Sequential activation of Notch and Grainyhead gives apoptotic competence to Abdominal-B expressing larval neuroblasts in Drosophila Central nervous system

PLoS Genet. 2020 Aug 31;16(8):e1008976. doi: 10.1371/journal.pgen.1008976. eCollection 2020 Aug.

Abstract

Neural circuitry for mating and reproduction resides within the terminal segments of central nervous system (CNS) which express Hox paralogous group 9-13 (in vertebrates) or Abdominal-B (Abd-B) in Drosophila. Terminal neuroblasts (NBs) in A8-A10 segments of Drosophila larval CNS are subdivided into two groups based on expression of transcription factor Doublesex (Dsx). While the sex specific fate of Dsx-positive NBs is well investigated, the fate of Dsx-negative NBs is not known so far. Our studies with Dsx-negative NBs suggests that these cells, like their abdominal counterparts (in A3-A7 segments) use Hox, Grainyhead (Grh) and Notch to undergo cell death during larval development. This cell death also happens by transcriptionally activating RHG family of apoptotic genes through a common apoptotic enhancer in early to mid L3 stages. However, unlike abdominal NBs (in A3-A7 segments) which use increasing levels of resident Hox factor Abdominal-A (Abd-A) as an apoptosis trigger, Dsx-negative NBs (in A8-A10 segments) keep the levels of resident Hox factor Abd-B constant. These cells instead utilize increasing levels of the temporal transcription factor Grh and a rise in Notch activity to gain apoptotic competence. Biochemical and in vivo analysis suggest that Abdominal-A and Grh binding motifs in the common apoptotic enhancer also function as Abdominal-B and Grh binding motifs and maintains the enhancer activity in A8-A10 NBs. Finally, the deletion of this enhancer by the CRISPR-Cas9 method blocks the apoptosis of Dsx-negative NBs. These results highlight the fact that Hox dependent NB apoptosis in abdominal and terminal regions utilizes common molecular players (Hox, Grh and Notch), but seems to have evolved different molecular strategies to pattern CNS.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abdomen / growth & development
  • Animals
  • Apoptosis / genetics*
  • Central Nervous System / growth & development
  • DNA-Binding Proteins / genetics*
  • Drosophila Proteins / genetics*
  • Drosophila melanogaster / genetics
  • Drosophila melanogaster / growth & development
  • Female
  • Gene Expression Regulation, Developmental / genetics
  • Larva / genetics
  • Larva / growth & development
  • Male
  • Neural Stem Cells / metabolism
  • Receptors, Notch / genetics*
  • Regulatory Sequences, Nucleic Acid / genetics
  • Transcription Factors / genetics*

Substances

  • DNA-Binding Proteins
  • DSX protein, Drosophila
  • Drosophila Proteins
  • N protein, Drosophila
  • Receptors, Notch
  • Transcription Factors
  • grh protein, Drosophila

Grants and funding

This work was supported by the DBT/Wellcome Trust India Alliance Intermediate Fellowship (Ref: 500171/Z/09/Z) awarded to R.J., Department of Biotechnology, India funding to R.J. (BT/PR26385/MED/122/110/2017 and BT/PR27455/BRB/10/1647/2018); Department of Science and Technology, India funding to R.J. (EMR/2016/003775) and CDFD core funds to R.J. UGC SRF Award to A.B. [UGC Ref No. 22/06/2014(i)EU-V, 2061430472] ICMR SRF Award to R.S. [ICMR Ref.No:3/1/3/JRF-2012/HRD-63 (40260)] ICMR SRF Award to N.G. [ICMR Ref.No: 3/1/3/JRF-2011/HRD-59 (42219)]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.