The overall goal of this proposal is to elucidate the thiol redox mechanisms that alter neurodevelopment, which can exacerbate cognitive dysfunction in Down syndrome (DS). Down syndrome (DS) is the most common genetic cause of intellectual disability. Importantly, the extent of intellectual disability is highly variable, and parents of affected individuals are often aware of DS during pregnancy. This creates a window of opportunity to improve outcomes through identification of environmental factors and associated mechanisms impacting early development in DS. Preliminary data and reports from our laboratory and others demonstrate that cells from DS individuals exhibit distorted proteostasis, enhanced oxidative stress, and altered metabolism. We hypothesize that these are linked through atypical thiol redox systems in DS cells. This increases vulnerability to thiol-reactive xenobiotics through dysregulation of central carbon metabolism, modifying stem cell fate decisions via altered regulation of Wnt/β-catenin signaling as a mechanism contributing to cognitive dysfunction. Our prior results show that the environmental toxicant, maneb (MB), a neurotoxic dithiocarbamate fungicide, impairs proteostasis, increases oxidative stress and displays greater toxicity in DS cells compared to euploid controls. MB also modifies mitochondrial function, central carbon metabolism and our new preliminary data show that DS cells display significant baseline alterations in the Wnt signaling pathway. Wnt signaling is a vital cell signaling conduit critical for both stem cell maintenance and neurodevelopment. Therefore, elucidating the environmental mechanisms impacting DS development, e.g. Wnt signaling and oxidative stress, will provide a foundation to prioritize environmental chemical surveillance in DS neurodevelopment. Disruption of cellular thiol redox systems, e.g. thiol redox proteome, is a key feature of oxidative stress. This mechanism is also critical for embryonic development, where mitochondrially-derived reactive oxygen species (ROS) trigger stem cells to differentiate. Thus, the approach detailed below will include thiol-reactive toxicants (TRT) as an innovative means to study Gene-Environment interactions affecting neurodevelopment in a special population, DS. This proposal involves three Specific Aims and makes use of a powerful library of euploid and trisomy 21 induced pluripotent stem cells (iPSC) and directed differentiation protocols to investigate the role of thiol redox signaling in the effects of TRT on stem cells derived from DS individuals, and how these exposures alter specific pathways (Wnt and central carbon metabolism) during neurodevelopment. In Specific Aim 1 we will determine if trisomy 21-mediated Wnt dysfunction is exacerbated by TRT exposure, resulting in aberrant iPSC differentiation. Western blotting, qRT-PCR, chemical tools and single cell transcriptomics will be used to interrogate this aim. Specific Aim 2 is designed to study the impact of TRT exposure on the thiol redox proteome and identify mechanistic targets involved in aberrant differentiation. In Specific Aim 3 we will utilize metabolic approaches like metabolomics and extracellular flux analyses to correlate Wnt dysfunction and redox proteomic alterations to metabolic alterations and developmental outcomes. Together, the novel research proposed here will fill a critical gap in knowledge with regard to neurodevelopmental impacts of thiol reactive toxicants in DS and how these exposures can alter neurogenesis, potentially contributing to cognitive variability. Finally, the studies described here are an innovative and data-driven extension of my funded research exploring further into new mechanisms, e.g. Wnt and thiol redox signaling, by which exposures can alter critical neurodevelopmental processes in DS.

PROJECT NARRATIVE Down syndrome, a genetic condition resulting in the triplication of chromosome 21, occurs in 1 in approximately 700 live births in the United States of America. We believe that, due to this genetic condition, Down syndrome patients are more vulnerable to toxic chemicals in the environment, and that these exposures contribute to the variability of intellectual disability observed in this patient population. This project is designed to test this hypothesis.