Project description:During the development of the Drosophila central nervous system the process of midline crossing is orchestrated by a number of guidance receptors and ligands. Many key axon guidance molecules have been identified in both invertebrates and vertebrates, but the transcriptional regulation of growth cone guidance remains largely unknown. One open question is whether transcriptional regulation plays a role in midline crossing, or if local translation can account for the necessary fine tuning of protein levels. To investigate this issue, we conducted a genome wide analysis of transcription in Drosophila embryos using wild type and a number of well-characterized Drosophila guidance mutants and transgenics. We also analyzed a publicly available microarray time course of Drosophila embryonic development with an axon guidance focus. Using hopach, a novel clustering method which is well suited to microarray data analysis, we identified groups of genes with similar expression patterns across guidance mutants and transgenics. We then systematically characterized the resulting clusters with respect to their relevance to axon guidance using two complementary controlled vocabularies: the Gene Ontology (GO) and anatomical annotations of the Atlas of Pattern of Gene Expression (APoGE) in situ hybridization database. The analysis indicates that regulation of gene expression does play a role in the process of axon guidance in Drosophila. We also find a strong link between axon guidance and hemocyte migration, a result that agrees with mounting evidence that axon guidance molecules are co-opted in vertebrate vascularization. Cell cyclin activity in the context of axon guidance is also suggested from our array data. RNA and protein patterns of cell cyclin in axon guidance mutants and transgenics support this possible link. This study provides important insights into the regulation of axon guidance in vivo and suggests that transcription does play a role in control of axon guidance. Keywords: Mutant Analysis
Project description:During the development of the Drosophila central nervous system the process of midline crossing is orchestrated by a number of guidance receptors and ligands. Many key axon guidance molecules have been identified in both invertebrates and vertebrates, but the transcriptional regulation of growth cone guidance remains largely unknown. One open question is whether transcriptional regulation plays a role in midline crossing, or if local translation can account for the necessary fine tuning of protein levels. To investigate this issue, we conducted a genome wide analysis of transcription in Drosophila embryos using wild type and a number of well-characterized Drosophila guidance mutants and transgenics. We also analyzed a publicly available microarray time course of Drosophila embryonic development with an axon guidance focus. Using hopach, a novel clustering method which is well suited to microarray data analysis, we identified groups of genes with similar expression patterns across guidance mutants and transgenics. We then systematically characterized the resulting clusters with respect to their relevance to axon guidance using two complementary controlled vocabularies: the Gene Ontology (GO) and anatomical annotations of the Atlas of Pattern of Gene Expression (APoGE) in situ hybridization database. The analysis indicates that regulation of gene expression does play a role in the process of axon guidance in Drosophila. We also find a strong link between axon guidance and hemocyte migration, a result that agrees with mounting evidence that axon guidance molecules are co-opted in vertebrate vascularization. Cell cyclin activity in the context of axon guidance is also suggested from our array data. RNA and protein patterns of cell cyclin in axon guidance mutants and transgenics support this possible link. This study provides important insights into the regulation of axon guidance in vivo and suggests that transcription does play a role in control of axon guidance. Experiment Overall Design: Several mutants and transgenics were analyzed, totalizing 17 distinct conditions. Individual descriptions are included in each microarray. For each condition there are 3 or 4 replicates. The file's name indicates the replicates, e.g., comm.a reflects the replicate a of mutant commissureless. The experiment design covers a range of mutants and transgenics of key axon guidance mutans, in different dosages. The protocol was the standard Affymetrix protocol.
Project description:We have discovered subsets of axon guidance molecules and transcription factors that are enriched in specific subsets of olfactory sensory neurons. We have demonstrated guidance activity for three of the candidate axon guidance genes we identified, suggesting that this approach is an efficient method for characterizing guidance systems relevant to olfactory axon targeting.
Project description:In the developing spinal cord, Sonic hedgehog (Shh) attracts commissural axons toward the floor plate. How Shh regulates the cytoskeletal remodeling that underlies growth cone turning is unknown. We found that Shh-mediated growth cone turning requires the activity of Docks, which are unconventional GEFs. Knockdown of Dock3 and 4, or their binding partner ELMO1 and 2, abolished commissural axon attraction by Shh in vitro. Dock3/4 and ELMO1/2 were also required for correct commissural axon guidance in vivo. Polarized Dock activity was sufficient to induce axon turning, indicating that Docks are instructive for axon guidance. Mechanistically, we show that Dock and ELMO interact with Boc, the Shh receptor, and that this interaction is reduced upon Shh stimulation. Furthermore, Shh stimulation translocates ELMO to the growth cone periphery and activates Rac1. This identifies Dock/ELMO as an effector complex of non-canonical Shh signaling and demonstrates the instructive role of GEFs in axon guidance.
Project description:Application of single-cell sequencing technology "10X" to obtain neural retinal transcriptomes. This resource highlight transcriptional sequences that establish the hierarchical ordering of early cell fate specification in the retina.
Project description:Ten-eleven translocation (Tet) is an important gene in neurodevelopment, but how Tet regulates brain development is still under study. Mutations in human TET proteins have been found in individuals with neurodevelopmental disorders. Here we report a new function of Tet in regulating Drosophila early brain development. We found that mutation on the Tet DNA-binding domain (TetAXXC) resulted in axon guidance defects in the mushroom body (MB). Tet is required in early brain development during the outgrowth of MB β axons. Transcriptomic study of TetAXXC mutant and wild-type pupal brains shows that glutamine synthetase 2 (Gs2), a key enzyme in glutamatergic signaling, is the most significantly down-regulated gene in the Tet mutant brains. RNAi knockdown or CRISPR/Cas9 mutagenesis of Gs2 recapitulates the TetAXXC phenotype. Surprisingly, Tet and Gs2 act in the insulin-producing cells (IPCs) to control MB axon guidance, and overexpression of Gs2 in the IPCs rescue the axonal defects of TetAXXC. Treating TetAXXC with the metabotropic glutamate receptor antagonist MPEP can also rescue the phenotype confirming Tet function in regulating glutamatergic signaling. TetAXXC and the Drosophila homolog of Fragile X Messenger Ribonucleoprotein protein mutant (Fmr13) have similar mushroom body axonal defects and reduction in Gs2 transcription, and, importantly, overexpression of Gs2 in the IPCs of Fmr1 mutants also rescues the axonal defects. Our studies reveal a new function of Tet in regulating axon guidance in the brain via glutamatergic signaling and suggest overlapping functions between Tet and Fmr1.