PLK1-mediated phosphorylation of WDR62/MCPH2 ensures proper mitotic spindle orientation

Area of Science:

• Genetics
• Cell Biology
• Developmental Biology

Background:

• Primary microcephaly (MCPH) is a congenital disorder characterized by reduced head circumference.
• Mutations in the WDR62 gene (MCPH2) are a known cause of MCPH.
• The precise molecular mechanisms underlying WDR62-associated microcephaly are not fully understood.

Purpose of the Study:

• To investigate the cellular pathology of microcephaly caused by WDR62 mutations.
• To elucidate the physiological role of WDR62 in cell division and spindle orientation.
• To identify the interaction between WDR62 and other key mitotic regulators.

Main Methods:

• Whole-exome sequencing to identify mutations in a Japanese family with microcephaly.
• CRISPR/Cas9 gene editing to create human cell lines with a specific WDR62 missense mutation (c.731C>T, p.Ser244Leu).
• Microscopy and biochemical assays to analyze mitotic spindle orientation, astral microtubule assembly, and protein phosphorylation.

Main Results:

• WDR62/MCPH2-mutated cells displayed randomized mitotic spindle orientation due to impaired astral microtubule assembly.
• WDR62 was identified as a substrate of Polo-like kinase 1 (PLK1), phosphorylated at Serine 897.
• Phosphorylation of WDR62 by PLK1 at spindle poles is crucial for promoting astral microtubule assembly and stabilizing spindle orientation.

Conclusions:

• The PLK1-WDR62 signaling pathway is essential for maintaining proper mitotic spindle orientation.
• Dysfunctional WDR62, due to mutations, disrupts spindle orientation, potentially contributing to the pathogenesis of primary microcephaly.
• This study provides critical insights into the molecular basis of WDR62-related microcephaly.