Spatial Variation in Cortex Glia Cell Cycle Supports Central Nervous System Organization in Drosophila

Cortex glia (CG) in the ventral nerve cord (VNC) utilize mechanisms such as endocycling and acytokinetic mitosis to increase their nuclear count and support neighboring neural cells. However, the regulation of their cell cycle is not well understood. Our study examines larval development and reveals that CG nuclei in the thoracic region (tVNC) undergo successive rounds of replication and division, exponentially increasing their number to form a syncytial network around neural cells. In contrast, nuclei in the abdominal region (aVNC) only enhance their DNA content by endocycling. Key regulators, including cyclins and cyclin-dependent kinases, are vital for managing replication and division in CG. Notably, the M-phase regulator String ( stg ) is crucial for maintaining diploidy in tVNC nuclei and facilitating syncytial network formation. We demonstrate that ectopic stg expression can induce nuclear division in hyperploid aVNC CG. This study highlights regulatory mechanisms in CG, emphasizing the importance of region-specific cell cycle regulation for nervous system organization.