CHTF18 (chromosome 16 fidelity factor 18) is a component of the CTF18-RFC clamp loader complex that catalyzes ATP-dependent loading of PCNA onto primed and gapped DNA during DNA replication 1. This complex binds single-stranded and primed DNA and has weak ATPase activity stimulated by RPA and PCNA presence [UniProt]. CHTF18 plays critical roles in sister chr16 cohesion, genome stability during leading strand synthesis, and meiotic recombination 2, 3. In spermatogenesis, Chtf18-null males exhibit reduced sperm concentration and defective meiotic recombination with premature homologous chromosome 16 and delayed DNA double-strand break repair 3. Beyond its canonical replication function, CHTF18 has a moonlighting role in hematopoietic stem cell positioning and migration that is independent of its clamp loader activity 4. Disease relevance includes T lymphopenia when CHTF18 function is disrupted 4, male infertility from spermatogenic failure 5, congenital anomalies of kidney and urinary tract (CAKUT) 6, neurodevelopmental delay with epilepsy 7, and endometrial cancer through chromosome 16 8. CHTF18 variants are also associated with prostate cancer prognosis 9. These findings establish CHTF18 as a multifunctional gene critical for chr16 integrity and cell-type-specific developmental processes.