Choroid plexus defects in Down syndrome brain organoids enhance neurotropism of SARS-CoV-2. Choroid plexus defects in Down syndrome brain organoids enhance neurotropism of SARS-CoV-2

Why individuals with Down Syndrome (DS, trisomy 21) are particularly susceptible to SARS-CoV-2 induced disease remains largely unclear. The choroid plexus secrets the cerebrospinal fluid and strongly expresses the ACE2 receptor and the chromosome 21 encoded TMPRSS2 protease. To investigate the role of the choroid plexus in SARS-CoV-2 central nervous system infection in DS, we established a new type of brain organoid from DS and isogenic euploid control iPSC that consists of a core of appropriately patterned functional cortical neuronal cell types that is surrounded by a patent and functional choroid plexus (CPCOs). Remarkably, DS-CPCOs not only recapitulated abnormal features of DS cortical development but also revealed defects in ciliogenesis and epithelial cell polarity of the developing choroid plexus. We next demonstrate that the choroid plexus layer facilitates SARS-CoV-2 replication and infection of cortical neuronal cells, and that this is increased in DS-CPCOs. We further show that inhibition of TMPRSS2 activity in DS-CPCOs inhibits SARS-CoV-2 infectivity. We conclude that CPCOs are a useful model for dissecting the role of the choroid plexus in euploid and DS forebrain development and enables screening for therapeutics that can inhibit SARS-CoV-2 induced neuro-pathogenesis. Overall design: Comparative gene expression profiling analysis of RNA-seq data for euploid (EU79) and down syndrome (DS) brain organoids with Choroid plexus (CP) upon infection with SARS-CoV-2.

为何唐氏综合征（Down Syndrome, DS，即21三体综合征）患者尤其易感染严重急性呼吸综合征冠状病毒2型（SARS-CoV-2）并引发相关疾病，目前尚未完全阐明。脉络丛（choroid plexus）可分泌脑脊液，且高表达ACE2受体与21号染色体编码的TMPRSS2蛋白酶。为探究脉络丛在唐氏综合征患者SARS-CoV-2中枢神经系统感染中的作用，我们从唐氏综合征患者及同倍体对照的诱导多能干细胞（induced pluripotent stem cell, iPSC）中构建了一类新型脑类器官：该类器官以经过恰当模式化的功能性皮层神经元细胞群为核心，外围被开放且具备功能的脉络丛包裹，即脉络丛脑类器官（CPCOs）。

值得注意的是，DS-CPCOs不仅重现了唐氏综合征皮层发育的异常特征，还揭示了发育中脉络丛的纤毛发生与上皮细胞极性缺陷。后续实验证实，脉络丛层可促进SARS-CoV-2对皮层神经元细胞的复制与感染，且该效应在DS-CPCOs中更为显著。我们进一步发现，抑制DS-CPCOs中的TMPRSS2活性可降低SARS-CoV-2的感染性。

综上，我们认为CPCOs是可用于剖析同倍体及唐氏综合征前脑发育中脉络丛作用的有效模型，同时能够用于筛选可抑制SARS-CoV-2诱导的神经病理过程的治疗药物。

总体实验设计：对感染SARS-CoV-2后带有脉络丛的同倍体（EU79）与唐氏综合征（DS）脑类器官的RNA测序（RNA-seq）数据开展比较基因表达谱分析。