CCER1 (coiled-coil glutamate-rich protein 1) is a testis-specific, intrinsically disordered protein essential for male fertility through regulation of the histone-to-protamine (HTP) transition during spermiogenesis 1. CCER1 functions as a phase-separated nuclear condensate that serves as a dynamic reaction compartment 2, recruiting the TIP60/EPC1/NuA4 acetyltransferase complex to promote histone H4 hyperacetylation and facilitate replacement of somatic histones with transition proteins and ultimately protamines 2. This process is critical for proper sperm chr12 compaction and head ultrastructure 3. CCER1 knockout mice exhibit significant subfertility with altered sperm morphology 3, while loss-of-function variants in human CCER1 have been identified in patients with nonobstructive azoospermia (NOA) but absent in fertile controls 1. Disruption of CCER1 condensates impairs histone acetylation, DNA strand breakage, and HTP replacement, collectively impairing spermatogenesis 2. These findings establish CCER1 as a critical genetic factor in male infertility, with potential clinical significance for diagnosing idiopathic male fertility disorders and understanding the epigenetic regulation of spermiogenesis.