A central role for R7bp in the regulation of itch sensation.

Itch is a protective sensation producing a desire to scratch. Pathologic itch can be a chronic symptom of illnesses such as uremia, cholestatic liver disease, neuropathies and dermatitis, however current therapeutic options are limited. Many types of cell surface receptors, including those present on cells in the skin, on sensory neurons and on neurons in the spinal cord, have been implicated in itch signaling. The role of G protein signaling in the regulation of pruriception is poorly understood. We identify here 2 G protein signaling components whose mutation impairs itch sensation. R7bp (a.k.a. Rgs7bp) is a palmitoylated membrane anchoring protein expressed in neurons that facilitates Gαi/o -directed GTPase activating protein activity mediated by the Gß5/R7-RGS complex. Knockout of R7bp diminishes scratching responses to multiple cutaneously applied and intrathecally-administered pruritogens in mice. Knock-in to mice of a GTPase activating protein-insensitive mutant of Gαo (Gnao1 G184S/+) produces a similar pruriceptive phenotype. The pruriceptive defect in R7bp knockout mice was rescued in double knockout mice also lacking Oprk1, encoding the G protein-coupled kappa-opioid receptor whose activation is known to inhibit itch sensation. In a model of atopic dermatitis (eczema), R7bp knockout mice showed diminished scratching behavior and enhanced sensitivity to kappa opioid agonists. Taken together, our results indicate that R7bp is a key regulator of itch sensation and suggest the potential targeting of R7bp-dependent GTPase activating protein activity as a novel therapeutic strategy for pathological itch.

An Eye on Trafficking Genes: Identification of Four Eye Color Mutations in Drosophila.

Genes that code for proteins involved in organelle biogenesis and intracellular trafficking produce products that are critical in normal cell function . Conserved orthologs of these are present in most or all eukaryotes, including Drosophila melanogaster Some of these genes were originally identified as eye color mutants with decreases in both types of pigments found in the fly eye. These criteria were used for identification of such genes, four eye color mutations that are not annotated in the genome sequence: chocolate, maroon, mahogany, and red Malpighian tubules were molecularly mapped and their genome sequences have been evaluated. Mapping was performed using deletion analysis and complementation tests. chocolate is an allele of the VhaAC39-1 gene, which is an ortholog of the Vacuolar H+ ATPase AC39 subunit 1. maroon corresponds to the Vps16A gene and its product is part of the HOPS complex, which participates in transport and organelle fusion. red Malpighian tubule is the CG12207 gene, which encodes a protein of unknown function that includes a LysM domain. mahogany is the CG13646 gene, which is predicted to be an amino acid transporter. The strategy of identifying eye color genes based on perturbations in quantities of both types of eye color pigments has proven useful in identifying proteins involved in trafficking and biogenesis of lysosome-related organelles. Mutants of these genes can form the basis of valuable in vivo models to understand these processes.

Improving the specificity and efficacy of CRISPR/CAS9 and gRNA through target specific DNA reporter.

Genomic engineering by the guide RNA (gRNA)-directed CRISPR/CAS9 is rapidly becoming a method of choice for various biological systems. However, pressing concerns remain regarding its off-target activities and wide variations in efficacies. While next generation sequencing (NGS) has been primarily used to evaluate the efficacies and off-target activities of gRNAs, it only detects the imperfectly repaired double strand DNA breaks (DSB) by the error-prone non-homologous end joining (NHEJ) mechanism and may not faithfully represent the DSB activities because the efficiency of NHEJ-mediated repair varies depending on the local chromatin environment. Here we describe a reporter system for unbiased detection and comparison of DSB activities that promises to improve the chance of success in genomic engineering and to facilitate large-scale screening of CAS9 activities and gRNA libraries. Additionally, we demonstrated that the tolerances to mismatches between a gRNA and the corresponding target DNA can occur at any position of the gRNA, and depend on both specific gRNA sequences and CAS9 constructs used.