Project description:Idiopathic fertility disorders are associated with mutations in various genes. Here, we report that coiled-coil glutamate-rich protein 1 (CCER1), a germline-specific and intrinsically disordered protein (IDP), mediates post-meiotic sperm differentiation, while CCER1 deficiency results in defective sperm chromatin compaction and infertility in mice. CCER1 increases transition protein (Tnp1/2) and protamine (Prm1/2) transcription and serves as a multifaceted mediator for multiple epigenetic modification events of histones during the histone to protamine transition (HTP). Immiscible with heterochromatin in the nucleus, CCER1 self-assembles into polymer droplet and acts as a liquid-liquid phase separated condensate in the nucleus. Notably, we identified the loss-of function variants of human CCER1 (hCCER1) in five patients with non-obstuctive azoospermia (NOA) while absent in 2,713 fertile controls. The mutants led to premature termination or frameshift of CCER1 translation and disrupted condensates in vitro. In conclusion, we propose that nuclear CCER1 is a novel phase-separated condensate that links histone epigenetic modifications, sperm HTP transitions, chromatin condensation, and male fertility.
Project description:Idiopathic fertility disorders are associated with mutations in various genes. Here, we report that coiled-coil glutamate-rich protein 1 (CCER1), a germline-specific and intrinsically disordered protein (IDP), mediates postmeiotic spermatid differentiation. In contrast, CCER1 deficiency results in defective sperm chromatin compaction and infertility in mice. CCER1 increases transition protein (Tnp1/2) and protamine (Prm1/2) transcription and mediates multiple histone epigenetic modifications during the histone-to-protamine (HTP) transition. Immiscible with heterochromatin in the nucleus, CCER1 self-assembles into a polymer droplet and forms a liquid-liquid phase-separated condensate in the nucleus. Notably, we identified loss-of-function (LoF) variants of human CCER1 (hCCER1) in five patients with nonobstructive azoospermia (NOA) that were absent in 2713 fertile controls. The mutants led to premature termination or frameshift in CCER1 translation, and disrupted condensates in vitro. In conclusion, we propose that nuclear CCER1 is a phase-separated condensate that links histone epigenetic modifications, HTP transitions, chromatin condensation, and male fertility.
Project description:Protamines replace histones as the main nuclear protein in sperm cells having a crucial role in compacting the paternal genome. Human spermatozoa contain the protamine 1 (P1) and the family of protamine 2 (P2) proteins. Alterations in protamine PTMs or on the P1/P2 ratio could be associated with male infertility. Top-down proteomics enables large-scale analysis of intact proteforms derived from alternative splicing, missense or nonsense genetic variants or PTMs. In contrast to current gold standard techniques, top-down allows a more in-depth analysis of protamine PTMs and proteoforms, opening up new perspectives to unravel their impact on male fertility. We analyzed two normozoospermic semen samples by top-down and discussed in detail the difficulties we found in the data analysis and the suggested solutions, as this step is one of the current bottlenecks in top-down proteomics with currently available bioinformatic tools. Our strategy for the data analysis combines two different software, ProSight PD (PS) and TopPIC suite (TP), with a clustering algorithm to decipher protamine proteoforms. We identified up to 32 protamine proteoforms at different levels of characterization. This in-depth analysis of the protamine proteoform landscape of an individual boosts personalized diagnosis of male infertility.
Project description:Conventional dogma presumes that protamine-mediated DNA compaction in sperm is achieved by electrostatic interactions between DNA and the arginine-rich core of protamines. However, phylogenetic analysis reveals several non-arginine residues conserved within, but not across species. The significance of these residues or post-translational modifications are poorly understood. Here, we investigated the functional role of K49, a rodent-specific lysine residue in mouse protamine 1 (P1) that is acetylated early in spermiogenesis and retained in sperm. In vivo, alanine substitution (P1 K49A) results in loss of programmatic histone retention, decreased sperm motility, decreased male fertility, and in zygotes, premature P1 removal from paternal chromatin, altered DNA replication, and embryonic arrest. In vitro, P1 K49A decreases protamine-DNA binding and alters DNA compaction/decompaction kinetics. Hence, a single amino acid substitution outside the P1 arginine core is sufficient to profoundly alter protein function and developmental outcomes, suggesting that protamine non-arginine residues are essential for reproductive fitness.
Project description:Unique chromatin remodeling factors orchestrate dramatic changes in nuclear morphology during differentiation of the mature sperm head. A critical step in this process is histone-to-protamine exchange, which must be executed correctly to avoid sperm DNA damage, embryonic lethality, and male sterility. Here, we define an essential role for the histone methyltransferase DOT1L in the histone-to-protamine transition. We show that DOT1L is abundantly expressed in meiotic and postmeiotic germ cells and that methylation of histone H3 lysine 79 (H3K79), the modification catalyzed by DOT1L, is enriched in developing spermatids in the initial stages of histone replacement. Elongating spermatids lacking DOT1L fail to fully replace histones and exhibit aberrant protamine recruitment, resulting in deformed sperm heads and male sterility. Loss of DOT1L results in transcriptional dysregulation coinciding with the onset of histone replacement and affecting genes required for histone-to-protamine exchange. DOT1L also deposits H3K79me2 and promotes accumulation of elongating RNA Polymerase II at the testis-specific bromodomain gene Brdt. Together, our results indicate that DOT1L is an important mediator of transcription during spermatid differentiation and an indispensable regulator of male fertility.
Project description:Conventional dogma presumes that protamine-mediated DNA compaction in sperm is achieved by electrostatic interactions between DNA and the arginine-rich core of protamines. However, phylogenetic analysis reveals several non-arginine residues conserved within, but not across species. The significance of these residues or post-translational modifications are poorly understood. Here, we investigated the functional role of K49, a rodent-specific lysine residue in mouse protamine 1 (P1) that is acetylated early in spermiogenesis and retained in sperm. In vivo, alanine substitution (P1 K49A) results in loss of programmatic histone retention, decreased sperm motility, decreased male fertility, and in zygotes, premature P1 removal from paternal chromatin, altered DNA replication, and embryonic arrest. In vitro, P1 K49A decreases protamine-DNA binding and alters DNA compaction/decompaction kinetics. Hence, a single amino acid substitution outside the P1 arginine core is sufficient to profoundly alter protein function and developmental outcomes, suggesting that protamine non-arginine residues are essential for reproductive fitness.
Project description:Conventional dogma presumes that protamine-mediated DNA compaction in sperm is achieved by electrostatic interactions between DNA and the arginine-rich core of protamines. However, phylogenetic analysis reveals several non-arginine residues conserved within, but not across species. The significance of these residues or post-translational modifications are poorly understood. Here, we investigated the functional role of K49, a rodent-specific lysine residue in mouse protamine 1 (P1) that is acetylated early in spermiogenesis and retained in sperm. In vivo, alanine substitution (P1 K49A) results in loss of programmatic histone retention, decreased sperm motility, decreased male fertility, and in zygotes, premature P1 removal from paternal chromatin, altered DNA replication, and embryonic arrest. In vitro, P1 K49A decreases protamine-DNA binding and alters DNA compaction/decompaction kinetics. Hence, a single amino acid substitution outside the P1 arginine core is sufficient to profoundly alter protein function and developmental outcomes, suggesting that protamine non-arginine residues are essential for reproductive fitness.
Project description:Protamine 1 (P1) and protamine 2 family (P2) are the most abundant nuclear basic spermspecific proteins, packing 85-95% of the paternal DNA. P1 is synthesized as a mature form, whereas P2 components (HP2, HP3 and HP4) arise from the proteolysis of the precursor (pre-P2). Due to the particular protamine physical-chemical properties, their identification by standardized bottom-up mass spectrometry (MS) strategies are not straightforward. Therefore, the aim of this study was to identify the sperm protamine proteoforms profile including P1 and P2 members and their post-translational modifications in normozoospermic individuals using two complementary strategies, a top-down MS approach and a proteinase K-digestion based bottom-up MS approach. By top-down MS approach, both described and new truncated P1 and pre-P2 proteoforms were identified. Likewise, intact P1, pre-P2, and P2 mature forms and their phosphorylation pattern were detected, as well as a +61 Da modification in different proteoforms. Additionally, the bottom-up MS approach revealed phosphorylated residues for pre-P2 and the new P2 isoform 2, which is not annotated at UniProtKB database. Implementing these strategies in comparative studies of different infertile phenotypes would permit to determine alterations in the protamine proteoforms pattern and elucidate the role of phosphorylation/dephosphorylation dynamics in male fertility.
Project description:Sperm carries information to the presumptive embryo upon fertilization in terms of epigenetic codes and transcripts along with the haploid genome. The epigenetic code includes DNA methylation and Histone modifications. During spermatogenesis the chromatin of sperm undergoes wide level of modifications and histone proteins are replaced by Protamine proteins. But some modified Histone forms still remain and they carry epigenetic codes essential for fertility and embryo development. Through this work we are trying to see the difference between H3K4me2 and H3K27me3 kind of histone modifications in spermatozoa of high and low fertility buffalo bulls.