伴皮层下囊肿的巨脑性白质脑病GLIALCAM突变患者临床遗传学及影像学研究

目的分析GLIALCAM突变伴皮层下囊肿的巨脑性白质脑病(megalencephalic leukoencephalopathy with subcortical cysts,MLC)患儿临床遗传学及头颅影像学特征,为准确的遗传咨询和产前诊断打下基础。方法收集6例MLC先证者及家系临床资料,评估患儿头颅MRI,靶向捕获二代测序行GLIALCAM突变检测,分析影像学特征与基因型关系。结果患儿多具有巨颅及典型MLC头颅MRI改变,伴智力运动发育迟缓、倒退及孤独症样行为,临床诊断MLC。6例患儿发现4个错义突变,c.274C>T(p.Arg92Trp),c.275G>C(p.Arg92Pro),c.203A>T(p.Lys68Met)和c.395C>A(p.Thr132Asn),其中c.275G>C(p.Arg92Pro)为未报道新突变,5例患儿为杂合突变,1例患儿复合杂合突变,Pt2-Pt5突变遗传自母亲,Pt6遗传自表型正常的父母。5例患儿均出现大脑皮层下白质弥漫性异常信号伴肿胀,1例患儿出现好转。结论GLIALCAM突变MLC患者多具有巨颅和典型头颅MRI表现,GLIALCAM突变显性遗传患者头颅MRI具有异质性,部分患儿头颅MRI可恢复正常。发现了c.275G>C(p.Arg92Pro)新突变,扩展了GLIALCAM突变谱,为准确的遗传咨询和产前诊断提供了依据。

Identification in Chinese patients with GLIALCAM mutations of megalencephalic leukoencephalopathy with subcortical cysts and brain pathological study on Glialcam knock-in mouse models

Background Megalencephalic leukoencephalopathy with subcortical cysts(MLC)is a rare neurological degenerative disorder caused by the mutations of MLC1 or GLIALCAM with autosomal recessive or autosomal dominant inheritance and a different prognosis,characterized by macrocephaly,delayed motor and cognitive development,and bilateral abnormal signals in cerebral white matter(WM)with or without cysts on magnetic resonance imaging(MRI).This study aimed to reveal the clinical and genetic features of MLC patients with GLIALCAM mutations and to explore the brain pathological characteristics and prognosis of mouse models with different modes of inheritance.Methods Clinical information and peripheral venous blood were collected from six families.Genetic analysis was performed by Sanger sequencing of GLIALCAM.Glialcam^(Arg92Trp/+)and Glialcam^(Lys68Met/Thr132Asn)mouse models were generated based on mutations from patients(c.274C>T(p.Arg92Trp)(c.203A>T(p.Lys68Met),and c.395C>A(p.Thr132Asn))).Brain pathologies of the mouse models at different time points were analyzed.Results Six patients were clinically diagnosed with MLC.Of the six patients,five(Pt1-Pt5)presented with a heterozygous mutation in GLIALCAM(c.274C>T(p.Arg92Trp)or c.275G>C(p.Arg92Pro))and were diagnosed with MLC2B;the remaining patient(Pt6)with two compound heterozygous mutations in GLIALCAM(c.203A>T(p.Lys68Met)and c.395C>A(p.Thr132Asn))was diagnosed with MLC2A.The mutation c.275C>G(p.Arg92Pro)has not been reported before.Clinical manifestations of the patient with MLC2A(Pt6)progressed with regression,whereas the course of the five MLC2B patients remained stable or improved.The Glialcam^(Arg92Trp/+)and Glialcam^(Lys68Met/Thr132Asn)mouse models showed vacuolization in the anterior commissural WM at 1 month of age and vacuolization in the cerebellar WM at 3 and 6 months,respectively.At 9 months,the vacuolization of the GlialcamiLys68Met/Thr132Asn mouse model was heavier than that of the Glialcam^(Arg92Trp/+)mouse model.Decreased expression of Glialcam in Glialcam^(Arg92Trp/+)and Glialcam^(Lys68Met/Thr132Asn)mice may contribute to the vacuolization.Conclusions Clinical and genetic characterization of patients with MLC and GLIALCAM mutations revealed a novel mutation,expanding the spectrum of GLIALCAM mutations.The first Glialcam mouse model with autosomal recessive inheritance and a new Glialcam mouse model with autosomal dominant inheritance were generated.The two mouse models with different modes of inheritance showed different degrees of brain pathological features,which were consistent with the patients'phenotype and further confirmed the pathogenicity of the corresponding mutations.

胶质细胞病——伴皮层下囊肿的巨脑性脑白质病致病机制研究进展

伴皮层下囊肿的巨脑性脑白质病(MLC)是MLC1或GlialCAM突变导致的星形胶质细胞功能障碍的中枢神经系统髓鞘变性疾病,以星形胶质细胞肿胀与髓鞘囊泡形成为特征性病理改变。MLC/GlialCAM与ClC-2共定位于星形胶质细胞终足处,既往研究发现MLC1/GlialCAM突变后影响ClC-2通道的电容传导性,导致星形胶质细胞的水离子稳态失衡参与MLC的发病,但在GlialCAM纯合敲除的小鼠中,通过与选择性开放Clc-2通道的转基因小鼠杂交并不能纠正小鼠表型,提示有其他因素共同参与了MLC的发生发展。最近研究表明,突变后的MLC1通过促进Connexin43的内化,减少其在细胞膜处形成缝隙连接,影响细胞间通讯效率,从而导致水肿形成和髓鞘囊泡形成,进一步导致MLC的发生。这些研究提示,少突胶质细胞、星形胶质细胞及缝隙连接蛋白等构成的胶质细胞合胞体的功能异常是MLC致病机制的研究方向。