Regulating the balance between differentiation and apoptosis: role of CREM in the male germ cells

Peroxisomal testis-specific 1 gene (Pxt1) is the only male germ cell–specific gene that encodes a peroxisomal protein known to date. To elucidate the role of Pxt1 in spermatogenesis, we generated transgenic mice expressing a c-MYC-PXT1 fusion protein under the control of the PGK2 promoter. Overexpression of Pxt1 resulted in induction of male germ cells’ apoptosis mainly in primary spermatocytes, finally leading to male infertility. This prompted us to analyze the proapoptotic character of mouse PXT1, which harbors a BH3-like domain in the N-terminal part. In different cell lines, the overexpression of PXT1 also resulted in a dramatic increase of apoptosis, whereas the deletion of the BH3-like domain significantly reduced cell death events, thereby confirming that the domain is functional and essential for the proapoptotic activity of PXT1. Moreover, we demonstrated that PXT1 interacts with apoptosis regulator BAT3, which, if overexpressed, can protect cells from the PXT1-induced apoptosis. The PXT1-BAT3 association leads to PXT1 relocation from the cytoplasm to the nucleus. In summary, we demonstrated that PXT1 induces apoptosis via the BH3-like domain and that this process is inhibited by BAT3.

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EPC1/TIP60-Mediated Histone Acetylation Facilitates Spermiogenesis in Mice

Molecular and Cellular Biology ◽

10.1128/mcb.00082-17 ◽

2017 ◽

Vol 37 (19) ◽

Cited By ~ 11

Author(s):

Yixin Dong ◽

Kyo-ichi Isono ◽

Kazuyuki Ohbo ◽

Takaho A. Endo ◽

Osamu Ohara ◽

...

Keyword(s):

Histone Acetylation ◽

Germ Cells ◽

Essential Role ◽

Critical Role ◽

Male Germ Cells ◽

Genetic Ablation ◽

Histone Hyperacetylation ◽

Critical Components ◽

Underlying Mechanisms

ABSTRACT Global histone hyperacetylation is suggested to play a critical role for replacement of histones by transition proteins and protamines to compact the genome during spermiogenesis. However, the underlying mechanisms for hyperacetylation-mediated histone replacement remains poorly understood. Here, we report that EPC1 and TIP60, two critical components of the mammalian nucleosome acetyltransferase of H4 (NuA4) complexes, are coexpressed in male germ cells. Strikingly, genetic ablation of either Epc1 or Tip60 disrupts hyperacetylation and impairs histone replacement, in turn causing aberrant spermatid development. Taking these observations together, we reveal an essential role of the NuA4 complexes for histone hyperacetylation and subsequent compaction of the spermatid genome.

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Role of HP1β during spermatogenesis and DNA replication

10.1101/2019.12.22.886424 ◽

2019 ◽

Author(s):

Vijaya Charaka ◽

Anjana Tiwari ◽

Raj K Pandita ◽

Clayton R Hunt ◽

Tej K. Pandita

Keyword(s):

Dna Damage ◽

Dna Replication ◽

Germ Cells ◽

Chromatin Condensation ◽

Genomic Stability ◽

Replication Forks ◽

Chromatin Protein ◽

Male Germ Cells ◽

Chromatin Compaction

AbstractMaintaining genomic stability in a continually dividing cell population requires accurate DNA repair, especially in male germ cells. Repair and replication protein access to DNA, however, is complicated by chromatin compaction. The HP1β chromatin protein, encoded by Cbx1, is associated with chromatin condensation but its role in meiosis is not clear. To investigate the role of Cbx1 in male germ cells, we generated testis specific Cbx1 deficient transgenic mice by crossing Cbx1flox/flox (Cbx1f/f) mice with Stra8 Cre+/− mice. Loss of Cbx1 in testes adversely affected sperm maturation and Cbx1 deletion increased seminiferous tubule degeneration and basal level DNA damage., We observed that Cbx1−/− MEF cells displayed reduced resolution of stalled DNA replication forks as well as decreased fork restart, indicating defective DNA synthesis. Taken together, these results suggest that loss of Cbx1 in growing cells leads to DNA replication defects and associated DNA damage that impact cell survival.

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Bone morphogenetic protein 8A plays a role in the maintenance of spermatogenesis and the integrity of the epididymis

Development ◽

10.1242/dev.125.6.1103 ◽

1998 ◽

Vol 125 (6) ◽

pp. 1103-1112 ◽

Cited By ~ 1

Author(s):

G.Q. Zhao ◽

L. Liaw ◽

B.L. Hogan

Keyword(s):

Germ Cell ◽

Germ Cells ◽

Targeted Mutagenesis ◽

Chromosome 4 ◽

Female Reproduction ◽

Cell Degeneration ◽

Male Germ Cells ◽

Morphogenetic Protein ◽

Germ Cell Degeneration

The murine Bmp8a and Bmp8b genes are tightly linked on mouse chromosome 4 and have similar expression during reproduction. Previous studies have shown that targeted mutagenesis of Bmp8b causes male infertility due to germ cell degeneration. To investigate the function of Bmp8a, we have inactivated the gene by homologous recombination. Heterozygous and homozygous Bmp8a mutants reveal normal embryonic and postnatal development. Despite high levels of Bmp8a expression in the deciduum, homozygous mutant females have normal fertility, suggesting that the gene is not essential for female reproduction. Bmp8a and Bmp8b are expressed in similar patterns in male germ cells. Unlike homozygous Bmp8btm1 mutants, homozygous Bmp8atm1 males do not show obvious germ cell defects during the initiation of spermatogenesis. However, germ cell degeneration is observed in 47% of adult homozygous Bmp8atm1 males, establishing a role of Bmp8a in the maintenance of spermatogenesis. A small proportion of the mating homozygous Bmp8atm1 males also show degeneration of the epididymal epithelium, indicating a novel role for BMPs in the control of epididymal function.

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Nodal Signaling Regulates the Entry into Meiosis in Fetal Germ Cells

Endocrinology ◽

10.1210/en.2011-2056 ◽

2012 ◽

Vol 153 (5) ◽

pp. 2466-2473 ◽

Cited By ~ 45

Author(s):

Benoit Souquet ◽

Sophie Tourpin ◽

Sébastien Messiaen ◽

Delphine Moison ◽

René Habert ◽

...

Keyword(s):

Germ Cell ◽

Germ Cells ◽

Target Genes ◽

Normal Male ◽

Nodal Signaling ◽

Male Germ Cells ◽

Embryonic Germ Cells ◽

Meiotic Inhibitors ◽

First Time

The mechanisms regulating the entry into meiosis in mammalian germ cells remain incompletely understood. We investigated the involvement of the TGF-β family members in fetal germ cell meiosis initiation. Nodal, a member of the TGF-β family, and its target genes are precociously expressed in embryonic gonads and show sexual dimorphism in favor of the developing testis. Nodal receptor genes, Acvr2a and Acvr2b, Alk4, and Tdgf1/Cripto, were identified in male germ cells. Nodal itself, Tdgf1, and Lefty1 and Lefty2 are targets of Nodal signaling and were all found specifically expressed in male germ cells. To elucidate the role of this signaling pathway, activin-like kinases that mediate TGF-β/Nodal/activin signaling were inhibited in 11.5 d postconception testis in organotypic culture. Activin-like kinases inhibition disrupted normal male germ cell development and induced germ cell entry into meiosis such as that observed in female germ cells at the equivalent stage. Interestingly Stra8, the gatekeeper of the mitotic/meiotic switch, was induced independently of any change of either Cyp26b1 or Fgf9 expression, the two genes currently identified as testicular meiotic inhibitors. On the other hand, recombinant Nodal significantly dampened Stra8 expression and germ cell meiosis in cultured 11.5 d postconception ovaries. Our results allowed us to propose for the first time an autocrine role of Nodal during the development of germ cells and indicate that members of the TGB-β family may reinforce the male fate and prevent meiosis in embryonic germ cells.

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Maintenance DNA methylation in pre-meiotic germ cells regulates meiotic prophase by facilitating homologous chromosome pairing

Development ◽

10.1242/dev.194605 ◽

2021 ◽

Vol 148 (10) ◽

Author(s):

Yuki Takada ◽

Ruken Yaman-Deveci ◽

Takayuki Shirakawa ◽

Jafar Sharif ◽

Shin-ichi Tomizawa ◽

...

Keyword(s):

Dna Methylation ◽

Germ Cells ◽

Meiotic Prophase ◽

De Novo ◽

Pericentric Heterochromatin ◽

Male Germ Cells ◽

Homologous Chromosomes ◽

Homologous Chromosome Pairing ◽

Synaptic Failure

ABSTRACT Heterochromatin-related epigenetic mechanisms, such as DNA methylation, facilitate pairing of homologous chromosomes during the meiotic prophase of mammalian spermatogenesis. In pro-spermatogonia, de novo DNA methylation plays a key role in completing meiotic prophase and initiating meiotic division. However, the role of maintenance DNA methylation in the regulation of meiosis, especially in the adult, is not well understood. Here, we reveal that NP95 (also known as UHRF1) and DNMT1 – two essential proteins for maintenance DNA methylation – are co-expressed in spermatogonia and are necessary for meiosis in male germ cells. We find that Np95- or Dnmt1-deficient spermatocytes exhibit spermatogenic defects characterized by synaptic failure during meiotic prophase. In addition, assembly of pericentric heterochromatin clusters in early meiotic prophase, a phenomenon that is required for subsequent pairing of homologous chromosomes, is disrupted in both mutants. Based on these observations, we propose that DNA methylation, established in pre-meiotic spermatogonia, regulates synapsis of homologous chromosomes and, in turn, quality control of male germ cells. Maintenance DNA methylation, therefore, plays a role in ensuring faithful transmission of both genetic and epigenetic information to offspring.

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MORC3, a novel MIWI2 association partner, as an epigenetic regulator of piRNA dependent transposon silencing in male germ cells

Scientific Reports ◽

10.1038/s41598-021-98940-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Kanako Kojima-Kita ◽

Satomi Kuramochi-Miyagawa ◽

Manabu Nakayama ◽

Haruhiko Miyata ◽

Steven E. Jacobsen ◽

...

Keyword(s):

Dna Methylation ◽

Germ Cells ◽

De Novo ◽

Effector Proteins ◽

P Element ◽

Male Germ Cells ◽

Transposon Silencing ◽

Association Partner ◽

Pirna Pathway

AbstractThe PIWI (P-element-induced wimpy testis)-interacting-RNA (piRNA) pathway plays a crucial role in the repression of TE (transposable element) expression via de novo DNA methylation in mouse embryonic male germ cells. Various proteins, including MIWI2 are involved in the process. TE silencing is ensured by piRNA-guided MIWI2 that recruits some effector proteins of the DNA methylation machinery to TE regions. However, the molecular mechanism underlying the methylation is complex and has not been fully elucidated. Here, we identified MORC3 as a novel associating partner of MIWI2 and also a nuclear effector of retrotransposon silencing via piRNA-dependent de novo DNA methylation in embryonic testis. Moreover, we show that MORC3 is important for transcription of piRNA precursors and subsequently affects piRNA production. Thus, we provide the first mechanistic insights into the role of this effector protein in the first stage of piRNA biogenesis in embryonic TE silencing mechanism.

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On the role of germ cells in planarian regeneration

Development ◽

10.1242/dev.55.1.65 ◽

1980 ◽

Vol 55 (1) ◽

pp. 65-76

Author(s):

V. Gremigni ◽

C. Miceli ◽

E. Picano

Keyword(s):

Germ Cells ◽

Dna Content ◽

Somatic Cells ◽

Diploid Male ◽

Dna Amount ◽

Male Germ Cells ◽

Blastema Formation ◽

Planarian Regeneration ◽

Cytophotometric Analysis

Previous findings by our group have shown how primordial male germ cells take part in regenerative blastema formation in planarians by migrating to the wound. The role of these cells in rebuilding transected tissues has been investigated in a population of Dugesia lugubris s.l. which is particularly suited for our purpose. In fact, these planarians provide a clear karyological marker to distinguish diploid male germ cells (2n = 8) from tryploid embryonic or somatic cells (3n = 12). In this study we employed the cytophotometric analysis of the nuclear Feulgen-DNA content in order to distinguish non-replicating male germ cells from reserve and somatic cells. The Feulgen-DNA content in cells from the gonad-free caudal area was measured after complete regeneration. Most non-replicating cells (94–95%) were found to have a DNA amount typical of cells previously estimated as triploid. Some (5–6%) nuclei containing a DNA amount typical of cells previously estimated as diploid male gonia were also found. These findings seem to support the view that primordial male germ cells also participate in rebuilding somatic tissues according to the field influence they encounter during regeneration. The possibility that metaplasia (or cell transdifferentiation) may occur in planarians is finally discussed.

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