Screening and functional analysis of mutations in NEUROD1 gene in pedigrees of maturity-onset diabetes of the young
ZHANG Juan,1, GE Xiaoxu2,3, ZHANG Rong2, JIANG Fusong2, JIANG Yanyan2, LI Ming2, LI Tiantian2, LIU Chanwei2, CHEN Yating2, LIU Limei,2
1.Department of Morphology, School of Medicine, Huanghuai University, Zhumadian 463000, China
2.Department of Endocrinology and Metabolism, Shanghai Sixth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Diabetes Institute, Shanghai 200233, China
3.Department of Endocrinology and Metabolism, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200336, China
目的·筛查青少年的成人起病型糖尿病（maturity-onset diabetes of the young，MODY）家系中NEUROD1基因突变，分析突变与中国人MODY6发病的相关性及其潜在的致病机制。方法·采用PCR-直接测序法对96例GCK/MODY2、HNF1A/MODY3、HNF1B/MODY5突变阴性的中国MODY先证者进行NEUROD1突变筛查，同时比较96例MODY先证者与100例非糖尿病对照者NEUROD1基因变异的基因型频率。采用从头建模法构建NEUROD1蛋白野生型和突变体的3D结构，采用双荧光素酶报告基因系统检测野生型和突变体蛋白对胰岛素基因转录活性的影响。结果·在一个MODY家系中发现NEUROD1基因杂合错义突变Glu59Gln（NM_002500.5，c.175G>C）。3D结构分析发现，该突变将野生型中带负电荷的Glu59转化为突变中不带电荷的Gln59，导致两个盐桥键Glu59-Arg54和Glu59-Lys88缺失，并形成一个新的氢键Gln59- Arg54。与野生型相比，Glu59Gln突变体的胰岛素基因转录活性下降36.3％（P<0.05）。与非糖尿病对照相比，96例MODY先证者中Ala45Thr（G-A）变异的AA+GA基因型频率显著升高（P=0.002）。结论·Glu59Gln突变改变了NEUROD1蛋白N端的分子构象，导致其胰岛素基因转录活性显著下降，是该家系突变携带者胰岛素分泌缺陷的原因。Ala45Thr变异与MODY6先证者糖尿病发病年龄的提前有关。
Objective ·To screen the mutations of NEUROD1 gene in families of maturity-onset diabetes of the young (MODY), and investigate the correlation between the mutation and MODY6 and its potential pathogenesis in Chinese. Methods ·PCR-direct sequencing was used for screening NEUROD1 mutations from 96 MODY probands who were negative for mutations in the GCK/MODY2, HNF1A/MODY3 and HNF1B/MODY5 genes, and the genotypic frequency of NEUROD1 variations were compared between the 96 MODY probands and 100 non-diabetic control subjects. A de novo modeling method was used to predict the three-dimensional (3D) structures of wild type (WT) and mutated NEUROD1 proteins. Transcriptional activities of both WT and mutant of NEUROD1 on insulin gene were detected by using dual luciferase reporter gene system. Results ·Glu59Gln (NM_002500.5, c.175G>C), a heterozygous missense mutation in the NEUROD1 gene, was identified in a MODY pedigree. 3D structural analysis showed that the mutation transformed the negatively charged Glu59 of WT into uncharged mutation Gln59, leading to the loss of Glu59-Arg54 and Glu59-Lys88, two salt bridge bonds, and the formation of Gln59-Arg54, one new hydrogen bond. Transcriptional activity of Glu59Gln mutant for insulin gene was reduced by 36.3% when compared with that of WT (P<0.05). A common variation Ala45Thr (G-A) was identified, and AA+GA genotypic frequency of the variation was significantly elevated in the 96 MODY probands in comparison to non-diabetic control subjects (P=0.002). Conclusion ·Glu59Gln mutation alters the N-terminal molecular conformation of NEUROD1 protein, resulting in decreased transcriptional activity of insulin gene, which is the cause of the defective insulin secretion in mutation carriers of the MODY6 pedigree. The Ala45Thr variation is associated with earlier age of onset of diabetes in MODY6 probands.
Keywords：maturity-onset diabetes of the young (MODY)
;
NEUROD1 gene
;
MODY6
;
Glu59Gln mutation
;
functional analysis
ZHANG Juan, GE Xiaoxu, ZHANG Rong, JIANG Fusong, JIANG Yanyan, LI Ming, LI Tiantian, LIU Chanwei, CHEN Yating, LIU Limei. Screening and functional analysis of mutations in NEUROD1 gene in pedigrees of maturity-onset diabetes of the young. Journal of Shanghai Jiao Tong University (Medical Science)[J], 2023, 43(10): 1255-1261 doi:10.3969/j.issn.1674-8115.2023.10.005
NEUROD1蛋白又名BETA2，是一种碱性螺旋-环-螺旋（basic helix-loop-helix，bHLH）转录因子，不仅调节内分泌胰腺发育，而且与细胞中广泛存在的bHLH蛋白E47结合形成异源二聚体，作用于胰岛素启动子，激活胰岛素基因表达［1］。在胰岛素基因转录中起主导作用的NEUROD1能够与转录因子PDX1和MafA相互作用，协同激活胰岛β细胞中的胰岛素基因［2］。除胰岛素基因外，NEUROD1还激活青少年的成人起病型糖尿病（maturity-onset diabetes of the young，MODY）其他相关基因，如ABCC8/MODY12、GCK/MODY2和转录因子基因PAX6，从而间接调节胰岛素基因的转录和表达［3］。
Note： A. Schematic organization of NEUROD1 protein. The numbers indicate the amino acids bordering the functional domains. Solid and dashed arrows indicate the identified mutation Glu59Gln and variation Ala45Thr in NEUROD1 gene, respectively. B. Alignment of specific regions of NEUROD1 from different mammals using Clustal O. C. DNA sequences of two genotypes of WT (Glu59Glu) and mutant (Glu59Gln) in NEUROD1.
Fig 1
Identification of Glu59Gln mutation in NEUROD1 gene
Note： A/B. The location of wild type Glu59(A) and mutant Gln59(B) on the global landscape of NEUROD1 protein. C. Interaction of Glu59 with surrounding residues. The side chains of Glu59 formed strong salt bridge bonds with Arg54 and Lys88, and the main chains of Glu59 formed hydrogen bonds with Gly56 and Asp61, respectively. D. Interaction of Gln59 with surrounding amino acids. In the Glu59Gln mutation, the salt-bridge bonds of the side chains of Glu59 were disrupted, while the mutated Gln59 formed a new hydrogen bond with Arg54. Blue dotted lines represent salt bridge bonds formed between amino acids, while green dotted lines represent hydrogen bonds.
Fig 2
3D structural models of wild type and Glu59Gln mutant of NEUROD1 protein
Note：A. Relative luciferase activities of the human insulin promoter luciferase reporter gene stimulated by mNeuroD1-WT and mNeuroD1-Glu59Gln in MIN6 cells. B. Expression of mNeuroD1-WT-Flag and mNeuroD1-Glu59Gln-Flag by Western blotting assay in MIN6 cells. ①P=0.000,compared with NC; ②P=0.024, compared with mNeuroD1-WT. NC—pcDNA3.3.
Fig 3
Transcriptional activities of wild type and mutant of NeuroD1 protein
LIU Limei designed the study and finalized the draft. ZHANG Juan and GE Xiaoxu wrote the paper. The data was collected and analyzed by ZHANG Rong, JIANG Fusong, JIANG Yanyan, LI Ming, LI Tiantian, LIU Chanwei and CHEN Yating. All the authors have read the last version of paper and consented for submission.
利益冲突声明
所有作者声明不存在利益冲突。
All authors disclose no relevant conflict of interests.
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... NEUROD1蛋白又名BETA2，是一种碱性螺旋-环-螺旋（basic helix-loop-helix，bHLH）转录因子，不仅调节内分泌胰腺发育，而且与细胞中广泛存在的bHLH蛋白E47结合形成异源二聚体，作用于胰岛素启动子，激活胰岛素基因表达［1］.在胰岛素基因转录中起主导作用的NEUROD1能够与转录因子PDX1和MafA相互作用，协同激活胰岛β细胞中的胰岛素基因［2］.除胰岛素基因外，NEUROD1还激活青少年的成人起病型糖尿病（maturity-onset diabetes of the young，MODY）其他相关基因，如ABCC8/MODY12、GCK/MODY2和转录因子基因PAX6，从而间接调节胰岛素基因的转录和表达［3］. ...
... NEUROD1蛋白又名BETA2，是一种碱性螺旋-环-螺旋（basic helix-loop-helix，bHLH）转录因子，不仅调节内分泌胰腺发育，而且与细胞中广泛存在的bHLH蛋白E47结合形成异源二聚体，作用于胰岛素启动子，激活胰岛素基因表达［1］.在胰岛素基因转录中起主导作用的NEUROD1能够与转录因子PDX1和MafA相互作用，协同激活胰岛β细胞中的胰岛素基因［2］.除胰岛素基因外，NEUROD1还激活青少年的成人起病型糖尿病（maturity-onset diabetes of the young，MODY）其他相关基因，如ABCC8/MODY12、GCK/MODY2和转录因子基因PAX6，从而间接调节胰岛素基因的转录和表达［3］. ...
3
... NEUROD1蛋白又名BETA2，是一种碱性螺旋-环-螺旋（basic helix-loop-helix，bHLH）转录因子，不仅调节内分泌胰腺发育，而且与细胞中广泛存在的bHLH蛋白E47结合形成异源二聚体，作用于胰岛素启动子，激活胰岛素基因表达［1］.在胰岛素基因转录中起主导作用的NEUROD1能够与转录因子PDX1和MafA相互作用，协同激活胰岛β细胞中的胰岛素基因［2］.除胰岛素基因外，NEUROD1还激活青少年的成人起病型糖尿病（maturity-onset diabetes of the young，MODY）其他相关基因，如ABCC8/MODY12、GCK/MODY2和转录因子基因PAX6，从而间接调节胰岛素基因的转录和表达［3］. ...
