Single-cell RNA-sequencing reveals the transcriptional landscape of ND-42 mediated spermatid elongation via mitochondrial derivative maintenance in Drosophila testes

During spermatogenesis, mitochondria extend along the whole length of spermatid tail and offer a structural platform for microtubule reorganization and synchronized spermatid individualization, that eventually helps to generate mature sperm in Drosophila. However, the regulatory mechanism of spermatid mitochondria during elongation remains largely unknown. Herein, we demonstrated that NADH dehydrogenase (ubiquinone) 42 kDa subunit (ND-42) was essential for male fertility and spermatid elongation in Drosophila. Moreover, ND-42 depletion led to mitochondrial disorders in Drosophila testes. Based on single-cell RNA-sequencing (scRNA-seq), we identified 15 distinct cell clusters, including several unanticipated transitional subpopulations or differ-entiative stages for testicular germ cell complexity in Drosophila testes. Enrichments of the transcriptional reg-ulatory network in the late-stage cell populations revealed key roles of ND-42 in mitochondria and its related biological processes during spermatid elongation. Notably, we demonstrated that ND-42 depletion led to maintenance defects of the major mitochondrial derivative and the minor mitochondrial derivative by affecting mitochondrial membrane potential and mitochondrial-encoded genes. Our study proposes a novel regulatory mechanism of ND-42 for spermatid mitochondrial derivative maintenance, contributing to a better under-standing of spermatid elongation.

Automated summary

During spermatogenesis in Drosophila, mitochondrial elongation is crucial for sperm maturation. However, the regulatory mechanism of spermatid mitochondria during elongation is still not well understood. This study demonstrates that ND-42 is essential for male fertility and spermatid elongation in Drosophila by maintaining mitochondrial function and regulating mitochondrial membrane potential and mitochondrial-encoded genes. The findings provide insights into the regulatory mechanism of spermatid elongation.