PHTF1 (putative homeodomain transcription factor 1) is an evolutionarily conserved gene located at chromosome 1-p13 that encodes an integral membrane protein with a putative homeodomain 1. The gene is primarily expressed in testis 1, where PHTF1 protein localizes to endoplasmic reticulum domains in maturing male germ cells during meiosis and spermiogenesis 2. PHTF1 interacts with FEM1B (feminization factor homolog) through its amino-terminal region, and this interaction recruits FEM1B to the endoplasmic reticulum membrane 3. Beyond reproductive function, PHTF1 has emerging disease relevance in autoimmune and cardiovascular conditions. Polymorphisms in the PHTF1-PTPN22 region (rs2476601, rs6679677) are associated with type 1 diabetes susceptibility 45, with rs6679677 showing significant risk association in European populations 5. In childhood cancer survivors, a novel locus at 1p13.2 (rs6689879) near PHTF1 associates with therapy-related cardiomyopathy, with PHTF1 promoter hypomethylation observed in affected individuals and upregulation in doxorubicin-induced cardiomyopathy models 6. PHTF1 also appears in pleiotropic genetic analyses linking osteoporosis and rheumatoid arthritis susceptibility 78. These findings suggest PHTF1 participates in immune regulation and cardiac stress responses beyond its established reproductive roles.