DYDC1

DYDC1 is a testis-enriched protein that functions in both acrosome biogenesis and flagellar structure during spermiogenesis. It physically interacts with the BAR-domain protein SH3P13, accumulates in the acrosome area during late spermiogenesis, and its knockdown disrupts acrosome formation and spermatid differentiation in mice (PMID:19545932). DYDC1 is also a structural component of the radial spoke 1 (RS1) head and head-neck complex in sperm flagella, where loss of RS1 (in IQUB-deficient sperm) correlates with flagellar beat defects (PMID:39849482).

1. 2009 Medium

   The first functional characterization of DYDC1 established that it interacts with SH3P13, localizes to the acrosome during spermiogenesis, and is required for normal acrosome biogenesis — answering what role this uncharacterized testis-enriched gene plays in male germ cell development.

   Evidence Yeast two-hybrid screen from human testis library, immunolocalization in spermatids, and RNAi knockdown with germ cell transplantation in mice

   PMID:19545932

   Open questions at the time

   • Knockdown phenotype from a single lab has not been independently replicated
   • Molecular mechanism by which DYDC1–SH3P13 interaction drives acrosome formation is undefined
   • Whether DYDC1 loss causes male infertility in a full knockout model was not tested
2. 2025 Medium

   Proteomic dissection of radial spoke composition revealed that DYDC1 is a structural subunit of the RS1 head and head-neck complex in sperm flagella — extending its function beyond acrosome biogenesis to axonemal architecture and motility regulation.

   Evidence Mass spectrometry of IQUB-deficient human and mouse sperm lacking RS1, combined with western blotting and structural modeling

   PMID:39849482

   Open questions at the time

   • Identification is based on loss of DYDC1 in RS1-depleted sperm; direct structural placement within the RS1 complex awaits cryo-EM validation
   • Whether DYDC1 loss alone is sufficient to disrupt RS1 assembly or flagellar motility is untested
   • Relationship between DYDC1's acrosomal and flagellar roles is unexplored

• It remains unknown whether DYDC1 mutations cause human infertility, how its dual localization to the acrosome and radial spoke is regulated, and what its precise molecular activity is within either structure.
• No human disease-causing mutations in DYDC1 have been reported
• No enzymatic or scaffolding activity has been biochemically assigned
• No structural model of DYDC1 at atomic resolution exists