The LINC complex and microtubule motors regulate the number and position of nuclei in the subperineurial glial cells of the Drosophila blood-brain barrier

Multinucleated cells, or syncytia, provide a unique system in which to understand the mechanisms of cellular organization. The two most dramatic features of syncytial cells are the number of nuclei and the positioning of nuclei within a shared cytoplasm. While the mechanisms that regulate these features have been studied in some syncytial cells, most syncytial cells are uncharacterized. Furthermore, whether the formation of the syncytia and the organization of the syncytia are linked is not known. We have characterized the subperineurial glial cells (SPG) which form the most restrictive layer of the Drosophila blood-brain barrier. We have found that disruption of the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex, Kinesin, or cytoplasmic Dynein specifically in SPG cells affected both SPG cell development and general brain development. Specifically, the brains were smaller in each case and the SPG cells were smaller when the LINC complex or cytoplasmic Dynein were disrupted. The number of nuclei per cell was increased when Kinesin was disrupted, decreased when cytoplasmic Dynein was disrupted, and abnormal numbers of nuclei were found when the LINC complex was disrupted. Finally, the positions of nuclei relative to their nearest neighbor was decreased when the expression of each gene was disrupted and nuclei were closer to the cell edge when either Kinesin or cytoplasmic Dynein were disrupted. Finally, the evenness of nuclear spacing was reduced when LINC complex or Kinesin expression was disrupted. Together, these data illustrate that formation of SPG cells and the organization of SPG cells are dependent on microtubule motors and the LINC complex.