Epileptic phenotype spectrum of SLC6A1 gene mutations and their genotype-phenotype correlation
10.3760/cma.j.cn115354-20240909-00552
- VernacularTitle:SLC6A1基因突变致癫痫表型谱及其基因型-临床表型关系研究
- Author:
Jie WANG
1
;
Xin XIE
;
Junhui ZHU
;
Jingjing JI
;
Chuanfang CHENG
Author Information
1. 广州医科大学附属第二医院广州医科大学神经科学研究所，广州 510260
- Keywords:
SLC6A1 gene;
Gene mutation;
Epileptic phenotype spectrum;
Genotype-phenotype correlation
- From:
Chinese Journal of Neuromedicine
2024;23(11):1129-1139
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To explore the epileptic phenotype spectrum of SLC6A1 gene mutations and their genotype-phenotype correlation. Methods:Four hundred patients with epilepsy of unknown etiology admitted to Epilepsy Center, Department of Neurology, Second Affiliated Hospital of Guangzhou Medical University from July 2019 to July 2024 were enrolled to screen the SLC6A1 gene mutations; the clinical characteristics, mutation pathogenicity, and changes of hydrogen bond between amino acids, stability and amino acid hydrophobicity of SLC6A1 gene encoded proteins caused by missense mutations in patients with SLC6A1 gene mutations were analyzed. At the same time, a comprehensive search was conducted in PubMed, HGMD and CNKI databases to collect the publicly reported SLC6A1 gene mutations related to epilepsy up to September 8, 2024; differences in proportion of missense mutations between the two most common and featured epileptic phenotypes and proportion of missense mutations in loops of SLC6A1 gene coding proteins were analyzed. Results:Five patients carried SLC6A1 gene mutations in 400 patients with epilepsy of unknown etiology: 2 had de novo heterozygous canonical splice site mutations (c.850-1G>A and c.1324-1G>A), with phenotypes as partial epilepsy combined with severe development delay and childhood absence epilepsy combined with mild developmental delay; 2 had de novo heterozygous missense mutations (c.187G>A/p.Gly63Ser and c.1081C>A/p.Pro361Thr), with phenotypes as partial epilepsy combined with mild development delay and generalized epilepsy combined with severe development delay; and one had heterozygous missense mutation of unknown origin (c.700G>A/p.Gly234Ser), with phenotype as Lennox-Gastaut syndrome. Four de novo mutations were evaluated as having pathogenic or likely pathogenic features, and one mutation of unknown origin was evaluated as of uncertain significance. In addition, 3 missense mutations caused significant changes in number or bonding form of hydrogen bonds between amino acids of the encoded proteins, with obviously decreased stability and hydrophobicity of the encoded proteins. (2) Results of literature analysis showed that 84 SLC6A1 mutations have been reported to be associated with epilepsy; combined with the genetic results in this study, a total of 89 SLC6A1 mutations were identified, including 53 missense mutations, 33 nonsense mutations, and 3 in-frame/in-del mutations; 7 epilepsy phenotypes were involved, including 38 patients with myoclonic atonic epilepsy (MAE), 16 with epilepsy, 12 with epileptic encephalopathy, 8 with childhood absence epilepsy, 6 with childhood-onset epilepsy, 6 with generalized epilepsy, and 3 with focal epilepsy. No significant difference in proportion of missense mutations was noted between MAE and epileptic encephalopathy patients ( P>0.05); however, the proportion of missense mutations in loops of the epileptic encephalopathy patients was significantly higher than that of the MAE patients ( P<0.05). Conclusion:SLC6A1 gene mutations can cause complex and diverse epilepsy phenotype spectrum, and most patients are accompanied by developmental delay; subregional effect of the encoded protein molecules may be a potential mechanism for different clinical phenotypes between MAE and epileptic encephalopathy caused by SLC6A1 gene mutations.
