Elucidating the role of centrosomal proteins during meiotic DNA repair

During meiosis in males, completion of homologous chromosome recombination and synapsis are prerequisites to centriole duplication and centrosome separation. In oocytes, centrosomes are lost during meiotic prophase and remain absent until fertilization. However, the role of the centrosome in early prophase oocytes remains poorly understood. Polo-like Kinase 4 (PLK4) is predominantly known for driving centriole duplication during mitosis. During meiosis, PLK4 localizes to both the centrosome and to unsynapsed chromosomes, implicating PLK4 as a novel regulator that coordinates homologous chromosome recombination and synapsis with centrosome dynamics. Our hypothesis is further supported by our assessment of Plk4I242N/+ mutant germ cells. Plk4I242N/+ spermatocytes have aberrancies in meiotic recombination events, including elevated crossover (CO) precursor foci (MLH1/MLH3), which result in mid-prophase arrest and apoptosis. Similar defects are observed in spermatocytes lacking the centrosomal protein CEP63 (Cep63Gt/Gt), and these defects are epistatic with the Plk4I242N/+ mutation. We have also shown that both Plk4I242N/+ and Cep63Gt/Gt mutant oocytes have increased MLH1 foci. However, Plk4I242N/+ and Cep63Gt/Gt oocytes do not arrest, and instead form unresolved CO-like structures in late prophase that impede homologous chromosome desynapsis. We observed that aberrant CO-like structures persist in Plk4I242N/+ oocytes lacking a functional MLH1/3-dependent CO pathway (Mlh3-/-, Plk4I242N/+). This genetic assay revealed that chromosome structural abnormalities observed in Plk4I242N/+ oocytes likely arise prior to deposition of MLH1/3 dimers. Moreover, analysis of Plk4I242N/+ oocytes revealed evidence of perturbed chromosome movements and abnormalities in localization of various Linker of Nucleoskeleton and Cytoskeleton (LINC) complex components. Collectively, our observations suggest that PLK4 coordinates centrosome-mediated chromosome movements with homologous chromosome recombination and synapsis in male and female germ cells