Defining the cellular mechanisms of craniosynostosis in a human induced pluripotent stem cell model of craniofrontonasal syndrome

DESCRIPTION（由申请人提供）：颅额鼻综合征（CFNS）是一种以骨骼和神经异常为特征的x连锁神经系统疾病。CFNS是由编码ephrin - b1的EFNB1突变引起的，ephrin - b1是一种跨膜蛋白，是Eph/ephrin信号分子家族的成员。与许多x连锁疾病不同，雌性杂合子的EFNB1缺失比半合子的雄性更严重。这种独特的遗传模式是由于在杂合雌性中随机X失活后EFNB1表达的嵌合体。在Efnb1+/-小鼠中，嵌合导致ephrin-B1表达细胞和非表达细胞之间的活跃细胞分选，导致ephrin-B1表达边界中断，但这种细胞分选发生的机制尚不完全清楚。此外，细胞分选尚未在CFNS的人类模型中得到证实，因此尚不清楚细胞分选是否对疾病病理生理有显著贡献。CFNS的一个重要临床表现是冠状颅缝闭塞，或颅骨额骨和顶骨之间的缝合线过早融合。然而，在Efnb1+/-小鼠模型中未观察到这种表型，这为了解其病因提供了障碍。因此，需要一个人体系统来了解CFNS冠状颅缝闭合的细胞机制。人类诱导多能干细胞（hiPSCs）在人类疾病研究中具有巨大潜力，因为它们允许将患者特异性细胞分化为通常难以或不可能直接获得的疾病相关细胞类型。hiPSCs已被用于模拟各种发育性疾病，但尚未用于模拟先天性颅面异常。我们开发了一种新的hiPSC模型来研究CFNS的潜在细胞和分子病因，并证明hiPSC衍生的神经上皮细胞经历了Eph/ephrin介导的细胞分选。我建议使用我们的CFNS的hiPSC模型来确定促进Eph/ephrin介导的细胞分选的途径，并研究细胞分选如何促进CFNS的颅缝闭合。

DESCRIPTION (provided by applicant): Craniofrontonasal syndrome (CFNS) is an X-linked neurocristopathy characterized by skeletal and neurological anomalies. CFNS is caused by mutations in EFNB1, which encodes EPHRIN-B1, a transmembrane protein and member of the Eph/ephrin family of signaling molecules. Unlike many X-linked conditions, females heterozygous for loss of EFNB1 are more severely affected than hemizygous males. This unique inheritance pattern is due to mosaicism for EFNB1 expression after random X inactivation in heterozygous females. In Efnb1+/- mice, mosaicism leads to active cell sorting between ephrin-B1 expressing and non-expressing cells, resulting in disrupted ephrin-B1 expression boundaries, but the mechanism by which this cell sorting occurs remains incompletely understood. Moreover, cell sorting has not been demonstrated in a human model for CFNS, and it is therefore unknown whether or not cell sorting contributes significantly to disease pathophysiology. One clinically important manifestation of CFNS is coronal craniosynostosis, or premature fusion of the suture between the frontal and parietal bones of the skull. This phenotype is not observed in the Efnb1+/- mouse model, however, presenting an obstacle to understanding its etiology. A human system is therefore needed to understand cellular mechanisms underlying coronal craniosynostosis in CFNS. Human induced pluripotent stem cells (hiPSCs) hold great potential for the study of human disease, as they allow differentiation of patient-specific cells into disease-relevant cell types, which are often difficut or impossible to obtain directly. hiPSCs have been used to model a wide variety of developmental diseases, but they have not been used to model congenital craniofacial anomalies. We have developed a novel hiPSC model for CFNS to study the underlying cellular and molecular etiologies of the disorder and have demonstrated that hiPSC-derived neuroepithelial cells undergo Eph/ephrin-mediated cell sorting. I propose to use our hiPSC model of CFNS to determine the pathways that contribute to Eph/ephrin-mediated cell sorting as well as to study how cell sorting contributes to craniosynostosis in CFNS.