The CNS Midline Cells Coordinate Proper Cell Cycle Progression and Identity Determination of the Drosophila Ventral Neuroectoderm

Abstract

The CNS midline cells, specified by the single-minded (sim) gene, are required for the proper patterning of the ventral CNS and epidermis, which are derived from the Drosophila ventral neuroectoderm. Defects in the sim mutant are characterized by the loss of the gene expression, which is required for the proper formation of the ventral neurons and epidermis, and by a decrease in the spacing of longitudinal and commissural axon tracks. Molecular and cellular mechanisms for these defects were analyzed to elucidate the precise role of the CNS midline cells in proper patterning of the ventral neuroectoderm during embryonic neurogenesis. These analyses showed that the ventral neuroectoderm in the sim mutant fails to carry out its proper formation and characteristic cell division cycle. This resulted in the loss of the dividing neuroectodermal cells that are located ventral to the CNS midline. The CNS midline cells are also required for the cell cycle-independent expression of the neural and epidermal markers. This indicates that the CNS midline cells are essential for the establishment and maintenance of the ventral epidermal and neuronal cell lineage by cell-cell interaction. On the other hand, the CNS midline cells do not cause extensive cell death in the ventral neuroectoderm. This study indicates that the CNS midline cells play important roles in the coordination of the proper cell cycle progression and the correct identity determination of the adjacent ventral neuroectoderm along the dorsoventral axis.

CNS midline cells influence the division and survival of lateral glia in the Drosophila nervous system

“…The importance of midline cells in the maintenance of the DV patterning and in proper cell division of NBs in the VNE have been previously shown (Chang et al, 2000;Kim et al, 2005). Considering the results obtained from this study together with the previous results, CNS midline cells play important roles in DV patterning of the VNE, proper division of neurons and lateral glia, correct axon pathway formation, migration, and survival of lateral glia along the axonal tracts.…”

Cell Death as a Regulator of Cerebellar Histogenesis and Compartmentation

“…Is a helix-loop-helix protein expressed in Drosophila CNS midline cells; it coordinates proper cell cycle progression and identity determination; sim is not expressed in parasagittal compartments within the cerebellar cortex [148]; Allen Brain Atlas Mid1 (midline 1) Is a microtubule associated protein that causes midbrain/cerebellar boundary defects within the anterior vermis after misspecification [149] Fxyd7…”

CNS midline cells contribute to maintenance of the initial dorsoventral patterning of theDrosophila ventral neuroectoderm

“…Previous studies have indicated that the Drosophila CNS midline cells act as signaling centers activating EGFR signaling required for correct identity determination, proper cell division, and differentiation of the ventral neuroectoderm (Kim and Crews, 1993;Raz and Shilo, 1993;Golembo et al, 1996;Menne et al, 1997;Lee et al, 1999;Yu et al, 1999;Chang et al, 2000;reviewed by Crews, 1998). However, it was not known whether the midline cells were involved in the initial dorsoventral patterning prior to or during NB formation (Skeath, 1998;Udolph et al, 1998;Yagi et al, 1998).…”