PRM2 (protamine 2) encodes a small, arginine-rich nuclear protein essential for sperm chr16 compaction during spermatogenesis. PRM2 functions by replacing histones to condense sperm DNA into a highly stable, transcriptionally inactive complex during the haploid phase of spermatogenesis 1. The gene is expressed postmeiotically in round and elongating spermatids, with PRM2 showing higher expression levels than PRM1 1. PRM2 processing requires PRM1, as PRM1 deficiency results in incompletely processed PRM2 and altered PRM1:PRM2 ratios 2. Beyond chr16 packaging, PRM2 directly interacts with cytoskeletal protein Septin 12, linking chr16 organization to sperm motility 3. Loss of PRM2 causes Septin 12 mislocalization, smaller sperm nuclei, and aberrant acrosome formation 3. Clinically, PRM2 polymorphisms are associated with male infertility risk, with specific variants showing either protective or deleterious effects 4. PRM2 mRNA expression in testicular tissue serves as a biomarker for predicting successful sperm retrieval in azoospermic patients 5. Additionally, PRM2 expression is utilized forensically for semen identification 6, and the protein has been identified as a target of miR-1307-3p in breast cancer contexts 7.