Dual roles of IQCG, a novel microtubule nucleation factor rapidly evolving in humans

The centrosome serves as the main microtubule-organizing structure, playing crucial roles in animal development. Uncovering new components and elucidating their functions helps to understand the regulation of cell maintenance and division by the centrosome. In this study, through a combination of genetic analyses and cell biological characterizations, we identify IQ Motif Containing G (IQCG) as a novel microtubule nucleation factor with a dual role involved in both centrosomal microtubule organization and mitotic spindle formation. IQCG interacts with GSK3β via its N2 region, enhancing its centrosomal accumulation in interphase; subsequently, IQCG disperses into the spindle to promote microtubule generation during mitosis and ensure robust cell division. Furthermore, our analyses indicate that the IQCG gene has undergone accelerated evolution within the human lineage, with positive selection acting on the variable N2 region. This adaptation may confer advantages to human cells by augmenting central regulatory control over cellular activities through the centrosome. Our findings offer novel insights into the functional mechanisms and evolutionary significance of the human centrosome associated with human evolution. Summary blurb The cellular functions of the novel microtubule nucleation factor IQCG, which enhances centrosomal microtubule organization and cell division robustness, are implicated in human evolution.