Biology subjects

Bernardo-Garcia, F. J.

Publications and source records attributed to Bernardo-Garcia, F. J..

3 recordsLinked to original sources

bioRxiv2021

Discoidin domain receptor regulates ensheathment, survival, and caliber of peripheral axons

Invertebrate axons and small caliber axons in mammalian peripheral nerves are unmyelinated but still ensheathed by glia. How this type of ensheathment is controlled and its roles in supporting neuronal function remain unclear. Here we use Drosophila wrapping glia, which ensheathe peripheral axons to study the function and development of non-myelinating ensheathment. We developed a new SplitGal4 intersectional driver to target wrapping glia for genetic ablation and found that loss of wrapping glia severely impaired larval locomotor behavior. We performed an in vivo RNAi screen in Drosophila to identify glial genes required for axon ensheathment during development and identified the conserved receptor tyrosine kinase Discoidin domain receptor (Ddr). In larval peripheral nerves, loss of Ddr resulted in severely reduced ensheathment of axons. We found a strong dominant genetic interaction between Ddr and the fly type XV/XVIII collagen Multiplexin (Mp), suggesting Ddr functions a collagen receptor to drive wrapping of axons during development. Surprisingly, despite severe impairment of ensheathment, the residual wrapping in Ddr mutants was sufficient to support basic circuit function during larval stages. In adult nerves, loss of Ddr from glia decreased long-term survival of sensory neurons and significantly reduced axon caliber in an identifiable neuron without overtly affecting ensheathment. Our data establish a crucial role for non-myelinating glia in peripheral nerve development and function across the lifespan, and identify Ddr as a key regulator of axon-glia interactions during ensheathment and nerve growth.

neuroscience↗

bioRxiv2019

Multilevel regulation of the glass locus during Drosophila eye development

Development of eye tissue is initiated by a conserved set of transcripton factors termed retinal determination network (RDN). In the fruit fly Drosophila melanogaster, the zinc-finger transcription factor Glass acts directly downstream of the RDN to control idendity of photoreceptor as well as non-photoreceptors cells. Tight control of spatial and temporal gene expression is a critical feature during development, cell-fate determination as well as maintainance of differentiated tissues. The molecular mechanisms that control expression of glass, however remain largely unknown. We here identify complex regulatory mechanisms controlling expression of the glass locus. All information to recapitulate glass expression are contained in a compact 5.2 kb cis-acting genomic element by combining different cell-type specific and general enhancers with repressor elements. Moreover, the immature RNA of the locus contains an alterantive small open reading frame (smORF) upstream of the actual glass translation start, resulting in a small peptide instead of the three possible glass protein isoforms. CRISPR/Cas9-based mutagenesis shows that the smORF is not required for the formation of functioning photoreceptors, but to attenuate effects of glass misexpression. Furthermore, editing the genome to generate glass loci eliminating either one or two isoforms shows that only one of the three proteins is critical for formation of functioning photoreceptors, while removing the two other isoforms did not cause defects in developmental or photoreceptor function. Our results show that eye development and function is surprisingly robust and appears buffered to targeted manipulations of critical features of the glass transcript, suggesting a strong selection pressure to allow the formation of a functioning eye.

developmental biology↗

bioRxiv2018

Glass confers rhabdomeric photoreceptor identity in Drosophila, but not across all metazoans

Across metazoans, visual systems employ different types of photoreceptor neurons to detect light. These include rhabdomeric PRs, which exist in distantly related phyla and possess an evolutionarily conserved phototransduction cascade. While the development of rhabdomeric PRs has been thoroughly studied in the fruit fly Drosophila melanogaster, we still know very little about how they form in other species. To investigate this question, we tested whether the transcription factor Glass, which is crucial for instructing rhabdomeric PR formation in Drosophila, may play a similar role in other metazoans. Glass homologues exist throughout the animal kingdom, indicating that this protein evolved prior to the metazoan radiation. Interestingly, our work indicates that glass is not expressed in rhabdomeric photoreceptors in the planarian Schmidtea mediterranea nor in the annelid Platynereis dumerilii. Combined with a comparative analysis of the Glass DNA-binding domain, our data suggest that the fate of rhabdomeric PRs is controlled by Glass-dependent and Glass-independent mechanisms in different animal clades.

developmental biology↗