Genomics and functional dissection of fetal brain abnormalities using a prenatal cohort

摘要 胎儿脑异常（FBA）是最常见的产前超声检查异常之一， 约占出生缺陷的20%，对卫生保健系统造成巨大负担。FBA可分离 或综合征，并具有巨大的表型异质性。产前诊断的配对方法 通过基因分析确定病因病变的超声表征异常表型的方法已经得到改进， 能够准确地就诊断、预后和复发风险向家属提供咨询。最近，产前 外显子组测序（ES）已应用于致死性或多个胎儿异常的情况下，以确定 分子诊断，否则无法确定与传统的测试。我们的小组和其他使用ES的人 在多胎儿畸形病例中的诊断率为23.6%，但在孤立的FBA中仅为2.6 异常，表明需要提高FBA的诊断能力。我们认为， 未解决的胎儿病例是由于我们对产前基因型的理解存在差距， FBA和群体遗传学的局限性，以建立新的候选基因中罕见变异的因果关系。我们 在产前遗传诊断和人类疾病的体内斑马鱼建模方面处于最前沿的团队将 克服目前诊断产前FBA的挑战。我们将在外显子组和基因组范围内 与相关模型系统（斑马鱼）的变化。 我们假设我们将1）产生初步发现 通过在斑马鱼中建模新的候选FBA基因直接与人脑发育相关;以及2） 使用全基因组测序（WGS）和深度表型分析改进FBA产前诊断。我们将：1. 使用分层分析法对200多例临床确诊的FBA胎儿及其父母进行生物信息学分析。 对已经可用的亲本-胎儿三外显子组数据的过滤策略2.对114例前瞻性入组的患者进行WGS 胎儿及其父母与全面的产前和产后表型数据配对， 表征FBA的基因型/表型; 3.确定候选基因与FBA发育的相关性， 在斑马鱼中使用基因组编辑和表型分析工具确定变异致病性。我们的工作将扩大 了解人类大脑发育的分子过程，建立一个临床研究 混合平台易于应用于FBA和通过胎儿成像可检测的其他解剖缺陷， 异常FBA发育的动物模型，具有将来用于治疗靶点鉴定的潜力。我们 立即的结果将改善产前诊断的FBA的咨询/管理，并导致未来的工作， 为FBA开发新的治疗和预防策略。

ABSTRACT Fetal brain abnormalities (FBA) are one of the most common prenatal sonographic abnormality detected and account for ~20% of birth defects posing a substantial burden on the health care system. FBA can be isolated or syndromic and have vast phenotypic heterogeneity. The paired approach of prenatal diagnosis using ultrasound to characterize aberrant phenotypes with genetic analysis to determine causal lesions has improved the ability to accurately counsel families about diagnosis, prognosis, and recurrence risk. Recently, prenatal exome sequencing (ES) has been applied in cases of lethal or multiple fetal abnormalities to determine a molecular diagnosis that otherwise could not be identified with traditional testing. Our group and others using ES have shown a diagnostic rate of 23.6% in cases of multiple fetal abnormalities, but only 2.6% in isolated FBA abnormalities, indicating a need to improve diagnostic capabilities for FBA. We posit that the overabundance of unresolved fetal cases is due to a gap in our understanding of the repertoire of genotypes underlying prenatal FBA and limitations of population genetics to establish causality of rare variants in novel candidate genes. Our team who is at the forefront of prenatal genetic diagnostics and in vivo zebrafish modeling of human disease will overcome the current challenges of diagnosing prenatal FBA. We will intersect exome- and genome-wide variation with a relevant model system (zebrafish). We hypothesize that we will 1) generate initial discoveries directly relevant to human brain development by modeling novel candidate FBA genes in zebrafish; and 2) improve prenatal diagnosis for FBA using whole genome sequencing (WGS) and deep phenotyping. We will: 1. Perform bioinformatic analysis of 200+ clinically ascertained fetuses with FBA and their parents using a tiered filtering strategy on already available parent-fetus trio exome data 2. Perform WGS on 114 prospectively enrolled fetuses and their parents paired with comprehensive prenatal and postnatal phenotypic data to further characterize genotype/phenotype of FBA; 3. Establish relevance of candidate genes to FBA development and determine variant pathogenicity using genome-editing and phenotyping tools in zebrafish. Our work will expand the understanding of molecular processes governing human brain development, establish a clinical-research hybrid platform readily applicable to FBA and other anatomical defects detectable by fetal imaging, build an animal model of aberrant FBA development with potential for future use in therapeutic target identification. Our immediate results will improve counseling/management of prenatally diagnosed FBA and lead to future work to develop novel therapeutic and preventative strategies for FBA.