The Dumpy-30 (DPY-30) protein was first described in C. elegans, in which it is involved in dosage compensation of sex chromosomes. Conserved from yeast to humans, the DPY-30 family is involved in gene expression and chromatin modification, specifically histone methylation. DPY-30 and closely related proteins contain a short motif that is related to the dimerization motif in the regulatory subunit of protein kinase A (PKA), which consists of two ?helices that form a four-helix bundle during dimerization. As a member of the DPY-30 family, DYDC1 (DPY30 domain-containing protein 1), also known as DPY30D1 and RSD9, is a 177 amino acid protein that binds to Endophilin III and plays a crucial role during acrosome biogenesis. DYDC1 is specifically expressed in brain and testis and accumulates in the acrosome area during spermatogenesis. Knockdown of DYDC1 mRNA results in disruption of acrosome formation and spermatid differentiation.