Evolutionary Analysis Predicts Sensitive Positions of MMP20 and Validates Newly- and Previously-Identified MMP20 Mutations Causing Amelogenesis Imperfecta

Abstract

Amelogenesis imperfecta (AI) designates a group of genetic diseases characterized by a large range of enamel disorders causing important social and health problems. These defects can result from mutations in enamel matrix proteins or protease encoding genes. A range of mutations in the enamel cleavage enzyme matrix metalloproteinase-20 gene (MMP20) produce enamel defects of varying severity. To address how various alterations produce a range of AI phenotypes, we performed a targeted analysis to find MMP20 mutations in French patients diagnosed with non-syndromic AI. Genomic DNA was isolated from saliva and MMP20 exons and exon-intron boundaries sequenced. We identified several homozygous or heterozygous mutations, putatively involved in the AI phenotypes. To validate missense mutations and predict sensitive positions in the MMP20 sequence, we evolutionarily compared 75 sequences extracted from the public databases using the Datamonkey webserver. These sequences were representative of mammalian lineages, covering more than 150 million years of evolution. This analysis allowed us to find 324 sensitive positions (out of the 483 MMP20 residues), pinpoint functionally important domains, and build an evolutionary chart of important conserved MMP20 regions. This is an efficient tool to identify new- and previously-identified mutations. We thus identified six functional MMP20 mutations in unrelated families, finding two novel mutated sites. The genotypes and phenotypes of these six mutations are described and compared. To date, 13 MMP20 mutations causing AI have been reported, making these genotypes and associated hypomature enamel phenotypes the most frequent in AI.

Spectrum of pathogenic variants and founder effects in amelogenesis imperfecta associated with MMP20

“…The variant identified in Families 1-3, (c.954-2A>T), has been reported previously (Gasse et al, 2017;J. W. Kim et al, 2005;Prasad et al, 2015;Wright et al, 2011), but it has not been possible to confirm the effect on splicing experimentally since MMP20 is not expressed in blood.…”

“…Families 2 and 3 are Caucasian European families from the United Kingdom. The c.954-2A>T variant has been reported previously in at least six families from France (Gasse et al, 2017;Prasad et al, 2015) and one from the United States (J. W. Kim et al, 2005). Ethnicity is given as Caucasian by Prasad and co-workers but is not given in the remaining reports.…”

MMP20 Overexpression Disrupts Molar Ameloblast Polarity and Migration

“…Therefore, MMP20 is essential for proper enamel development. Twelve different human MMP20 mutations are currently known to cause autosomal recessive amelogenesis imperfecta (Kim et al 2005; Ozdemir et al 2005; Papagerakis et al 2008; Lee et al 2010; Wright et al 2011; Gasse et al 2013; Wang et al 2013; Seymen et al 2015; Gasse et al 2017; Kim et al 2017). MMP20 cleaves enamel matrix proteins during early enamel development (Ryu et al 1999; Nagano et al 2009), and recent literature suggests that MMP20 may also facilitate ameloblast movement by cleaving cadherin extracellular domains (Bartlett and Smith 2013; Guan and Bartlett 2013).…”

Spectrum of pathogenic variants and multiple founder effects in amelogenesis imperfecta associated withMMP20

“…The variant identified in Families 1-3, (c.954-2A>T), has been reported previously (Gasse et al, 2017;J. W. Kim et al, 2005;Prasad et al, 2015;J.…”

“…Families 2 and 3 are Caucasian European families from the UK. The c.954-2A>T variant has been reported previously in at least six families from France (Gasse et al, 2017;Prasad et al, 2015) and one from the USA (J. W. Kim et al, 2005). Ethnicity is given as Caucasian by Prassad and co-workers but is not given in the remaining reports.…”