Amelogenesis imperfecta caused by N-terminal enamelin point mutations in mice and men is driven by endoplasmic reticulum stress.
'Amelogenesis imperfecta' (AI) describes a group of inherited diseases of dental enamel that have major clinical impact. Here, we identify the aetiology driving AI in mice carrying a p.S55I mutation in enamelin; one of the most commonly mutated proteins underlying AI in humans. Our data indicate that the mutation inhibits the ameloblast secretory pathway leading to ER stress and an activated unfolded protein response (UPR). Initially, with the support of the UPR acting in pro-survival mode, Enamp.S55I heterozygous mice secreted structurally normal enamel. However, enamel secreted thereafter was structurally abnormal; presumably due to the UPR modulating ameloblast behaviour and function in an attempt to relieve ER stress. Homozygous mutant mice failed to produce enamel. We also identified a novel heterozygous ENAMp.L31R mutation causing AI in humans. We hypothesize that ER stress is the aetiological factor in this case of human AI as it shared the characteristic phenotype described above for the Enamp.S55I mouse. We previously demonstrated that AI in mice carrying the Amelxp.Y64H mutation is a proteinopathy. The current data indicate that AI in Enamp.S55I mice is also a proteinopathy, and based on comparative phenotypic analysis, we suggest that human AI resulting from the ENAMp.L31R mutation is another proteinopathic disease. Identifying a common aetiology for AI resulting from mutations in two different genes opens the way for developing pharmaceutical interventions designed to relieve ER stress or modulate the UPR during enamel development to ameliorate the clinical phenotype.
Department of Oral Biology, School of Dentistry, Wellcome Trust Brenner Building University Of Leeds, St James's University Hospital, Leeds LS9 7TF, UK.
Steven J
SJ
Brookes
Faculty of Biology, Medicine & Health, Manchester Academic Health Sciences Centre, University of Manchester, Michael Smith Building, Manchester M13 9PT, UK.
Martin J
MJ
Barron
Department of Oral Medicine, School of Dentistry, University of Leeds, Leeds, UK.
Claire E L
CEL
Smith
Department of Oral Medicine, School of Dentistry, University of Leeds, Leeds, UK.
James A
JA
Poulter
Leeds Institute of Biomedical and Clinical Sciences, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK.
Alan J
AJ
Mighell
Department of Oral Medicine, School of Dentistry, University of Leeds, Leeds, UK.
Chris F
CF
Inglehearn
Birmingham Dental Hospital and School of Dentistry, Birmingham B5 7EG, UK.
Catriona J
CJ
Brown
Unit of Oral Health and Development, School of Clinical Dentistry, University of Sheffield, Sheffield, UK.
Helen
H
Rodd
Department of Oral Biology, School of Dentistry, Wellcome Trust Brenner Building University Of Leeds, St James's University Hospital, Leeds LS9 7TF, UK.
Jennifer
J
Kirkham
Faculty of Biology, Medicine & Health, Manchester Academic Health Sciences Centre, University of Manchester, Michael Smith Building, Manchester M13 9PT, UK.
Michael J
MJ
Dixon
D000565:Ameloblasts / Q000378:metabolism; D000567:Amelogenesis Imperfecta / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D003743:Dental Enamel / Q000378:metabolism; D003746:Dental Enamel Proteins / Q000235:genetics / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D059865:Endoplasmic Reticulum Stress / Q000235:genetics / Q000502:physiology; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D017354:Point Mutation; D013312:Stress, Physiological; D056811:Unfolded Protein Response
D003746:Dental Enamel Proteins; C038456:tuftelin