Transcription factor Pebbled/RREB1 regulates injury-induced axon degeneration

Abstract

Genetic studies of Wallerian degeneration have led to the identification of signaling molecules (e.g., dSarm/Sarm1, Axundead, and Highwire) that function locally in axons to drive degeneration. Here we identify a role for the CH zinc finger transcription factor Pebbled [Peb, Ras-responsive element binding protein 1 (RREB1) in mammals] in axon death. Loss of Peb in glutamatergic sensory neurons results in either complete preservation of severed axons, or an axon death phenotype where axons fragment into large, continuous segments, rather than completely disintegrate. Peb is expressed in developing and mature sensory neurons, suggesting it is required to establish or maintain their competence to undergo axon death. mutant phenotypes can be rescued by human RREB1, and they exhibit dominant genetic interactions with mutants, linking to the axon death signaling cascade. Surprisingly, Peb is only able to fully block axon death signaling in glutamatergic, but not cholinergic sensory neurons, arguing for genetic diversity in axon death signaling programs in different neuronal subtypes. Our findings identify a transcription factor that regulates axon death signaling, and mutant phenotypes of partial fragmentation reveal a genetically accessible step in axon death signaling.

Morphological and Functional Evaluation of Axons and their Synapses during Axon Death in <em>Drosophila melanogaster</em>

“…When these assays are used to specifically study axon death, it is important to note that the phenotype of morphological or functional preservation should be robust over time. There are cases where axon death leads to a consistent yet less pronounced phenotype in morphological preservation 34,35 , and whether such a phenotype translates into functional preservation remains to be determined.…”

A Functional Analysis of theDrosophilaGenehindsight: Evidence for Positive Regulation of EGFR Signaling

“…As part of this work, the authors performed ChIP-seq analysis of a GM2 Drosophila cell line expressing a tagged version of Hnt. This resulted in the identification of 80 potential direct targets of Hnt (Farley et al 2018). Interestingly, several of these putative Hnt target genes are also known targets of the EGFR signaling pathway, including InR ( (Lim et al 2007).…”

“…In pupae, the sensory organ precursors (SOPs) of developing micro-and macrochaetae, as well as myoblasts, and all photoreceptor cells (R cells) of the developing retina express hnt (Pickup et al 2002;Reeves and Posakony 2005;Krejci et al 2009;Buffin and Gho 2010). In the adult, hnt is expressed in the midgut (intestinal stem cells, enteroblasts, and enterocytes), developing egg chambers (follicle cells and the migratory border cells), spermathecae, and in mature neurons of the wing (Sun and Deng 2007;Melani et al 2008;Baechler et al 2015;Shen and Sun 2017;Farley et al 2018).…”

A method for rapid selection of randomly induced mutations in a gene of interest using CRISPR/Cas9 mediated activation of gene expression

“…Confocal imaging of pupal eye made use of Ubi-DE-cadherin-GFP as previously described (20). Complementation crosses were facilitated by the transgenic line peb BAC-CH321-46J02 as described (19). GAL4 > UAS based overexpression of hnt used UAS-GFP-hnt as previously described (21).…”

“…The chromosome used in the mutagenesis screen was w PBac{RB}e02388b (Exelixis at Harvard medical School #e02388). Pre-existing hnt alleles used included hnt XE81 , hnt 1142 , hnt 308 , and hnt 345x as previously described (15,(17)(18)(19). Confocal imaging of pupal eye made use of Ubi-DE-cadherin-GFP as previously described (20).…”