Basic Study
Copyright ©The Author(s) 2024. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Diabetes. Feb 15, 2024; 15(2): 275-286
Published online Feb 15, 2024. doi: 10.4239/wjd.v15.i2.275
Assessment of pathogenicity and functional characterization of APPL1 gene mutations in diabetic patients
Ping Shi, Yang Tian, Feng Xu, Lu-Na Liu, Wan-Hong Wu, Ying-Zhou Shi, An-Qi Dai, Hang-Yu Fang, Kun-Xia Li, Chao Xu
Ping Shi, Yang Tian, Feng Xu, Lu-Na Liu, Wan-Hong Wu, Ying-Zhou Shi, An-Qi Dai, Hang-Yu Fang, Chao Xu, Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan 250021, Shandong Province, China
Kun-Xia Li, Department of Pediatric, Yantai Yuhuangding Hospital Affiliated to Qingdao University, Yantai 264099, Shandong Province, China
Co-corresponding authors: Kun-Xia Li and Chao Xu.
Author contributions: Li KX and Xu C are the co-corresponding authors of this manuscript; Xu C acted as a guarantor for the research design and manuscript revision; Li KX designed the theme of the article; Shi P carried out the experiments and wrote the manuscript; Tian Y contributed to the experiment implementation and data collection; Xu F edited and reviewed the content of the manuscript; Liu LN and Wu WH contributed to the experiment implementation and data analysis; Shi YZ, Dai AQ, and Fang HY performed bioinformation analysis and graph drawing; and all authors read and approved the final manuscript.
Supported by the National Natural Science Foundation, No. 81974124; and Taishan Scholar Project, No. tsqn20161071.
Institutional review board statement: The study was reviewed and approved by the Ethics Committee of Shandong Provincial Hospital.
Conflict-of-interest statement: All the authors report having no relevant conflicts of interest for this article.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Chao Xu, MD, Doctor, Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, No. 324 Jingwu Weiqi Road, Jinan 250021, Shandong Province, China. doctorxuchao@163.com
Received: October 2, 2023
Peer-review started: October 2, 2023
First decision: November 9, 2023
Revised: November 22, 2023
Accepted: January 9, 2024
Article in press: January 9, 2024
Published online: February 15, 2024
ARTICLE HIGHLIGHTS
Research background

Mutations in the adaptor protein, phosphotyrosine interacting with PH domain and leucine zipper 1 (APPL1) gene have been associated with the development of maturity-onset diabetes of the young type 14 (MODY14), a rare form of monogenic diabetes. So far, only two mutations [c.1655T>A (p.Leu552*) and c.281G>A p.(Asp94Asn)] have been found to be related to this disease. Due to the limited knowledge of MODY14, it is necessary to identify more cases and conduct a comprehensive study of MODY14 and APPL1 mutations. In this study, we discovered five new APPL1 gene mutations by whole exome sequencing (WES) and bioinformatics analysis, of which two were confirmed to be pathogenic mutations by in vitro functional assays. These mutations were all located in the phosphotyrosine binding (PTB) domain of APPL1, which has a significant impact on insulin sensitivity.

Research motivation

This study aimed to identify the pathogenicity and functional role of APPL1 gene mutations in diabetes. It mainly identified and evaluated the pathogenicity of APPL1 gene mutations and explored the effects of these mutations on APPL1 protein expression and insulin signaling pathway. This will provide potential targets for the diagnosis and treatment of MODY14 and will provide new clues for the interaction mechanism of the APPL1 protein and insulin receptor.

Research objectives

The main objective of this study was to evaluate the pathogenicity of APPL1 gene mutations in diabetic patient and to characterize the functional role of APPL1 domains. By WES and bioinformatics analysis, five novel APPL1 gene mutations were identified, among which c.1894G>T (at Asp632Tyr) and c.1595G>A (at Arg532Gln) were confirmed as pathogenic mutations by in vitro functional experiments.

Research methods

This study used WES to sequence all the exons in the genome that encode proteins, thus discovering variants associated with diseases. Then, bioinformatics analysis was used to align and predict the sequencing results, thus evaluating the pathogenicity and conservation of the variants. The pathogenicity was further verified by in vitro functional experiments.

Research results

Our study identified five novel APPL1 gene mutations, among which c.1894G>T (at Asp632Tyr) and c.1595G>A (at Arg532Gln) were confirmed as pathogenic mutations by in vitro functional experiments. Both mutations are located in the PTB domain of APPL1, which has an important impact on insulin sensitivity. The results showed that the mutations can reduce the expression level of APPL1 protein, thus affecting the activation of the insulin signaling pathway and the regulation of glucose metabolism.

Research conclusions

APPL1 gene mutations c.1894G>T (at Asp632Tyr) and c.1595G>A (at Arg532Gln) are pathogenic in diabetes, and these mutations are located in the PTB domain of APPL1, which has an important impact on insulin sensitivity.

Research perspectives

In the future, the structure and function of APPL1 protein can be further studied, especially the mechanism of action of the PTB domain and the binding mode and regulatory effect of APPL1 protein with the insulin receptor. In addition, the effect of APPL1 gene mutations on the clinical manifestations and treatment response of diabetic patients can be verified. More effective methods and criteria for the diagnosis and treatment of MODY14 can be provided.