1. AMBN mutations causing hypoplastic amelogenesis imperfecta and Ambn knockout-NLS-lacZ knockin mice exhibiting failed amelogenesis and Ambn tissue-specificity
- Author
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Liang, Tian, Hu, Yuanyuan, Smith, Charles E, Richardson, Amelia S, Zhang, Hong, Yang, Jie, Lin, Brent, Wang, Shih-Kai, Kim, Jung-Wook, Chun, Yong-Hee, Simmer, James P, and Hu, Jan C-C
- Subjects
Amelogenesis Imperfecta ,Clinical Sciences ,matrix proteins ,Amelx ,amelin ,Transgenic ,Mice ,Medicinal and Biomolecular Chemistry ,ameloblastin ,Rare Diseases ,Dental Enamel Proteins ,Ameloblasts ,Genetics ,Animals ,Humans ,2.1 Biological and endogenous factors ,mineralization ,Ambn ,Gene Knock-In Techniques ,Dental/Oral and Craniofacial Disease ,Aetiology ,dental enamel formation ,missense mutation ,sheath protein ,amelogenin ,Organ Specificity ,Dentin ,Mutation ,sheathlin ,Ambn -/- Amelx - Abstract
BackgroundAmeloblastin (AMBN) is a secreted matrix protein that is critical for the formation of dental enamel and is enamel-specific with respect to its essential functions. Biallelic AMBN defects cause non-syndromic autosomal recessive amelogenesis imperfecta. Homozygous Ambn mutant mice expressing an internally truncated AMBN protein deposit only a soft mineral crust on the surface of dentin.MethodsWe characterized a family with hypoplastic amelogenesis imperfecta caused by AMBN compound heterozygous mutations (c.1061T>C; p.Leu354Pro/ c.1340C>T; p.Pro447Leu). We generated and characterized Ambn knockout/NLS-lacZ (AmbnlacZ/lacZ ) knockin mice.ResultsNo AMBN protein was detected using immunohistochemistry in null mice. ß-galactosidase activity was specific for ameloblasts in incisors and molars, and islands of cells along developing molar roots. AmbnlacZ/lacZ 7-week incisors and unerupted (D14) first molars showed extreme enamel surface roughness. No abnormalities were observed in dentin mineralization or in nondental tissues. Ameloblasts in the AmbnlacZ/lacZ mice were unable to initiate appositional growth and started to degenerate and deposit ectopic mineral. No layer of initial enamel ribbons formed in the AmbnlacZ/lacZ mice, but pockets of amelogenin accumulated on the dentin surface along the ameloblast distal membrane and within the enamel organ epithelia (EOE). NLS-lacZ signal was positive in the epididymis and nasal epithelium, but negative in ovary, oviduct, uterus, prostate, seminal vesicles, testis, submandibular salivary gland, kidney, liver, bladder, and bone, even after 15hr of incubation with X-gal.ConclusionsAmeloblastin is critical for the initiation of enamel ribbon formation, and its absence results in pathological mineralization within the enamel organ epithelia.
- Published
- 2019