Cerebellar hypoplasia and chromosome elimination in mouse models of Down syndrome

项目摘要/摘要 小脑发育不良可能导致唐氏综合征患者特定症状的认知和适应障碍。 这影响了美国超过25万人。Ts65Dn唐氏小鼠模型的建立 综合征反映了唐氏综合症患者中观察到的几种重要的小脑表型， 包括总体积减少和颗粒细胞密度减少。在小脑皮质发育过程中， 颗粒细胞前体细胞在有丝分裂原Sonic Hedgehog的刺激下增殖。分离的颗粒细胞前体细胞 来自Ts65Dn的小鼠在用Sonic Hedgehog处理时增殖低于对照细胞，单剂量的 Sonic Hedgehog激动剂SAG在出生后第一天拯救小脑形态和一些 Ts65Dn小鼠的学习障碍。然而，目前还不清楚哪些三体基因参与了对Sonic的抑制。 刺猬依赖的增殖。了解三体如何导致小脑发育不全和其他 发育表型对于建立改善唐氏综合症的易处理药物靶点至关重要-- 相关的认知缺陷。因此，我们假设特定三体基因的过度表达 在小脑发育过程中负向调节内源性Sonic Hedgehog途径。我们会 通过在一系列体外筛查中过表达人类21号染色体基因来解决这一假设 确定抑制Sonic Hedgehog信号的候选对象。在这些屏幕中确定的候选人和 在发育中的小脑中都有表达，在初级颗粒细胞前体中也会过度表达。我们会 还优化了CRISPR/Cas9介导的非整倍体细胞系染色体消除技术 来自唐氏综合症的小鼠模型。唐氏病小鼠模型的诱导性染色体消除 综合征将为检测三体引起的表型的发育起源提供一种方法。 总而言之，这个项目的成功完成将为人类如何过度表达提供新的见解 21号染色体基因在小脑发育过程中抑制了对Sonic Hedgehog的反应，并将产生 一个强大的工具，以确定剂量失衡如何作用于唐氏综合症的表型。

Project Summary/Abstract Cerebellar hypoplasia may contribute to syndrome-specific cognitive and adaptive deficits in Down syndrome, which affects more than a quarter million individuals in the United States. The Ts65Dn mouse model of Down syndrome reflects several important cerebellar phenotypes observed in individuals with Down syndrome, including reduced total volume and reduced granule cell density. During development of the cerebellar cortex, granule cell precursors proliferate in response to the mitogen Sonic hedgehog. Granule cell precursors isolated from Ts65Dn mice proliferate less than control cells when treated with Sonic hedgehog, and a single dose of the Sonic hedgehog agonist, SAG, on the first day after birth rescues cerebellar morphology and some learning deficits in Ts65Dn mice. However, it is unknown which trisomic genes contribute to inhibition of Sonic hedgehog-dependent proliferation. Understanding how trisomy causes cerebellar hypoplasia and other developmental phenotypes is critical to establishing tractable drug targets for ameliorating Down syndrome- associated cognitive deficits. Therefore, we hypothesize that the overexpression of specific trisomic genes negatively regulates the endogenous Sonic hedgehog pathway during cerebellar development. We will address this hypothesis by overexpressing human chromosome 21 genes in a series of in vitro screens to identify candidates that inhibit Sonic hedgehog signaling. Candidates that are identified in these screens and are expressed in the developing cerebellum will be overexpressed in primary granule cell precursors. We will also optimize a technique for CRISPR/Cas9-mediated chromosome elimination in aneuploid cell lines derived from a mouse model of Down syndrome. Inducible chromosome elimination in a mouse model of Down syndrome would provide a method for detecting the developmental origins of phenotypes caused by trisomy. Together, successful completion of this project will yield new insights into how overexpression of human chromosome 21 genes dampen response to Sonic hedgehog during cerebellar development and will produce a powerful tool for identifying how dosage imbalance acts to produce phenotypes in Down syndrome.