KIF18B Is a Cell-Type Specific Regulator of Spindle Orientation in the Epidermis

The document reports that KIF18B, a microtubule catastrophe factor, plays a crucial role in regulating microtubule dynamics to ensure proper spindle orientation in keratinocytes, particularly during mitosis. KIF18B is shown to accumulate at the cell cortex and colocalize with the spindle orientation machinery. The study finds that KIF18B is necessary for oriented cell divisions within the hair placode, which is critical for the initial stage of hair follicle development, but it is not essential in the interfollicular epidermis. Mutations in KIF18B or NuMA, which disrupt spindle orientation in the hair placode, lead to incorrect expression of cell fate markers in hair follicle progenitor cells. This establishes a functional link between spindle orientation and cell fate decisions during hair follicle morphogenesis, highlighting the importance of spindle orientation in asymmetric cell division for determining cell fate.