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

描述(申请人提供)：颅咽管综合征(CFNS)是一种以骨骼和神经异常为特征的X连锁神经筛查疾病。CFNS是由EFNB1突变引起的，EFNB1编码ePhin-B1，一种跨膜蛋白，也是Eph/eaffin信号分子家族的成员。与许多X连锁疾病不同的是，EFNB1杂合子丢失的女性比半合子男性受到的影响更严重。这种独特的遗传模式是由于杂合子女性在随机X失活后EFNB1表达的嵌合体。在Efnb1+/-小鼠中，嵌合体导致ePhin-B1表达和非表达细胞之间的活跃细胞分选，导致ePhin-B1表达边界中断，但这种细胞分选发生的机制仍不完全清楚。此外，细胞分选还没有在CFNS的人体模型中得到证实，因此尚不清楚细胞分选是否对疾病病理生理学有重大贡献。CFNS的一个重要临床表现是冠状颅缝融合，即颅骨的额骨和顶骨之间的缝线过早融合。然而，在Efnb1+/-小鼠模型中没有观察到这种表型，这为理解其病因提供了障碍。因此，需要一个人体系统来了解CFNS中冠状颅缝融合的细胞机制。人类诱导多能干细胞(HiPSCs)在人类疾病研究中具有巨大的潜力，因为它们允许将患者特有的细胞分化为与疾病相关的细胞类型，而这些细胞类型通常很难或不可能直接获得。HiPSCs已被用于建立各种发育疾病的模型，但尚未用于建立先天性颅面畸形的模型。我们为CFNS建立了一种新的HiPSC模型，以研究这种疾病的潜在细胞和分子病因，并证明了HiPSC来源的神经上皮细胞经历了Eph/eaffin介导的细胞分选。我建议使用我们的CFNS的HiPSC模型来确定有助于Eph/eaffin介导的细胞分选的途径，以及研究细胞分选如何有助于CFNS的颅突融合。

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.