Prenatal Treatment of Down Syndrome to Improve Brain Development and Neurocognition

National Human Genome Research Institute

Investigators

Linked publications & trials

Abstract

During the past year, we achieved the following progress towards our goals and objectives: 1) Molecular and cellular phenotyping of induced pluripotent stem cells (iPSCs) and iPSC-derived neural progenitor cells (NPCs) from individuals with T21 and age- and sex-matched euploid individuals. We generated a novel, genetically diverse panel of age- and sex-matched T21 and euploid induced pluripotent stem cells (iPSCs) and NPCs for in vitro modeling. Our panel of racially diverse cell lines is larger than those used in previous NPC studies, thus providing the ability to ascertain phenotypic and transcriptomic variability across a diverse dataset. To gain better insights into the molecular mechanisms underlying atypical brain development in fetuses with DS, we performed transcriptome analyses on fibroblasts, and both transcriptome and proteome analyses on iPSCs and NPCs. Additional assays were performed to measure cellular growth, mitochondrial function, oxidative stress and antioxidant capacity. We found that T21 cell lines showed reduced proliferation, increased oxidative stress, and spontaneous cellular senescence relative to euploid controls. We also observed that T21 NPCs showed inter-individual variability in growth rates, oxidative stress, senescence characteristics, and gene and protein expression. This work has been published. 2) Screening of NPCs for therapeutic responses to drugs identified using the Connectivity Map (CMap) database, Library of Integrated Network-Based Cellular Signatures (LINCS) database, or published literature. We propose that T21 NPCs can serve as an in vitro model system to analyze brain differences in DS and may help to identify safe therapeutic molecules for prenatal therapies to improve neurocognition in DS. In particular, analysis of T21 gene expression signatures paired with bioinformatics tools, such as the Connectivity map (Cmap) and the Library of Integrated Network-Based Cellular Signatures (LINCS), may reveal genes and pathways that are relevant to therapeutic intervention. The Cmap and LINCS databases contain small molecule-induced gene expression signatures that can be queried with dysregulated transcriptome signatures to predict drugs that may rescue altered gene expression. We used T21 and euploid NPC transcriptome data to query CMap and LINCS for safe drug candidates that are predicted to rescue T21-associated transcriptomic changes. We also examined previously published drugs that are of interest in the field of DS research. Promising candidates are being further examined for anti-inflammatory effects in mouse macrophages and microglia, in collaboration with Nigel H Greig, PhD (National Institute on Aging). During the past year, promising candidate drugs were also examined for their global transcriptomic effects in T21 NPCs by RNA-Seq analysis. 3) Molecular, cellular and behavioral phenotyping of mouse models of DS to discover phenotypes in each model that recapitulate those present in DS, with an emphasis on the embryo and placenta because of our interests in the prenatal time period. We previously completed deep phenotyping across the lifespan of four mouse models of DS: Dp(16)1/Yey, Ts65Dn, Ts1Cje, and Ts66Yah. These models are trisomic for overlapping mouse chromosome 16 (Mmu16) regions that are orthologous to Hsa21 but are cytogenetically distinct from each other. Interestingly, these four mouse models each exhibit distinct prenatal gene expression and postnatal phenotypes, however, they share several dysregulated pathways that could be targeted in future prenatal therapies, including neuroinflammation, interferon signaling, and oxidative stress response. We are particularly interested in understanding the effects of T21 on the placenta, and the potential for the targeted correction of atypical, T21-associated placental phenotypes to result in improved fetal development. The phenotypic effects of T21 on the placenta are understudied in mouse models of DS. To discover the molecular and cellular mechanisms of atypical placental development, we have performed gene expression and protein expression analyses in the Dp(16)1/Yey, Ts65Dn, Ts1Cje, and Ts66Yah mouse models of DS, with particular focus on the roles of two genes that are trisomic in T21, amyloid beta precursor protein (App) and superoxide dismutase 1 (Sod1). In collaboration with Sebastian Ilianes, MD (Universidad de Los Andes, Chile), we have obtained a collection of placental samples from full-term, live born infants with DS along with euploid controls. Phenotypic and gene expression analyses of these samples are ongoing. (4) Administration of promising candidate drugs to mouse model(s) of DS and evaluation of their safety and efficacy. Our comprehensive analyses of four mouse models of DS suggested that Ts66Yah is the most promising model for placental, embryonic, and candidate drug response studies. Studies on promising drug candidates from our NPC screens will begin once the previous goals are accomplished.