DYDC1 (DPY30 domain containing 1) is a testis and brain-expressed protein that plays critical roles in male germ cell development and ciliary function. Functionally, DYDC1 is a structural component of radial spoke 1 (RS1) complexes within axonemes, where it constitutes part of the RS1 head-neck complex alongside NME5, DNAJB13, and PPIL6 1. During spermiogenesis, DYDC1 interacts with the BAR domain-containing protein SH3P13 and accumulates in the acrosome area during late spermatid differentiation, where it plays a crucial role in regulating acrosome biogenesis—the process of forming the sperm acrosome 2. RNA interference studies demonstrate that knockdown of endogenous Dydc1 interferes with acrosome formation and spermatid differentiation 2. Through its role in radial spoke assembly, DYDC1 contributes to regulating sperm flagellar beat frequency and amplitude, as deficiency in RS1 components correlates with reduced sperm kinetic parameters and asthenozoospermia (reduced sperm motility) 1. While DYDC1 was examined as a candidate gene in genetic studies of myofibrillar myopathy and hereditary spastic paraplegia, no disease-causing mutations were identified in these contexts 3. Clinically, DYDC1 dysfunction may contribute to male infertility through impaired spermatogenesis and reduced sperm motility.