Germ cell progression through zebrafish spermatogenesis declines with age

Zbtb48 is a regulator of Mtfp1 expression in zebrafish

ZBTB48 (also known as TZAP) is a transcription factor that has previously been reported to bind to telomeres and act as a negative regulator of telomere length in human cell lines. To explore whether transcription factor activity and telomere length regulation are conserved at the organismal level in vertebrates, we generate a zbtb48-/- zebrafish line via CRISPR‒Cas genome editing. The zbtb48-/- mutants display no obvious physical or behavioral abnormalities in the first two generations. We find no statistically significant changes in telomere length in first-generation adults. However, for the gene regulatory aspect of Zbtb48, similar to that in human cancer cell lines, we observe downregulation of mtfp1 at both the mRNA and protein levels in the zbtb48-/- mutants. This suggests that mtfp1 is an evolutionarily conserved regulatory target of Zbtb48. Further investigation of the spatiotemporal expression of zbtb48 in previously published zebrafish data reveals low transcript expression in diverse tissues, except in germline stem cells and gametocytes of the gonads. Notably, Mtfp1 protein downregulation is detected in the ovaries of 40 dpf zbtb48-/- mutants and in the testes of both 40 dpf and 10.5-month-old zbtb48-/- mutants.

Comprehensive analysis of long non-coding RNA and mRNA expression patterns during seminiferous tubules maturation in Guanzhong dairy goats

BACKGROUND

Long non-coding RNAs (lncRNAs) play crucial roles in testicular development and spermatogenesis. The seminiferous tubule, the exclusive site of spermatogenesis, houses all types of male germ cells, regulated by both lncRNAs and mRNAs. However, the expression patterns and functions of these molecules across different developmental stages of dairy goat seminiferous tubules remain poorly understood.

RESULTS

In this study, we sequenced and identified lncRNAs and mRNAs expressed in the seminiferous tubules of Guanzhong dairy goats at two developmental stages: 45-day-old premature (G45) and 240-day-old mature (G240). Significant differences in testis index and seminiferous tubules morphology were observed between G45 and G240 (P < 0.05). Transcriptome analyses revealed 11,612 lncRNAs and 18,217 mRNAs, with 7,554 lncRNAs and 11,986 mRNAs showing significant differential expression between the two stages. Among these, 229 differentially expressed mRNAs related to spermatogenesis were identified. Key genes, such as Kit, Dmrt1, and Sox9, were down-regulated, whereas Ddx4, Sycp1, and Sycp3 were up-regulated after sexual maturity. Notably, signalling pathways including PI3K/Akt, MAPK, and Rap1 were implicated in the regulation of spermatogenesis. We constructed lncRNA-mRNA interaction networks, identifying specific lncRNAs and their target genes potentially critical for spermatogenesis. Additionally, single-cell transcriptome data validated the expression of key genes, revealing that Piwil4 and Dnmt3l were specifically expressed in spermatogonial clusters, whereas Piwil1, Piwil2, and Gtsf1 were predominantly expressed in spermatocyte clusters.

CONCLUSIONS

These findings highlight the essential roles of specific genes in the maturation of seminiferous tubules in dairy goats. This study provides comprehensive transcriptomic profiles and lncRNA-mRNA interaction networks between the G45 and G240 stages, offering valuable insights into spermatogenesis and seminiferous tubules development in Guanzhong dairy goats.

Dynamic interplay of cNHEJ and MMEJ pathways of DNA double-strand break repair during embryonic development in zebrafish

Double strand breaks (DSBs) are the most deleterious DNA lesions as they frequently result in mutations when repaired by canonical non homologous end-joining (cNHEJ) and microhomology-mediated end-joining (MMEJ). Here, we investigated the relative importance of cNHEJ and MMEJ pathways during zebrafish embryonic development. We have analyzed the expression of cNHEJ and MMEJ related genes and found that it was dynamic during development and often become increased in specific tissues. We showed that inactivation of nuclear DNA ligase 3 (nLig3) or DNA polymerase theta (Polθ), two key MMEJ factors, did not affect zebrafish development but sensitized embryos to ionizing radiations and that deficiency of Polθ, but not nLig3, profoundly alters the mutation spectrum induced during repair of Cas9-mediated DSBs. By contrast, inactivation of DNA ligase 4, required for cNHEJ, did not seem to sensitize embryos to ionizing radiations nor to affect repair of Cas9-mediated DSBs but resulted in important larval growth defects. Our study underscores the dynamic and context-dependent roles of cNHEJ and MMEJ pathways during zebrafish development, highlighting their differential requirements across developmental stages and in response to genotoxic stress.