TDRD7 participates in lens development and spermiogenesis by mediating autophagosome maturation

ABSTRACT

In humans, TDRD7 (tudor domain containing 7) mutations lead to a syndrome combining congenital cataracts (CCs) and non-obstructive azoospermia (NOA), characterized by abnormal lens development and spermiogenesis. However, the molecular mechanism underlying TDRD7’s functions in eye and testicular development are still largely unknown. Here, we show that the depletion of this gene in mice and humans resulted in the accumulation of autophagosomes and the disruption of macroautophagic/autophagic flux. The disrupted autophagic flux in tdrd7-deficient mouse embryonic fibroblasts (MEFs) was caused by a failure of autophagosome fusion with lysosomes. Furthermore, transcriptome analysis and biochemical assays showed that TDRD7 might directly bind to Tbc1d20 mRNAs and downregulate its expression, which is a key regulator of autophagosome maturation, resulting in the disruption of autophagosome maturation. In addition, we provide evidence to show that TDRD7-mediated autophagosome maturation maintains lens transparency by facilitating the removal of damaged proteins and organelles from lens fiber cells and the biogenesis of acrosome. Altogether, our results showed that TDRD7 plays an essential role in the maturation of autophagosomes and that tdrd7 deletion results in eye defects and testicular abnormalities in mice, implicating disrupted autophagy might be the mechanism that contributes to lens development and spermiogenesis defects in human.

Abbreviations: CB: chromatoid bodies; CC: congenital cataract; CTSD: cathepsin D; DMSO: dimethyl sulfoxide; LAMP1: lysosomal-associated membrane protein 1; LECs: lens epithelial cells; MAP1LC3/LC3/Atg8: microtubule-associated protein 1 light chain 3; MEFs: mouse embryonic fibroblasts; NOA: non-obstructive azoospermia; OFZ: organelle-free zone; RG: RNA granules; SQSTM1/p62: sequestosome 1; TBC1D20: TBC1 domain family member 20; TDRD7: tudor domain containing 7; TEM: transmission electron microscopy; WT: wild type.

KEYWORDS:

• Acrosome biogenesis
• autophagy
• lens development
• spermiogenesis
• tbc1d20
• tdrd7

Statistical analysis

The statistical significance of the results was calculated using a Student’s t-test and one-way ANOVA using the SPSS software, version 19.0 (SPSS, Chicago, USA). All the experiments were repeated three times, and a P-value of < 0.05 was considered statistically significant.

Acknowledgments

We thank Xiaoxuan Yang from the Central South University for her experimental assistance including western blotting and EGFR degradation assay. We also thank Xing Wang from Chinese Academy of Sciences for kindly providing scholarly discussions.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the national key research & developmental program of China (2018YFC1004900), the national natural science foundation of China (81771645 and 81971447), the key grant of prevention and treatment of birth defect from Hunan province (2019SK1012), the research grant of CITIC-Xiangya (YNXM-201915, YNXM-201913, YNXM-201912, YNXM-201916), the China Postdoctoral Science Foundation Funded Project (2019M662786), and the Hunan Provincial Natural Science Foundation of China (2020JJ5993).