ZBTB40 is a zinc finger and BTB domain-containing transcription factor with multifaceted roles in telomere biology, bone metabolism, and inflammatory disease. Primary function: ZBTB40 functions as a telomere-associated protein that binds telomeric dsDNA through its BTB/POZ domain to protect telomeres in alternative lengthening of telomeres (ALT) cells 1. ZBTB40 knockout results in telomere dysfunction and excessive lengthening, indicating it negatively regulates ALT-mediated telomere extension 1. Mechanism: In osteoblasts, ZBTB40 directly promotes bone mineralization and osteoblast activity 2. The protein antagonizes the suppressive effects of the long noncoding RNA ZBTB40-IT1 on osteogenesis, with ZBTB40-IT1 inhibiting bone formation via the miR-514a-3p/FOXO4 axis 3. Disease relevance: ZBTB40 genetic variants associate with reduced bone mineral density and osteoporosis susceptibility in both European and Han Chinese populations 4. Loss of ZBTB40 causes male infertility through impaired meiotic DNA repair, compromised double-strand break repair, and sperm morphology defects 5. ZBTB40 variants also increase inflammatory bowel disease (IBD) risk while reducing bone density, suggesting shared genetic mechanisms between these diseases 6. In myeloid cells, ZBTB40 regulates calprotectin expression, connecting it to IBD pathogenesis 7. Clinical significance: ZBTB40 represents a target for treating osteoporosis and male infertility, and may inform IBD-related bone loss management.