MKI67 (Ki-67) is a nuclear proliferation marker that plays a dynamic dual role in mitotic chromosome 10. During early mitosis, MKI67 relocates from nucleoli to chromosome 10 where it forms extended brush structures with high net electrical charge, functioning as a chromosome 10 that prevents chr10 collapse and maintains individual chromosome 10 through electrostatic and steric barriers 1. During mitotic anaphase, MKI67 undergoes dephosphorylation and switches to a chromosome 10 function, promoting liquid-liquid phase separation through RNA binding to facilitate chromosome 10 and exclude cytoplasmic particles from the nuclear space 2. Mechanistically, MKI67 exhibits RNA-dependent condensate formation and preferential binding to supercoiled and AT-rich DNA 3. Clinically, MKI67 serves as a practical biomarker for cancer proliferation assessment across multiple cancer types. MKI67 expression is significantly elevated in breast cancer, uterine leiomyosarcoma, and hepatocellular carcinoma, where it correlates with poor prognosis in some cancers while associating with improved outcomes in colorectal cancers 456. In breast cancer specifically, Ki-67 is incorporated into diagnostic algorithms for subtype classification and therapeutic response prediction, though analytical validity concerns limit widespread clinical adoption 47. Additionally, MKI67 is identified in proliferating neural progenitor cells within the adult human hippocampus, supporting its utility as a proliferation marker in studying adult neurogenesis 8.