Impaired Heat Shock Response in Cells Expressing Full-Length Polyglutamine-Expanded Huntingtin

The molecular mechanisms by which polyglutamine (polyQ)-expanded huntingtin (Htt) causes neurodegeneration in Huntington's disease (HD) remain unclear. The malfunction of cellular proteostasis has been suggested as central in HD pathogenesis and also as a target of therapeutic interventions for the treatment of HD. We present results that offer a previously unexplored perspective regarding impaired proteostasis in HD. We find that, under non-stress conditions, the proteostatic capacity of cells expressing full length polyQ-expanded Htt is adequate. Yet, under stress conditions, the presence of polyQ-expanded Htt impairs the heat shock response, a key component of cellular proteostasis. This impaired heat shock response results in a reduced capacity to withstand the damage caused by cellular stress. We demonstrate that in cells expressing polyQ-expanded Htt the levels of heat shock transcription factor 1 (HSF1) are reduced, and, as a consequence, these cells have an impaired a heat shock response. Also, we found reduced HSF1 and HSP70 levels in the striata of HD knock-in mice when compared to wild-type mice. Our results suggests that full length, non-aggregated polyQ-expanded Htt blocks the effective induction of the heat shock response under stress conditions and may thus trigger the accumulation of cellular damage during the course of HD pathogenesis

Expression Profiling of Autism Candidate Genes during Human Brain Development Implicates Central Immune Signaling Pathways

The Autism Spectrum Disorders (ASD) represent a clinically heterogeneous set of conditions with strong hereditary components. Despite substantial efforts to uncover the genetic basis of ASD, the genomic etiology appears complex and a clear understanding of the molecular mechanisms underlying Autism remains elusive. We hypothesized that focusing gene interaction networks on ASD-implicated genes that are highly expressed in the developing brain may reveal core mechanisms that are otherwise obscured by the genomic heterogeneity of the disorder. Here we report an in silico study of the gene expression profile from ASD-implicated genes in the unaffected developing human brain. By implementing a biologically relevant approach, we identified a subset of highly expressed ASD-candidate genes from which interactome networks were derived. Strikingly, immune signaling through NFκB, Tnf, and Jnk was central to ASD networks at multiple levels of our analysis, and cell-type specific expression suggested glia—in addition to neurons—deserve consideration. This work provides integrated genomic evidence that ASD-implicated genes may converge on central cytokine signaling pathways

Next-gen sequencing identifies non-coding variation disrupting miRNA-binding sites in neurological disorders

Understanding the genetic factors underlying neurodevelopmental and neuropsychiatric disorders is a major challenge given their prevalence and potential severity for quality of life. While large-scale genomic screens have made major advances in this area, for many disorders the genetic underpinnings are complex and poorly understood. To date the field has focused predominantly on protein coding variation, but given the importance of tightly controlled gene expression for normal brain development and disorder, variation that affects non-coding regulatory regions of the genome is likely to play an important role in these phenotypes. Herein we show the importance of 3 prime untranslated region (3'UTR) non-coding regulatory variants across neurodevelopmental and neuropsychiatric disorders. We devised a pipeline for identifying and functionally validating putatively pathogenic variants from next generation sequencing (NGS) data. We applied this pipeline to a cohort of children with severe specific language impairment (SLI) and identified a functional, SLI-associated variant affecting gene regulation in cells and post-mortem human brain. This variant and the affected gene (ARHGEF39) represent new putative risk factors for SLI. Furthermore, we identified 3'UTR regulatory variants across autism, schizophrenia and bipolar disorder NGS cohorts demonstrating their impact on neurodevelopmental and neuropsychiatric disorders. Our findings show the importance of investigating non-coding regulatory variants when determining risk factors contributing to neurodevelopmental and neuropsychiatric disorders. In the future, integration of such regulatory variation with protein coding changes will be essential for uncovering the genetic causes of complex neurological disorders and the fundamental mechanisms underlying health and disease

Analysis of Chaperone mRNA Expression in the Adult Mouse Brain by Meta Analysis of the Allen Brain Atlas

The pathology of many neurodegenerative diseases is characterized by the accumulation of misfolded and aggregated proteins in various cell types and regional substructures throughout the central and peripheral nervous systems. The accumulation of these aggregated proteins signals dysfunction of cellular protein homeostatic mechanisms such as the ubiquitin/proteasome system, autophagy, and the chaperone network. Although there are several published studies in which transcriptional profiling has been used to examine gene expression in various tissues, including tissues of neurodegenerative disease models, there has not been a report that focuses exclusively on expression of the chaperone network. In the present study, we used the Allen Brain Atlas online database to analyze chaperone expression levels. This database utilizes a quantitative in situ hybridization approach and provides data on 270 chaperone genes within many substructures of the adult mouse brain. We determined that 256 of these chaperone genes are expressed at some level. Surprisingly, relatively few genes, only 30, showed significant variations in levels of mRNA across different substructures of the brain. The greatest degree of variability was exhibited by genes of the DnaJ co-chaperone, Tetratricopeptide repeat, and the HSPH families. Our analysis provides a valuable resource towards determining how variations in chaperone gene expression may modulate the vulnerability of specific neuronal populations of mammalian brain

GREATER SAGE-GROUSE IN THE BI-STATE DISTINCT POPULATION SEGMENT: AN EVALUATION OF GENETIC STRUCTURE, CONNECTIVITY, AND VITAL RATES IN MONO COUNTY, CALIFORNIA

The Bi-State Distinct Population segment (DPS) of greater sage-grouse (Centrocercus urophasianus) is genetically and geographically isolated from populations in other portions of the species range. In 2013, the Bi-State DPS was proposed to receive threatened status under the Endangered Species Act. To aid in conservation of this DPS we evaluated population genetic substructure, dispersal, and vital rates, including female survival, nest success, and brood survival. From 2007-2012, we radio-marked and monitored 112 greater sage-grouse and collected genetic data at 17 microsatellite loci for 334 individuals. We found evidence for 5 genetic populations. With telemetry data we did not document movements between populations but found genetic evidence that 10 individuals were likely recent dispersers. Female seasonal survival was highest during the winter and lowest during the breeding season, ranging from 0.68-0.97. Daily survival rate of nests decreased over the nesting season, ranging from 0.986-0.918. Apparent brood survival ranged from 30-100%.Thesis (M.S., Natural Resources)--University of Idaho, May 201