Abstract of the funded parent grant: Numerous cerebellar malformations have been described in humans. Most cause cognitive, in addition to motor and sensory integration deficits. Surprisingly little is understood regarding the developmental basis of these malformations, particularly since little human specific data is available for normal or abnormal fetal cerebellar development. This proposal seeks to advance knowledge of human cerebellar development and malformations using human fetal samples and mouse models. The human-specific data will directly test the validity of our working mouse-derived hypotheses regarding the causes these disorders and strengthen the foundation of normal developmental data which will inform our ongoing genetic analyses of human cerebellar malformations. We will conduct the first in-depth analysis of normal human fetal cerebellar development from 4-23 Gestational Weeks, covering major developmental events. We will then examine the pathology of human fetal Dandy-Walker malformation the most common human cerebellar malformation, affecting ~1/3000 live births. Mouse models will be generated in conjunction with these experiments to assess the mechanisms of the developmental pathology. Finally, we will generate the first transcriptome data for normal human fetal cerebellar neurons. These cell-type specific data are critically missing from current publicly available brain resources. Our human fetal cerebellar neuron data will be compared to transcriptome data from existing datasets of endogenous mouse developing cerebellar neurons as well as mES and hPSC-derived cerebellar neurons to development to assess their validity as model systems. Further, the data will also be integrated with exome data from human cerebellar malformation patients to facilitate gene discovery for these important and understudied birth defects. Abstract of Requested Supplement: This application is being submitted for PA-19-056 in accordance with NOT-OD-19-071. The purpose of this research supplement is to define the cellular, molecular and morphological cerebellar developmental trajectories in human Down Syndrome samples. Developmental profiles will be generated through a combination of single cell sequencing, histological and immunohistochemical analyses and complemented with cell culture assays defining the mitogenic properties of cerebellar granule progenitors. Data from Down Syndrome samples will then be directly compared to profiles from normal and Dandy-Walker malformation developmental cerebellar samples available in the lab and generated under the parent R01. Cerebellar hypoplasia is one of the most consistent phenotypes in Down Syndrome patients that is a significant contributor to neurological phenotypes in these patients. Yet, very little is understood about the developmental disruption of cerebellar development that underlies the congenital hypoplasia. We will produce a multi-modal description of human cerebellar development in Down Syndrome, comparable to data we are already generating to define normal cerebellar development. An understanding how and when Down Syndrome cerebellar developmental trajectories differ from normal and other cerebellar malformations will elucidate the cellular and circuit underpinnings of pediatric and adult Down Syndrome neurological phenotypes. The studies are of high impact with considerable translational potential to identify new therapeutic approaches for neurological deficits in Down Syndrome. They will also generate baseline data human data to the developmental stage-, cell type-, and molecular-specificity of model systems (hiPSCs, organoids, animal models). These experiments specifically address Component 1 and Component 2 of the INCLUDE Project research objectives.

PUBLIC HEALTH RELEVANCE: Cerebellar hypoplasia is one of the most consistent phenotypes in Down Syndrome patients with a strong relationship existing between reduced cerebellar volume and neurological features. Although central to the clinical picture in these patients, surprisingly very little human data is available regarding cerebellar development in Down Syndrome. We will extend our funded studies of normal cerebellar development to include a Down Syndrome cohort to define the molecular and cellular and circuit underpinnings of pediatric and adult Down Syndrome neurological features.