Biology subjects

Cremers, J.-F.

Publications and source records attributed to Cremers, J.-F..

4 recordsLinked to original sources

bioRxiv2026

A single-nucleus multiomic and spatial atlas of gene regulation in human spermatogenesis

Gametogenesis, the production of oocytes and sperm, ensures the faithful transmission of genetic material to the next generation. In males, spermatogenesis occurs within the testis, where germ cells progress through a highly ordered developmental programme in close association with supporting somatic cells. Defects in this process cause infertility, yet the gene regulatory mechanisms coordinating normal and dysfunctional human spermatogenesis remain incompletely defined. Here we generate a single-nucleus multiomic and spatial atlas of human spermatogenesis by profiling chromatin accessibility and gene expression in the same nuclei and integrating these data with spatial transcriptomics of intact testicular tissue. We infer high-confidence gene regulatory networks that resolve stage-specific activity of known and novel candidate regulators across germline and somatic compartments, and map spatially restricted signalling interactions within the seminiferous tubule niche. Integration with infertility-associated genetic variation links non-coding risk loci to candidate enhancers and target genes in cell-type-specific regulatory contexts. Finally, profiling clinical cryptozoospermia samples as in vivo perturbations supports the ability of this network to capture downstream transcriptional consequences of disease-associated regulatory disruption. Together, these data provide a spatially resolved regulatory framework for human spermatogenesis and a foundation for interpreting the molecular basis of male infertility.

genomics↗

bioRxiv2023

Genome-wide DNA methylation changes in human spermatogenesis

Sperm production and function require the correct establishment of DNA methylation patterns in the germline. Here, we examined the genome-wide DNA methylation changes during human spermatogenesis and its alterations in disturbed spermatogenesis. We found that spermatogenesis is associated with remodeling of the methylome, comprising a global-decline in DNA methylation in primary spermatocytes followed by selective remethylation, resulting in a spermatid-specific methylome. Hypomethylated regions in spermatids were enriched in specific transcription factor binding sites for DMRT and SOX family members and spermatid-specific genes. Intriguingly, while SINEs displayed differential methylation throughout spermatogenesis, LINEs appeared to be protected from changes in DNA methylation. In disturbed spermatogenesis, germ cells exhibited considerable DNA methylation changes, which were significantly enriched at transposable elements and genes involved in spermatogenesis. We detected hypomethylation in SVA and L1HS in disturbed spermatogenesis, suggesting an association between the abnormal programming of these regions and failure of germ cells progressing beyond meiosis.

genetics↗

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↗

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↗