MTFP1 (mitochondrial fission process 1) is an inner mitochondrial membrane protein that negatively regulates mitochondrial fusion to control mitochondrial dynamics and cellular homeostasis 1. Mechanistically, MTFP1 inhibits inner membrane fusion and recruits DRP1 for fission, thereby isolating damaged membrane subdomains into small MTFP1-enriched mitochondria (SMEM) that undergo autophagic degradation 12. This quality control function is essential for maintaining mtDNA copy number and nucleoid recycling 1. MTFP1 expression is nutrient-regulated through mTORC1-mediated translation, linking environmental stimuli to mitochondrial fission and apoptosis; mTOR inhibition reduces MTFP1 levels, causing mitochondrial hyperfusion and apoptosis 3. PPA2 activates MTFP1-DNM1L fission signaling to control both mitochondrial proliferation and stress-induced mitophagy 4. MTFP1 is transcriptionally regulated by thyroid hormone during stem cell development 5 and by the transcription factor ZBTB48 6. Clinically, MTFP1 dysregulation associates with sarcopenia, where it correlates with muscle wasting severity and serves as a diagnostic biomarker 7. In prostate cancer, MTFP1 shows differential expression between tumor and normal tissues, suggesting potential biomarker utility 8. Loss of MTFP1 function impairs these quality control mechanisms and can trigger apoptosis.