Palmitoyltransferase ZDHHC19 regulates histone-to-protamine exchange during spermiogenesis in mice

Spermiogenesis, the final phase of spermatogenesis, involves replacing histones by protamines, a process known as histone-to-protamine exchange, which is crucial for chromatin condensation. While this exchange is essential, the precise mechanisms remain incompletely understood. In this study, we discovered that the palmitoyltransferase ZDHHC19 functions as a key regulator of mouse spermiogenesis. Loss of Zdhhc19 leads to male infertility and abnormal sperm morphology. Zdhhc19-deficient sperm exhibit impaired histone-to-protamine exchange, leading to retention of histones and misdistribution of protamines. Similarly, the palmitoyltransferase catalytic site mutant Zdhhc19 C142S knock-in mice show reduced fertility, sperm abnormalities, and histone retention. Mechanistically, ZDHHC19 mediates histone H3 palmitoylation at cysteine 110, weakening H3-H4 interactions and reducing its affinity for DNA. Palmitoylation of H3 facilitates histone-to-protamine exchange. This study highlights the essential role of ZDHHC19's palmitoyl-transferase activity in histone-to-protamine exchange during spermiogenesis and underscores the broader significance of histone palmitoylation in chromatin remodeling.

Methods
Haploid spermatids and spermatocytes were sorted by FACS. In brief, adult mouse testes were put in PBS at 33°C for collagenase and trypsin digestion. After filtering, single germ cells were stained with 5 μg/ml Hoechst 33342 at 33°C for 40 min. Then, the two populations were separated and sorted by FACS (BD, Aria II, Influx) according to signals in 630/30 and 460/50 excited by 355nm. 630/30high 460/50high population represents spermatocytes, and 630/30low 460/50low population represents haploid spermatids. In haploid spermatids, the FSChigh population represents round spermatids and the FSClow population represents elongated spermatids.