Synthetic lethal screening in the mammalian central nervous system identifies Gpx6 as a modulator of Huntington’s disease

Huntington’s disease, the most common inherited neurodegenerative disease, is characterized by a dramatic loss of deep-layer cortical and striatal neurons, as well as morbidity in midlife. Human genetic studies led to the identification of the causative gene, huntingtin. Recent genomic advances have also led to the identification of hundreds of potential interacting partners for huntingtin protein and many hypotheses as to the molecular mechanisms whereby mutant huntingtin leads to cellular dysfunction and death. However, the multitude of possible interacting partners and cellular pathways affected by mutant huntingtin has complicated efforts to understand the etiology of this disease, and to date no curative therapeutic exists. To address the general problem of identifying the disease-phenotype contributing genes from a large number of correlative studies, here we develop a synthetic lethal screening methodology for the mammalian central nervous system, called SLIC, for synthetic lethal in the central nervous system. Applying SLIC to the study of Huntington’s disease, we identify the age-regulated glutathione peroxidase 6 (Gpx6) gene as a modulator of mutant huntingtin toxicity and show that overexpression of Gpx6 can dramatically alleviate both behavioral and molecular phenotypes associated with a mouse model of Huntington’s disease. SLIC can, in principle, be used in the study of any neurodegenerative disease for which a mouse model exists, promising to reveal modulators of neurodegenerative disease in an unbiased fashion, akin to screens in simpler model organisms.National Institute of Neurological Disorders and Stroke (U.S.) (Award R01NS085880)William N. and Bernice E. Bumpus Foundation (Early Career Investigator Innovation Award)JPB FoundationEuropean Molecular Biology Organization (Long-term Fellowship

Boundary conditions for the maintenance of memory by PKMζ in neocortex

We report here that ZIP, a selective inhibitor of the atypical protein kinase C isoform PKMζ, abolishes very long-term conditioned taste aversion (CTA) associations in the insular cortex of the behaving rat, at least 3 mo after encoding. The effect of ZIP is not replicated by a general serine/threonine protein kinase inhibitor that is relatively ineffective toward PKMζ, is independent of the intensity of training and the perceptual quality of the taste saccharin (conditioned stimulus, CS), and does not affect the ability of the insular cortex to re-encode the same specific CTA association again. The memory trace is, however, insensitive to ZIP during or immediately after training. This implies that the experience-dependent cellular plasticity mechanism targeted by ZIP is established following a brief time window after encoding, consistent with the standard period of cellular consolidation, but then, once established, does not consolidate further to gain immunity to the amnesic agent. Hence, we conclude that PKMζ is not involved in short-term CTA memory, but is a critical component of the cortical machinery that stores long- and very long-term CTA memories

Differential excitatory vs inhibitory SCN expression at single cell level regulates brain sodium channel function in neurodevelopmental disorders

The four voltage-gated sodium channels SCN1/2/3/8A have been associated with heterogeneous types of developmental disorders, each presenting with disease specific temporal and cell type specific gene expression. Using single-cell RNA sequencing transcriptomic data from humans and mice, we observe that SCNIA is predominantly expressed in inhibitory neurons. In contrast, SCN2/3/8A are profoundly expressed in excitatory neurons with SCN2/3A starting prenatally, followed by SCN1/8A neonatally. In contrast to previous observations from low resolution RNA screens, we observe that all four genes are expressed in both excitatory and inhibitory neurons, however, exhibit differential expression strength. These findings provide molecular evidence, at single-cell resolution, to support the hypothesis that the excitatory/inhibitory (E/I) neuronal expression ratios of sodium channels are important regulatory mechanisms underlying brain homeostasis and neurological diseases. Modulating the Ell expression balance within cell types of sodium channels could serve as a potential strategy to develop targeted treatment for Nay-associated neuronal developmental disorders. (C) 2019 Published by Elsevier Ltd on behalf of European Paediatric Neurology Society

Distinct subnetworks of the thalamic reticular nucleus

The thalamic reticular nucleus (TRN), the major source of thalamic inhibition, regulates thalamocortical interactions that are critical for sensory processing, attention and cognition1–5. TRN dysfunction has been linked to sensory abnormality, attention deficit and sleep disturbance across multiple neurodevelopmental disorders6–9. However, little is known about the organizational principles that underlie its divergent functions. Here we performed an integrative study linking single-cell molecular and electrophysiological features of the mouse TRN to connectivity and systems-level function. We found that cellular heterogeneity in the TRN is characterized by a transcriptomic gradient of two negatively correlated gene-expression profiles, each containing hundreds of genes. Neurons in the extremes of this transcriptomic gradient express mutually exclusive markers, exhibit core or shell-like anatomical structure and have distinct electrophysiological properties. The two TRN subpopulations make differential connections with the functionally distinct first-order and higher-order thalamic nuclei to form molecularly defined TRN–thalamus subnetworks. Selective perturbation of the two subnetworks in vivo revealed their differential role in regulating sleep. In sum, our study provides a comprehensive atlas of TRN neurons at single-cell resolution and links molecularly defined subnetworks to the functional organization of thalamocortical circuits.NIH/NIMH (Grants R01NS098505, R01NS113245)NIH (Grants R01NS098505, R01MH107680