# ATF4 Is Dispensable for Spermatogenesis but Protective Against ER Stress Under Normal Conditions

## TL;DR

ATF4 is not needed for sperm production but helps protect testicular function during stress.

## Contribution

Shows ATF4 is not essential for spermatogenesis but supports proteostasis under ER stress in male germ cells.

## Key findings

- ATF4 deletion in germ cells did not affect fertility or testicular structure.
- ATF4 maintains testicular proteome stability, especially through the ER stress pathway.
- ATF4 acts as a resilience factor under ER stress but not a direct regulator of spermatogenesis.

## Abstract

Male spermatogenesis is highly sensitive to intrinsic and extrinsic environmental stress. ATF4, an essential regulator of the cellular stress reaction, is thought to contribute to maintaining reproductive health, yet its specific role in male germ cells remained unclear. In this study, we investigated whether Atf4 plays a role in normal spermatogenesis by creating a mouse model that lacks Atf4, specifically in germ cells. However, these mice showed normal fertility and no obvious defects in sperm development or testicular structure. Surprisingly, proteomic analysis revealed that ATF4 contributes to maintaining the expression of endoplasmic reticulum (ER) stress-related proteins. These findings suggest that ATF4 is unlikely to directly regulate spermatogenesis but rather acts as a protective agent in mediating stress responses. These findings suggest that ATF4 acts as a potential protective agent that affects sperm survival and safeguards testicular function under ER stress.

Spermatogenesis is a metabolically intensive process that is highly sensitive to perturbations in proteostasis. The integrated stress response (ISR) and its central effector, ATF4, orchestrate adaptive responses to maintain cellular homeostasis under stress; however, the functional significance of ATF4 in mammalian spermatogenesis has not been established. To investigate this, we engineered a conditional knockout mouse model with germ cell-specific deletion of the Atf4 gene. Results showed that Atf4 deletion did not impair spermatogenesis or male fertility, with knockout mice exhibiting normal testicular histology and standard sperm parameters. Proteomic analysis, however, revealed that ATF4 contributes to testicular protein expression homeostasis, as its deficiency caused marked dysregulation of the testicular proteome, especially impacting SQSTM1/p62 downregulate through endoplasmic reticulum (ER) stress pathway. We conclude that ATF4’s role in regulating proteostatic balance is functionally decoupled from its necessity for the core progression of spermatogenesis. These findings define ATF4 as a potential resilience agent safeguarding testicular function under ER stress, rather than a direct regulator of male germ cell development.