protein which is required for formation of motile apparatus of spermatids in Marsilea vestita and whose expression is regulated at the translational level during gametogenesis (Klink and Wolniak, 2001).…”

Section: Identification Of the Mrnas That Are Targets Of Sam68 In Primentioning

confidence: 99%

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The Nuclear RNA-binding Protein Sam68 Translocates to the Cytoplasm and Associates with the Polysomes in Mouse Spermatocytes

Paronetto

Zalfa

Botti

et al. 2006

MBoC

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Translational control plays a crucial role during gametogenesis in organisms as different as worms and mammals. Mouse knockout models have highlighted the essential function of many RNA-binding proteins during spermatogenesis. Herein we have investigated the expression and function during mammalian male meiosis of Sam68, an RNA-binding protein implicated in several aspects of RNA metabolism. Sam68 expression and localization within the cells is stage specific: it is expressed in the nucleus of spermatogonia, it disappears at the onset of meiosis (leptotene/zygotene stages), and it accumulates again in the nucleus of pachytene spermatocytes and round spermatids. During the meiotic divisions, Sam68 translocates to the cytoplasm where it is found associated with the polysomes. Translocation correlates with serine/ threonine phosphorylation and it is blocked by inhibitors of the mitogen activated protein kinases ERK1/2 and of the maturation promoting factor cyclinB-cdc2 complex. Both kinases associate with Sam68 in pachytene spermatocytes and phosphorylate the regulatory regions upstream and downstream of the Sam68 RNA-binding motif. Molecular cloning of the mRNAs associated with Sam68 in mouse spermatocytes reveals a subset of genes that might be posttranscriptionally regulated by this RNA-binding protein during spermatogenesis. We also demonstrate that Sam68 shuttles between the nucleus and the cytoplasm in secondary spermatocytes, suggesting that it may promote translation of specific RNA targets during the meiotic divisions.

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Section: Sam68 Associates With the Translational Machinerymentioning

confidence: 70%

Section: Discussionmentioning

confidence: 99%

Section: Identification Of the Mrnas That Are Targets Of Sam68 In Primentioning

confidence: 99%

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The Nuclear RNA-binding Protein Sam68 Translocates to the Cytoplasm and Associates with the Polysomes in Mouse Spermatocytes

Paronetto

Zalfa

Botti

et al. 2006

MBoC

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“…In particular, PP1γ2 is expressed mainly in the testis and is also present in spermatozoa, although the other isoforms are ubiquitously distributed [28,29]. Moreover, PP1 is likely involved in regulation of the production, maturation, flagellar movement and acrosome reaction of mammalian spermatozoa [30][31][32][33]. However, the biological significance of PP1 function is poorly understood in sperm flagella during expression of fertilizing ability in the female reproductive tract.…”

mentioning

confidence: 99%

Calyculin A-Sensitive Protein Phosphatases are Involved in Maintenance of Progressive Movement in Mouse Spermatozoa In Vitro by Suppression of Autophosphorylation of Protein Kinase A

Goto

Harayama

2009

J. Reprod. Dev.

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Abstract. Protein serine/threonine phosphorylation in mammalian sperm flagella has been considered to play important roles in regulation of motility. Protein phosphorylation state reflects balance of enzymatic activities between protein phosphatases and protein kinases [predominantly protein kinase A (PKA)]. The aims of this study were to disclose roles of protein phosphatases in the regulation of sperm motility and to provide evidence for suppression of PKA full activation by protein phosphatases in sperm flagella. Mouse epididymal spermatozoa were incubated with a cell-permeable protein phosphatase 1 (PP1)/protein phosphatase 2A (PP2A) inhibitor (calyculin A: 25-125 nM) at 37.5 C. After incubation, they were used for immunodetection of phosphorylated proteins, PKA and PP1γ2, assessment for motility and co-immunoprecipitation of PP1γ2 with PKA. Incubation with calyculin A enhanced the phosphorylation states of several proteins (>250 kDa, 170 kDa, 155 kDa, 140 kDa and 42 kDa for serine/threonine phosphorylation and 70 kDa for tyrosine phosphorylation) and PKA catalytic subunits [at the autophosphorylation residue (Thr-197) for its full enzymatic activation] in the flagella. Coincidently, this incubation induced changes of sperm flagellar movement from the progressive type to the hyperactivation-like type. Indirect immunofluorescence and co-immunoprecipitation showed that PKA was co-localized with PP1γ2 in the principal pieces of sperm flagella. These findings suggest that calyculin A-sensitive protein phosphatases (PP1/PP2A) suppress full activation of PKA as well as enhancement of the phosphorylation states of other flagellar proteins in sperm flagella in order to prevent precocious changes of flagellar movement from the progressive type to hyperactivation. Key words: Cyclic adenosine 3',5'-monophosphate (cAMP), Hyperactivation, Protein kinase, Protein phosphatase 1 (PP1), Protein phosphorylation (J. Reprod. Dev. 55: [327][328][329][330][331][332][333][334] 2009) ammalian spermatozoa are differentiated from spermatogonia in the testicular seminiferous tubules and then transferred through the duct of the epididymis. By arrival in the caudal epididymides, they have acquired the potentials to move in a forward direction, bind with the zona pellucida and fertilize oocytes [1], but they are temporally quieted in the epididymis by the influence of the acidic-base status of the luminal fluid [2,3] and interaction with membrane stabilizing factors [4,5]. After ejaculation into the female reproductive tract, the spermatozoa quickly initiate flagellar beating, which is regulated by the protein serine [Ser (S)]/threonine [Thr (T)] phosphorylation in the flagella [6]. Some of the phosphorylated proteins have previously been identified as dynein [6,7] and axokinin [8]. Subsequently, they gradually undergo a series of changes in their intracellular spaces as well as on their cell surfaces (capacitation), including dissociation of decapacitation factors (e.g., cholesterol and acrosomal stabilizing factors), elevation of th...

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“…Brek was reported to bind to and phosphorylate the catalytic subunit of PP1 in vitro (5), suggesting that Brek may play a part in spermatogenesis through the regulation of PP1 activity. One of PP1 isoforms, PP1c␥2, is predominantly expressed in testis (18). Male mice with a targeted disruption of the PP1c␥2 gene showed comparable phenotype with Brek Ϫ/Ϫ mice, severe impairment of spermiogenesis beginning at the round spermatid stage (18).…”

Section: Discussionmentioning

confidence: 92%

Azoospermia in mice with targeted disruption of theBrek/Lmtk2(brain-enriched kinase/lemur tyrosine kinase 2) gene

Kawa¹,

Ito

Toyama

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Brek/Lmtk2 (brain-enriched kinase/lemur tyrosine kinase 2) is a member of the Aatyk family of kinases that comprises Aatyk1, Brek/Lmtk2/Aatyk2, and Aatyk3. Although several potential roles have been proposed for Brek and other Aatyk family members, the physiological functions of these kinases remain unclear. Here, we report that Brek ؊/؊ male mice are infertile, with azoospermia. Detailed histological analysis revealed that Brek ؊/؊ germ cells differentiated normally until the round-spermatid stage, but failed to undergo the normal change in morphology to become elongated spermatids. Testicular somatic cells appeared normal in these mice. Expression of Brek in testis was restricted to the germ cells, suggesting that the maturations of germ cells in Brek ؊/؊ mice are affected in a cell-autonomous manner. On the basis of these findings, we concluded that Brek is essential for a late stage of spermatogenesis. Further clarification of the mechanism by which Brek regulates spermatogenesis may help identify new targets for reproductive contraceptives and treatments against infertility.AATYK ͉ BREK ͉ infertility ͉ LMTK2 ͉ spermatogenesis S permatogenesis, the process by which primordial germ cells generate sperm, is a complex process that includes mitotic division of spermatogonia, meiotic division of spermatocytes to generate haploid cells called spermatids, and differentiation of the spermatids into sperm cells. The last maturation step in which haploid spermatids undergo a complex restructuring program is called spermiogenesis. Spermiogenesis begins with formation of the acrosome from Golgi-derived vesicles, followed by formation of a flagellum, condensation of the nucleus with DNA compaction, and jettison of the cytoplasm. The resulting mature sperm consists of a head with a nucleus and a tail and enters the lumen of the seminiferous tubules. Spermatozoa that differentiate in the testis mature further during the passage through the epididymal duct to acquire functions essential for fertilization.Protein-phosphorylation events play pivotal roles in regulating intracellular signals in response to a wide variety of stimuli. There is accumulating evidence that protein kinases, such as c-Kit, play critical and distinct roles in spermatogenesis (1). Brek (brain-enriched kinase) is a member of the protein kinase subfamily that comprises Aatyk1, Brek/Lmtk2/Aatyk2, and Aatyk3. This kinase subfamily was recently identified through a genome database search for human tyrosine kinases and was tentatively named the Aatyk (apoptosis-associated tyrosine kinase) subfamily (2). Generation of a phyletic tree of known tyrosine and Ser/Thr kinases revealed that Aatyk family kinases represent a previously uncharacterized category of kinases that reside between tyrosine kinases and Ser/Thr kinases. The primary structures of Aatyk kinases show slightly higher homology to tyrosine kinases than to Ser/Thr kinases, but we previously showed that the Aatyk kinases are Ser/Thr kinases and not tyrosine kinases (3). Although Brek is also called A...

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Spermiogenesis Is Impaired in Mice Bearing a Targeted Mutation in the Protein Phosphatase 1cγ Gene

Cited by 138 publications

References 37 publications

The Nuclear RNA-binding Protein Sam68 Translocates to the Cytoplasm and Associates with the Polysomes in Mouse Spermatocytes

The Nuclear RNA-binding Protein Sam68 Translocates to the Cytoplasm and Associates with the Polysomes in Mouse Spermatocytes

Calyculin A-Sensitive Protein Phosphatases are Involved in Maintenance of Progressive Movement in Mouse Spermatozoa In Vitro by Suppression of Autophosphorylation of Protein Kinase A

Azoospermia in mice with targeted disruption of theBrek/Lmtk2(brain-enriched kinase/lemur tyrosine kinase 2) gene

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