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Journal of Peking University (Health Sciences) ›› 2025, Vol. 57 ›› Issue (1): 13-18. doi: 10.19723/j.issn.1671-167X.2025.01.003

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Frameshift mutation in RELT gene causes amelogenesis imperfecta

Zhenwei ZHANG1,2, Xinran XU1, Xuejun GAO1, Yanmei DONG1, Hua TIAN1,3,*()   

  1. 1. Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology & National Center for Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Research Center of Oral Biomaterials and Digital Medical Devices, Beijing 100081, China
    2. Department of Conservative Dentistry and Endodontics 2, Shanghai Stomatological Hospital & School of Stomatology; Shanghai Key Laboratory of Craniomaxillofacial Development and Diseases, Fudan University, Shanghai 200001, China
    3. International Clinical Division, Peking University School and Hospital of Stomatology, Beijing 100081, China
  • Received:2024-09-27 Online:2025-02-18 Published:2025-01-25
  • Contact: Hua TIAN E-mail:hua_tian@bjmu.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(81300839);Peking University Medicine Seed Fund for Interdisciplinary Research(BMU2022MX019);National Multidisciplinary Cooperative Diagnosis and Treatment Capacity Building Project for Major Diseases, Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology(PKUSSNMP-201906)

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Abstract:

Objective: To analyze RELT gene mutation found in a pedigree with clinical features and inheritable pattern consistent with amelogenesis imperfecta (AI) in China, and to study the relationship between its genotype and phenotype. Methods: Clinical and radiological features were recorded for the affected individuals. Peripheral venous blood samples of the patient and family members were collected for further study, and the genomic DNA was extracted to identify the pathogenic gene. Whole exome sequencing (WES) was performed to analyze the possible pathogenic genes, and Sanger sequencing was performed for validation. SIFT and PolyPhen-2 were used to predict and analyze the mutation effect. Comparison of RELT amino acids across different species were performed by using Uniprot website. In addition, the three-dimen-sional structures of the wild type and mutant proteins were predicted by Alphafold 2. Results: The proband exhibited typical hypocalcified AI, with heavy wear, soft enamel, rough and discolored surface, and partial enamel loss, while his parents didn ' t have similar manifestations. WES and Sanger sequencing results indicated that the proband carries a homozygous frameshift mutation in RELT gene, NM_032871.3: c.1169_1170del, and both of his parents were carriers. This mutation was predicted to be pathogenic by SIFT and PolyPhen-2. Up to now, there were 11 mutation sites in RELT gene were reported to be associated with AI, and all of the patients exhibited with hypocalcified AI. Compared with the wild-type RELT protein, the mutant protein p. Pro390fs35 conformation terminated prematurely, affecting the normal function of the protein. Conclusion: Through phenotype analysis, gene sequencing, and functional prediction of a Chinese family with typical amelogenesis imperfecta, this study found that RELT gene frameshift mutation can lead to protein dysfunction in AI patients. Further research will focus on the role and mechanism of RELT in enamel development at the molecular and animal levels, providing molecular biology evidence for the genetic counseling, prenatal diagnosis, and early prevention and treatment of AI.

Key words: Amelogenesis imperfecta, RELT gene, Frameshift mutation, Enamel mineralization

CLC Number: 

  • R781.2

Figure 1

Pedigree tree of the proband and clinical images of the pedigree A, pedigree tree, the black arrow indicates the proband; B-D, intraoral photographs of the proband (Ⅱ-1); E, panoramic photograph of Ⅱ-1; F and G, intraoral photographs of Ⅰ-2."

Figure 2

Sanger sequencing of the pedigree The proband (Ⅱ-1) was homozygous, while his parents (Ⅰ-1 and Ⅰ-2) were heterozygous. Red arrows indicated the mutation site."

Figure 3

Conservation analysis and 3D structure of the RELT protein A, comparison of RELT amino acids across different species, the p.390 was highly conserved; B, 3D structure of wild-type RELT protein predicted by Alphafold 2 software; C, 3D structure of mutant RELT protein predicted by Alphafold 2 software, the red arrow indicates the random coil. WT, wild type; MT, mutant type."

Table 1

Description of the mutations in RELT causing AI according to location and clinical features"

LocationcDNAaClinical featuresReferences
Intron 3c.120+1G>AHypomineralized and rough enamel, with attrition of occlusal surfaces[16]
Intron 3c.120+1G>THypomineralized yellow-brown enamel, with attrition of occlusal surfaces and localized pitted hypoplastic enamel[16]
Intron 3c.121-2A>GRough hypoplastic enamel, attrition of occlusal surfaces with ring of thin enamel covering lateral surfaces of the crown[17]
Exon 4c.164C>THypomineralized, normal enamel thickness, post-eruptive loss[24]
Exon 4 Exon11c.193T>C
c.1260_1263dup		Rough and hypomineralized enamel with pits localized in the middle of crown[16]
Exon 4 Exon 6c.260A>T
c.521T>G		Severe enamel hypoplasia affecting both primary molars and permanent teeth, loss of normal crown morphology[25]b
Exon 10c.1169_1170delRough and hypomineralized enamel, attrition of occlusal surfacesThis study and[17]
Exon 11c.1264C>TRough enamel, normal enamel thickness[24]
Exon 11c.1265G>CSevere generalized enamel attrition[17]
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