2008 — 2011 |
Gray, Jason D |
F31Activity Code Description: To provide predoctoral individuals with supervised research training in specified health and health-related areas leading toward the research degree (e.g., Ph.D.). |
Role of Lrp6 in the Regulation of Wnt Signaling During Brain Development @ Weill Medical College of Cornell Univ
[unreadable] DESCRIPTION (provided by applicant): Neural tube defects (NTD) observed in the naturally occurring mutant mouse line Crooked tail (Cd) were recently shown by this laboratory to be associated with a missense mutation in the low density lipoprotein receptor 6 (Lrp6) gene, which encodes a coreceptor acting with Frizzled (Fz) in the wingless (Wnt) pathway. Wnt binding through Lrp6/Fz activates a [unreadable]-catenin dependent signaling cascade (canonical) to affect TCF/LEF driven gene transcription and regulate numerous developmental processes, including neurulation. The Cd mutation results in hyperactive Wnt canonical signaling that cannot be inhibited by Dkk1, an antagonist of the Wnt pathway. While Lrp6 is most closely associated with canonical signaling, Wnt can also work through B-catenin independent routes (non-canonical), such as the planar cell polarity pathway (PCP). Noncanonical pathways affect changes in the cytoskeleton and thereby regulate cell polarity. Recently, PCP genes have been associated with NTDs in mouse and Xenopus. This proposal seeks to determine whether Lrp6 impacts neural tube closure through canonical or non-canonical Wnt signaling pathways. Either result would identify presently unrecognized Lrp6 functions, i.e. the ability of canonical Wnt signaling to regulate neurulation, the ability of Lrp6 to impact non-canonical pathways, or a possible Wnt signaling independent function for Lrp6. The morphological cause of failed neural tube closure in Cd and Lrp6-- mice will be examined using static and dynamic imaging, as well as immunohistochemistry and in situ hybridization. Non-canonical signaling will be examined by the Wnt dependent activation of small GTPases (Rho, Rac1, and Cdc42) in Cd and Lrp6-- mouse embryonic fibroblast (MEF) cells. Genetic crosses of Cd and Lrp6-- mice with mouse lines carrying deletions of other genes in the Wnt signaling pathway (Fz3) and canonical Wnt reporters (BatGal) will test the Wnt dependence of the neurulation defect and identify whether Lrp6 impacts NTDs primarily through the canonical or non-canonical pathway.Relevance to public health: Neural tube defects, such as spina bifida and anencephaly, affect 0.5 to 1 per thousand infants, and complex genetic interactions underlie their occurrence. This proposal will further characterize the function of the Lrp6 gene, which has been associated with neural tube defects, to advance our understanding of its potential action in clinical populations. Since Wnt signaling is also important in postnatal brain development, the knowledge gained from studying Lrp6 in neural tube development will also benefit patients suffering from mental retardation, autism and other behavior and mood disorders. [unreadable] [unreadable]
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1 |
2014 — 2016 |
Gray, Jason D |
F32Activity Code Description: To provide postdoctoral research training to individuals to broaden their scientific background and extend their potential for research in specified health-related areas. |
Genetic and Environmental Factors That Alter Stress Resilience and Behavior
DESCRIPTION (provided by applicant): Stress in the environment can lead to the development of a mood disorder. Yet, not everyone exposed to a stressful event develops a mood disorder. This suggests that mood disorders result from a unique confluence of genetic and environmental factors. While some factors have been identified that can increase susceptibility to mood disorders, the mechanisms underlying normal recovery after stress (resilience) or failure to recover (loss of resilience) remain unknown. This proposal will use rodent models of chronic restraint stress (CRS) and early life stress (ELS), which have been shown to alter mood-related behaviors and induce morphological and functional changes in the hippocampus to study recovery from stress as a model of susceptibility to mood disorders. The CA3 region of hippocampus is particularly sensitive to the effects of both CRS and ELS, therefore a novel transgenic reporter mouse in which EGFP has been fused to the L10a ribosomal subunit under control of a CA3-specific promoter (Gprin3) will be used to isolate in vivo translating RNA from CA3 neurons. Use of RNA-sequencing technology will allow for high-throughput analysis of gene expression changes implicated in neuroplasticity after CRS, recovery from CRS, and ELS in this highly dynamic subpopulation of neurons. These results will provide a map of altered gene function in normal resilience and impaired resilience, identifying genes that normally recover after CRS, but fail to recover when CRS is combined with ELS. Changes in expression will be correlated with the altered behavioral endpoints expected after ELS. Additionally, this proposal will use a genetic model of increased susceptibility to stress and mood disorders, the BDNF-Val66Met mouse, to study impaired resilience. This mutation in brain derived neurotrophic factor (BDNF) results in the substitution of a valine for a methionine in codon 66 (Val66Met). In clinical populations, carriers of the Met allele exhibit decreased hippocampal function and increased risk of mood disorders. Further, Met allele carriers exposed to ELS have reduced hippocampal volumes and altered BDNF levels as adults. The mouse model of this mutation exhibits anxiety and depression-like behaviors believed to recapitulate the human phenotype and is more vulnerable to CRS, but the effects of ELS on Val66Met mice have not been investigated. This study will use the Val66Met mice in combination with the CA3-reporter mice previously described to investigate the impact of a genetic predisposition to mood disorders on gene expression in CA3. Double transgenic mice will be subjected to ELS and CRS, combining genetic and environmental susceptibilities, to study their impact on gene expression in CA3 neurons as well as the still uncharacterized behavioral effects of ELS on BDNF-Val66Met mice. These experiments will identify genes that fail to recover after CRS, as a result of this highly prevalent genetic mutation, when compared with expression patterns from normal recovery. These gene expression profiles will provide new insight into BDNF's function in stress-induced neuroplasticity and identify new targets for the treatment of mood disorders.
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0.903 |