Systematic analysis of YFP traps reveals common mRNA/protein discordance in neural tissues.

While post-transcriptional control is thought to be required at the periphery of neurons and glia, its extent is unclear. Here, we investigate systematically the spatial distribution and expression of mRNA at single molecule sensitivity and their corresponding proteins of 200 YFP trap lines across the intact Drosophila nervous system. 97.5% of the genes studied showed discordance between the distribution of mRNA and the proteins they encode in at least one region of the nervous system. These data suggest that post-transcriptional regulation is very common, helping to explain the complexity of the nervous system. We also discovered that 68.5% of these genes have transcripts present at the periphery of neurons, with 9.5% at the glial periphery. Peripheral transcripts include many potential new regulators of neurons, glia, and their interactions. Our approach is applicable to most genes and tissues and includes powerful novel data annotation and visualization tools for post-transcriptional regulation.

One-step CRISPR-Cas9 protocol for the generation of plug & play conditional knockouts in Drosophila melanogaster.

This one-step method generates, for any locus, a conditional knockout allele in Drosophila. The allele carries a bright fluorescent marker for easy screening and an attP landing site for subsequent genetic manipulations. After removing the selectable marker with Cre, the attP site can be used to insert DNA fragments expressing tagged or mutant alleles to determine protein localization and function in a tissue- and stage-specific manner. Only a single round of CRISPR-Cas9-mediated editing is required. For complete details on the use and execution of this protocol, please refer to the DWnt4[cKO] example in Yu et al. (2020).

Frizzled-Dependent Planar Cell Polarity without Secreted Wnt Ligands.

Planar cell polarity (PCP) organizes the orientation of cellular protrusions and migratory activity within the tissue plane. PCP establishment involves the subcellular polarization of core PCP components. It has been suggested that Wnt gradients could provide a global cue that coordinates local PCP with tissue axes. Here, we dissect the role of Wnt ligands in the orientation of hairs of Drosophila wings, an established system for the study of PCP. We found that PCP was normal in quintuple mutant wings that rely solely on the membrane-tethered Wingless for Wnt signaling, suggesting that a Wnt gradient is not required. We then used a nanobody-based approach to trap Wntless in the endoplasmic reticulum, and hence prevent all Wnt secretion, specifically during the period of PCP establishment. PCP was still established. We conclude that, even though Wnt ligands could contribute to PCP, they are not essential, and another global cue must exist for tissue-wide polarization.