Biology subjects

Wyrwoll, M. J.

Publications and source records attributed to Wyrwoll, M. J..

4 recordsLinked to original sources

bioRxiv2022

Stage-specific gene and transcript dynamics in human male germ cells

Cell differentiation processes are highly dependent on cell stage-specific gene expression, including timely production of alternatively spliced transcripts. One of the most transcriptionally rich tissues is the testis, where the process of spermatogenesis, or generation of male gametes, takes place. To date, germ cell-specific transcriptome dynamics remain understudied due to limited transcript information emerging from short-read sequencing technologies. To fully characterize the transcriptional profiles of human male germ cells and to understand how the human spermatogenic transcriptome is regulated, we compared whole transcriptomes of men with different types of germ cells missing from their testis. Specifically, we compared the transcriptomes of testis lacking germ cells (Sertoli cell-only phenotype; SCO; n=3), with an arrest at the stage of spermatogonia (SPG; n=4), spermatocytes (SPC; n=3), and round spermatids (SPD; n=3), with the transcriptomes of testis with normal and complete spermatogenesis (Normal; n=3). We found between 839 and 4,138 differentially expressed genes (DEGs, log2 fold change [≥] 1) per group comparison, with the most prevalent changes observed between SPG and SPC arrest samples, corresponding to the entry into meiosis. We detected highly germ cell-type specific marker genes among the topmost DEGs of each group comparison. Moreover, applying state-of-the-art bioinformatic analysis we were able to evaluate differential transcript usage (DTU) during human spermatogenesis and observed between 1,062 and 2,153 genes with alternatively spliced transcripts per group comparison. Intriguingly, DEGs and DTU genes showed minimal overlap (< 8%), suggesting that stage-specific splicing is an additional layer of gene regulation in the germline. By generating the most complete human testicular germ cell transcriptome to date, we unravel extensive dynamics in gene expression and alternative splicing during human spermatogenesis.

molecular biology↗

bioRxiv2022

The conserved transcriptional program of metazoan male germ cells uncovers ancient origins of human infertility

Male germ cells share a common origin across animal species, therefore they likely retain a conserved genetic program that defines their cellular identity. However, the unique evolutionary dynamics of male germ cells coupled with their widespread leaky transcription pose significant obstacles to the identification of the core spermatogenic program. Through network analysis of the spermatocyte transcriptome of vertebrate and invertebrate species, we describe the conserved evolutionary origin of metazoan male germ cells at the molecular level. We estimate the average functional requirement of a metazoan male germ cell to correspond to the expression of approximately 10,000 protein-coding genes, a third of which defines a genetic scaffold of deeply conserved genes that has been retained throughout evolution. Such scaffold contains a set of 79 functional associations between 104 gene expression regulators that represent a core component of the conserved genetic program of metazoan spermatogenesis. By genetically interfering with the acquisition and maintenance of male germ cell identity, we uncover 161 previously unknown spermatogenesis genes and three new potential genetic causes of human infertility. These findings emphasize the importance of evolutionary history on human reproductive disease and establish a cross-species analytical pipeline that can be repurposed to other cell types and pathologies.

systems biology↗

bioRxiv2021

EGR4-dependent decrease of UTF1 is associated with failure to reserve spermatogonial stem cells in infertile men

Despite the high incidence of male infertility, about 70% of infertile men do not receive a causative diagnosis. To gain insights into the regulatory mechanisms governing human germ cell function in normal and impaired spermatogenesis (cryptozoospermic patients, crypto), we combined single cell RNA sequencing (>30.000 cells), proteome, and histomorphometric analyses of testicular tissues. We found major alterations in the crypto spermatogonial compartment with increased numbers of the most undifferentiated spermatogonia (PIWIL4+ State 0 cells). We also observed a transcriptional switch within the spermatogonial compartment driven by the increased and prolonged expression of the transcription factor EGR4. Intriguingly, EGR4-regulated genes included the chromatin-associated transcriptional repressor UTF1, which was downregulated. Histomorphometrical analyses showed that these transcriptional changes were mirrored at the protein level and accompanied by a change in the chromatin structure of spermatogonia. This resulted in a reduction of Adark spermatogonia - characterized by tightly compacted chromatin and serving as reserve stem cells. These findings suggest that crypto patients are at a disadvantage especially in cases of gonadotoxic damage as they have less cells safeguarding the genetic integrity of the germline. We hypothesize that the more relaxed chromatin status of spermatogonia is dependent on decreased UTF1 expression caused by EGR4 activation. These identified regulators of the spermatogonial compartment will be highly interesting targets to uncover genetic causes of male infertility. One Sentence SummaryReserve spermatogonial stem cell depletion in infertile men is regulated by an EGR4-dependent UTF1 decrease, which changes chromatin morphology.

molecular biology↗

bioRxiv2019

Biallelic mutations in M1AP are a frequent cause of meiotic arrest leading to male infertility

Male infertility affects [~]7% of men in Western societies, but its causes remain poorly understood. The most clinically severe form of male infertility is non-obstructive azoospermia (NOA), which is, in part, caused by an arrest at meiosis, but so far only few genes have been reported to cause germ cell arrest in males. To address this gap, whole exome sequencing was performed in 60 German men with complete meiotic arrest, and we identified in three unrelated men the same homozygous frameshift variant c.676dup (p.Trp226LeufsTer4) in M1AP, encoding meiosis 1 arresting protein. Then, with collaborators from the International Male Infertility Genomics Consortium (IMIGC), we screened a Dutch cohort comprising 99 infertile men and detected the same homozygous variant c.676dup in a man with hypospermatogenesis predominantly displaying meiotic arrest. We also identified two Portuguese men with NOA carrying likely biallelic loss-of-function (LoF) and missense variants in M1AP among men screened by the Genetics of Male Infertility Initiative (GEMINI). Moreover, we discovered a homozygous missense variant p.(Pro389Leu) in M1AP in a consanguineous Turkish family comprising five infertile men. M1AP is predominantly expressed in human and mouse spermatogonia up to secondary spermatocytes and previous studies have shown that knockout male mice are infertile due to meiotic arrest. Collectively, these findings demonstrate that both LoF and missense M1AP variants that impair its protein cause autosomal-recessive meiotic arrest, non-obstructive azoospermia and male infertility. In view of the evidence from several independent groups and populations, M1AP should be included in the growing list of validated NOA genes.

genetics↗