A CRISPR-engineered Isogenic Model Reveals Altered Neuronal Phenotypes of the 22q11.2 A-B Syndromic Deletion

The 22q11.2 deletion syndrome (22q11.2DS) is the most common copy number variant (CNV)-associated syndrome, leading to congenital and neuropsychiatric anomalies. Patient-derived, induced pluripotent stem cell (iPS) models have provided important insight into the mechanisms of phenotypic features of this condition. However, patient-derived iPSC models may harbor underlying genetic heterogeneity that can confound analysis of pathogenic CNV effects. Furthermore, the ~1.5 Mb “A-B” deletion at this locus is inherited at higher frequency than the more common ~2.7 Mb “A-D” deletion, but remains under-studied due to lack of relevant models. To address these issues, here we leveraged a CRISPR-based strategy in Cas9-expressing iPS cells to engineer novel isogenic models of the 22q11.2 “A-B” deletion. After in vitro differentiation to excitatory neurons, integrated transcriptomic and cell surface proteomics identified deletion-associated alterations in surface adhesion markers. Furthermore, implantation of iPS-derived neuronal progenitor cells into the cortex of neonatal mice found decreased proliferation and accelerated neuronal maturation within a relevant microenvironment. Taken together, our results suggest potential pathogenic mechanisms of the 22q11.2 “A-B” deletion in driving neuronal and neurodevelopmental phenotypes. We further propose that the isogenic models generated here will provide a unique resource to study this less-common variant of the 22q11.2 microdeletion syndrome.

22q11.2缺失综合征（22q11.2DS）是最常见的与拷贝数变异（CNV）相关的综合征，可引发先天性异常与神经精神异常。源自患者的诱导多能干细胞（iPS）模型为解析该疾病表型特征的发病机制提供了重要见解。然而，患者来源的iPS模型可能携带潜在的遗传异质性，这会干扰对致病性CNV效应的分析。此外，该位点约1.5 Mb的‘A-B’缺失的遗传频率高于更为常见的约2.7 Mb的‘A-D’缺失，但由于缺乏相关模型，该缺失类型的研究仍较为匮乏。为解决上述问题，本研究在表达Cas9的诱导多能干细胞中应用基于CRISPR的基因编辑策略，构建了新型的22q11.2‘A-B’缺失同基因模型。在体外分化为兴奋性神经元后，整合的转录组学与细胞表面蛋白质组学分析鉴定出了与缺失相关的表面黏附标志物改变。进一步将iPS来源的神经前体细胞植入新生小鼠皮层后，研究发现在相关微环境中，细胞增殖能力下降且神经元成熟加速。综上，本研究结果提示了22q11.2‘A-B’缺失驱动神经元与神经发育表型的潜在致病机制。我们进一步提出，本研究构建的同基因模型将为研究22q11.2微缺失综合征中这一较为罕见的变异类型提供独特的研究资源。