Drosophila Tet Is Expressed in Midline Glia and Is Required for Proper Axonal Development

Abstract

Ten-Eleven Translocation (TET) proteins are important epigenetic regulators that play a key role in development and are frequently deregulated in cancer. Drosophila melanogaster has a single homologous Tet gene ( dTet ) that is highly expressed in the central nervous system during development. Here, we examined the expression pattern of dTet in the third instar larval CNS and discovered its presence in a specific set of glia cells: midline glia (MG). Moreover, dTet knockdown resulted in significant lethality, locomotor dysfunction, and alterations in axon patterning in the larval ventral nerve cord. Molecular analyses on dTet knockdown larvae showed a downregulation in genes involved in axon guidance and reduced expression of the axon guidance cue Slit. Our findings point toward a potential role for dTet in midline glial function, specifically the regulation of axon patterning during neurodevelopment.

Drosophila Tet Is Required for Maintaining Glial Homeostasis in Developing and Adult Fly Brains

“…1 E ). This is in line with previously published knock-down experiments of dTet reporting locomotion defects ( Wang et al, 2018 ; Ismail et al, 2019 ). Adult dTet-deficient flies cannot fly or climb and are prone to fall over while walking.…”

“…Co-staining with the pan-neuronal marker Embryonic lethal abnormal vision (ELAV) showed that Tet[MI05009] -G4 is expressed in most neurons of the ventral nerve cord (VNC; L3) and adult central brain ( Fig. 2 B ) similar what has been published for an endogenous dTet -GFP reporter ( Ismail et al, 2019 ). Tet[MI04973]- G4 on the other side, showed less overlap with the neuronal marker ELAV ( Fig.…”

“…2 D ), but was observed with Tet[MI04973]- G4>UAS-nGFP larvae stained with slit. Besides, midline glia expression of dTet has previously been reported using an endogenous dTet-reporter ( Ismail et al, 2019 ). Moreover, there was no overlap detected between Fas2 and dTet reporter expression in adult fly brains, whereas in larval stages, Tet[MI05009] -G4>mCD8GFP brains showed a faint signal in the mushroom body region ( Fig.…”

“…dTet was recently reported to be expressed in midline glia ( Ismail et al, 2019 ), a highly-specialized cell type that is molecularly, functionally and developmentally distinct from other glia and corresponds to a structure in vertebrates called the floor plate ( Jacobs, 2000 ). Here, we confirmed midline glia expression with another dTet reporter ( Fig.…”

“…Similar to mammalian TETs, Drosophila Tet (dTet) has been shown to regulate expression of genes involved in fly neurodevelopment and neuronal function, specifically important for behavior as well as learning and memory ( Yao et al, 2018 ). While dTet expression in fly brains has been mainly linked to neuronal expression during development ( Wang et al, 2018 ), dTet was more recently shown to be expressed in a specific glia population, the midline glial cells, where it plays an important role in axon guidance by controlling the expression level of the repulsive cue slit ( Ismail et al, 2019 ). A clear advantage of the Drosophila system is the lack of functional redundant TET homologs present in the mammalian system.…”