@article {1459, title = {Sequential activation of Notch and~Grainyhead~gives apoptotic competence to Abdominal-B expressing larval neuroblasts in Drosophila Central nervous system [Transgenic Fly Facility]}, journal = {PLoS Genet}, volume = {16}, year = {2020}, month = {2020 Aug 31}, pages = {e1008976}, 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 resident Hox gene Abdominal-A (Abd-A) as an apoptosis trigger, Dsx-negative NBs (in A8-A10 segments) keep the levels of resident Hox gene 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.

}, issn = {1553-7404}, doi = {10.1371/journal.pgen.1008976}, author = {Bakshi, Asif and Sipani, Rashmi and Ghosh, Neha and Joshi, Rohit} } @article {1458, title = {The Hox gene uses Doublesex as a cofactor to promote neuroblast apoptosis in the central nervous system [Transgenic Fly Facility]}, journal = {Development}, volume = {146}, year = {2019}, month = {2019 08 22}, abstract = {

Highly conserved DM domain-containing transcription factors (Doublesex/MAB-3/DMRT1) are responsible for generating sexually dimorphic features. In the central nervous system, a set of Doublesex (Dsx)-expressing neuroblasts undergo apoptosis in females whereas their male counterparts proliferate and give rise to serotonergic neurons crucial for adult mating behaviour. Our study demonstrates that the female-specific isoform of Dsx collaborates with Hox gene () to bring about this apoptosis. Biochemical results suggest that proteins AbdB and Dsx interact through their highly conserved homeodomain and DM domain, respectively. This interaction is translated into a cooperative binding of the two proteins on the apoptotic enhancer in the case of females but not in the case of males, resulting in female-specific activation of apoptotic genes. The capacity of AbdB to use the sex-specific isoform of Dsx as a cofactor underlines the possibility that these two classes of protein are capable of cooperating in selection and regulation of target genes in a tissue- and sex-specific manner. We propose that this interaction could be a common theme in generating sexual dimorphism in different tissues across different species.

}, keywords = {Animals, Apoptosis, DNA-Binding Proteins, Drosophila, Drosophila Proteins, Female, Gene Expression Regulation, Developmental, Genes, Homeobox, Homeodomain Proteins, Male, Neural Stem Cells, Protein Isoforms, Sex Characteristics}, issn = {1477-9129}, doi = {10.1242/dev.175158}, author = {Ghosh, Neha and Bakshi, Asif and Khandelwal, Risha and Rajan, Sriivatsan Govinda and Joshi, Rohit} } @article {683, title = {Combinatorial action of Grainyhead, Extradenticle and Notch in regulating Hox mediated apoptosis in Drosophila larval CNS.}, journal = {PLoS Genet}, volume = {13}, year = {2017}, month = {2017 Oct}, pages = {e1007043}, abstract = {

Hox mediated neuroblast apoptosis is a prevalent way to pattern larval central nervous system (CNS) by different Hox genes, but the mechanism of this apoptosis is not understood. Our studies with Abdominal-A (Abd-A) mediated larval neuroblast (pNB) apoptosis suggests that AbdA, its cofactor Extradenticle (Exd), a helix-loop-helix transcription factor Grainyhead (Grh), and Notch signaling transcriptionally contribute to expression of RHG family of apoptotic genes. We find that Grh, AbdA, and Exd function together at multiple motifs on the apoptotic enhancer. In vivo mutagenesis of these motifs suggest that they are important for the maintenance of the activity of the enhancer rather than its initiation. We also find that Exd function is independent of its known partner homothorax in this apoptosis. We extend some of our findings to Deformed expressing region of sub-esophageal ganglia where pNBs undergo a similar Hox dependent apoptosis. We propose a mechanism where common players like Exd-Grh-Notch work with different Hox genes through region specific enhancers to pattern respective segments of larval central nervous system.

}, keywords = {Amino Acid Sequence, Animals, Apoptosis, Central Nervous System, DNA-Binding Proteins, Drosophila, Drosophila Proteins, Enhancer Elements, Genetic, Female, Gene Expression Regulation, Developmental, Genes, Homeobox, Homeodomain Proteins, Larva, Male, Nuclear Proteins, Receptors, Notch, Transcription Factors}, issn = {1553-7404}, doi = {10.1371/journal.pgen.1007043}, author = {Khandelwal, Risha and Sipani, Rashmi and Govinda Rajan, Sriivatsan and Kumar, Raviranjan and Joshi, Rohit} } @article {684, title = {Role of Homothorax in region specific regulation of Deformed in embryonic neuroblasts.}, journal = {Mech Dev}, volume = {138 Pt 2}, year = {2015}, month = {2015 Nov}, pages = {190-7}, abstract = {

The expression and regulation of Hox genes in developing central nervous system (CNS) lack important details like specific cell types where Hox genes are expressed and the transcriptional regulatory players involved in these cells. In this study we have investigated the expression and regulation of Drosophila Hox gene Deformed (Dfd) in specific cell types of embryonic CNS. Using Dfd neural autoregulatory enhancer we find that Dfd autoregulates itself in cells of mandibular neuromere. We have also investigated the role of a Hox cofactor Homothorax (Hth) for its role in regulating Dfd expression in CNS. We find that Hth exhibits a region specific role in controlling the expression of Dfd, but has no direct role in mandibular Dfd neural autoregulatory circuit. Our results also suggest that homeodomain of Hth is not required for regulating Dfd expression in embryonic CNS.

}, keywords = {Animals, Central Nervous System, Drosophila, Drosophila Proteins, Enhancer Elements, Genetic, Gene Expression Regulation, Developmental, Genes, Homeobox, Homeodomain Proteins, Neural Stem Cells, Organogenesis}, issn = {1872-6356}, doi = {10.1016/j.mod.2015.09.003}, author = {Kumar, Raviranjan and Chotaliya, Maheshvari and Vuppala, Sruthakeerthi and Auradkar, Ankush and Palasamudrum, Kalyani and Joshi, Rohit} }