Efficient enrichment of synchronized mouse spermatocytes suitable for genome-wide analysis.

Chromatin-based mechanisms regulating developmental transitions during meiosis are fundamental but understudied aspects of male gametogenesis. Indeed, chromatin undergoes extensive remodeling dur-ing meiosis, leading to specific patterns of gene expression and chromosome organization, which ulti-mately controls fundamental meiotic processes such as recombination and homologous chromosome associations. Recent game-changing advances have been made by analysis of chromatin binding sites of meiotic specific proteins genome-wide in mouse spermatocytes. However, further progress is still highly dependent on the reliable isolation of sufficient quantities of spermatocytes at specific stages of prophase I. Here, we describe a combination of methodologies adapted for rapid and reliable isolation of synchronized fixed mouse spermatocytes. We show that chromatin isolated from these cells can be used to study chromatin binding sites by ChIP-seq. High quality data we obtained from INO80 ChIP-seq in zygotene cells was used for functional analysis of chromatin binding sites.

Plasmodium falciparum Calcium-Dependent Protein Kinase 4 is Critical for Male Gametogenesis and Transmission to the Mosquito Vector

Transmission of the malaria parasite to the mosquito vector is critical for the completion of the sexual stage of the parasite life cycle and is dependent on the release of male gametes from the gametocyte body inside the mosquito midgut. In the present study, we demonstrate that PfCDPK4 is critical for male gametogenesis and is involved in phosphorylation of proteins essential for male gamete emergence.

Distinct roles of haspin in stem cell division and male gametogenesis

The kinase haspin phosphorylates histone H3 at threonine-3 (H3T3ph) during mitosis. H3T3ph provides a docking site for the Chromosomal Passenger Complex at the centromere, enabling correction of erratic microtubule-chromosome contacts. Although this mechanism is operational in all dividing cells, haspin-null mice do not exhibit developmental anomalies, apart from aberrant testis architecture. Investigating this problem, we show here that mouse embryonic stem cells that lack or overexpress haspin, albeit prone to chromosome misalignment during metaphase, can still divide, expand and differentiate. RNA sequencing reveals that haspin dosage affects severely the expression levels of several genes that are involved in male gametogenesis. Consistent with a role in testis-specific expression, H3T3ph is detected not only in mitotic spermatogonia and meiotic spermatocytes, but also in non-dividing cells, such as haploid spermatids. Similarly to somatic cells, the mark is erased in the end of meiotic divisions, but re-installed during spermatid maturation, subsequent to methylation of histone H3 at lysine-4 (H3K4me3) and arginine-8 (H3R8me2). These serial modifications are particularly enriched in chromatin domains containing histone H3 trimethylated at lysine-27 (H3K27me3), but devoid of histone H3 trimethylated at lysine-9 (H3K9me3). The unique spatio-temporal pattern of histone H3 modifications implicates haspin in the epigenetic control of spermiogenesis.

Plasmodium falciparum Calcium Dependent Protein Kinase 4 is critical for male gametogenesis and transmission to the mosquito vector

Gametocytes of the malaria parasite Plasmodium are taken up by the mosquito vector with an infectious blood meal, representing a critical stage for parasite transmission. Calcium dependent protein kinases play key roles in calcium mediated signaling across the complex life cycle of the parasite. We sought to understand their role in human parasite transmission from the host to the mosquito vector and thus investigated the role of the human infective parasite Plasmodium falciparum CDPK4 in the parasite life cycle. P. falciparum cdpk4 parasites created by targeted gene deletion showed no effect in blood stage development or gametocyte development. However, cdpk4 parasites showed a severe defect in male gametogenesis and the emergence of flagellated male gametes. To understand the molecular underpinnings of this defect, we performed mass spectrometry based phosphoproteomic analyses of wild type and Plasmodium falciparum cdpk4 late gametocyte stages, to identify key CDPK4 mediated phosphorylation events that may be important for the regulation of male gametogenesis. We further employed in vitro assays to identify these putative substrates of Plasmodium falciparum CDPK4. This indicated that CDPK4 regulates male gametogenesis by directly or indirectly controlling key essential events such as DNA replication, mRNA translation and cell motility. Taken together, our work demonstrates that PfCDPK4 is a central kinase that regulates exflagellation, and thereby is critical for parasite transmission to the mosquito vector.

Sperm acrosome overgrowth and infertility in mice lacking chromosome 18 pachytene piRNA

piRNAs are small non-coding RNAs required to maintain genome integrity and preserve RNA homeostasis during male gametogenesis. In murine adult testes, the highest levels of piRNAs are present in the pachytene stage of meiosis, but their mode of action and function remain incompletely understood. We previously reported that BTBD18 binds to 50 pachytene piRNA-producing loci. Here we show that spermatozoa in gene-edited mice lacking a BTBD18 targeted pachytene piRNA cluster on Chr18 have severe sperm head dysmorphology, poor motility, impaired acrosome exocytosis, zona pellucida penetration and are sterile. The mutant phenotype arises from aberrant formation of proacrosomal vesicles, distortion of the trans-Golgi network, and up-regulation of GOLGA2 transcripts and protein associated with acrosome dysgenesis. Collectively, our findings reveal central role of pachytene piRNAs in controlling spermiogenesis and male fertility.

Sperm acrosome overgrowth and infertility in mice lacking chromosome 18 pachytene piRNA

AbstractpiRNAs are germline-specific, small non-coding RNAs required to maintain genome integrity and preserve RNA homeostasis during male gametogenesis. In murine adult testes, the highest levels of piRNAs are present in the pachytene stage of meiosis, but their mode of action and function remains incompletely understood. We previously reported that BTBD18 binds to 50 pachytene piRNA-producing loci. Here we show that spermatozoa in gene-edited mice lacking a BTBD18 targeted pachytene piRNA cluster on Chr18 have severe sperm head dysmorphology, poor motility, impaired acrosome exocytosis and are sterile. The absence of Chr18 piRNA results in an imbalance of heat shock proteins associated with renaturing proteins and the ubiquitin-proteasome system involved with protein degradation. The mutant phenotype arises from aberrant formation of proacrosomal vesicles, distortion of the trans-Golgi network, and up-regulation of GOLGA2 associated with acrosome dysgenesis. Collectively, our findings reveal central role of pachytene piRNAs in controlling spermiogenesis and male fertility.