Amelogenesis imperfecta (AI) is a group of enamel development disorders that alter the structure and chemical composition of the tissue. There is great variability in the clinical presentation; according to Witkop, AI can be categorized into 14 subtypes, which makes its diagnosis extremely complex.

Objective. The purpose of this study was to conduct a multidisciplinary analysis of a specific type of tooth enamel disturbance (amelogenesis imperfecta) affecting two Chilean families to obtain a precise diagnosis and to investigate possible underlying mutations. Materials and methods. Two non-related families affected with amelogenesis imperfecta were evaluated with clinical, radiographic and histopathological methods. Furthermore, pedigrees of both families were constructed and the presence of eight mutations in the enamelin gene (ENAM) and three mutations in the enamelysin gene (MMP-20) were investigated by PCR and direct sequencing. Results. In the two affected patients, the dental malformation presented as soft and easily disintegrated enamel and exposed dark dentin. Neither of the affected individuals presented with a dental and skeletal open bite. Histologically, a high level of an organic matrix with prismatic organization was found. Genetic analysis indicated that the condition is autosomal recessive in one family and either autosomal recessive or due to a new mutation in the other family. Molecular mutational analysis revealed that none of the eight mutations previously described in the ENAM gene or the three mutations in the MMP-20 gene were present in the probands. Conclusion . A multidisciplinary analysis allowed for a diagnosis of hypocalcified amelogenesis imperfecta, Witkop type III, which was unrelated to previously described mutations in the ENAM or MMP-20 genes.

The Phaffia rhodozyma UCD 67-385 genome harbors a 7873 bp cluster containing DDGS, OMT, and ATPG, encoding 2-desmethy-4-deoxygadusol synthase, O-methyl transferase, and ATP-grasp ligase, respectively, of the mycosporine glutaminol (MG) biosynthesis pathway. Homozygous deletion mutants of the entire cluster, single-gene mutants, and the Δddgs^−/−;Δomt^−/− and Δomt^−/−;Δatpg^−/− double-gene mutants did not produce mycosporines. However, Δatpg^−/− accumulated the intermediate 4-deoxygadusol. Heterologous expression of the DDGS and OMT or DDGS, OMT, and ATPG cDNAs in Saccharomyces cerevisiae led to 4-deoxygadusol or MG production, respectively. Genetic integration of the complete cluster into the genome of the non-mycosporine-producing CBS 6938 wild-type strain resulted in a transgenic strain (CBS 6938_MYC) that produced MG and mycosporine glutaminol glucoside. These results indicate the function of DDGS, OMT, and ATPG in the mycosporine biosynthesis pathway. The transcription factor gene mutants Δmig1^−/−, Δcyc8^−/−, and Δopi1^−/− showed upregulation, Δrox1^−/− and Δskn7^−/− showed downregulation, and Δtup6^−/− and Δyap6^−/− showed no effect on mycosporinogenesis in glucose-containing medium. Finally, comparative analysis of the cluster sequences in several P. rhodozyma strains and the four newly described species of the genus showed the phylogenetic relationship of the P. rhodozyma strains and their differentiation from the other species of the genus Phaffia.

Amelogenesis Imperfecta (AI) is a group of conditions where there is an abnormal formation of enamel in terms of quantity, structure and composition. AI is clinically and genetically heterogeneous, there are sex linked and autosomal versions, dominant and/or recessive, with phenotypes of hypoplastic, hypocalcified or hypomature enamel. Only recently, through clinical, genetic and molecular studies of affected families, phenotypic-genotypic correlations are being established in this group of anomalies. To carry out a genetic, clinical and molecular analysis of a Chilean family affected with an enamel malformation, which probably would correspond to Amelogenesis Imperfecta Dominant Autosomal (AIDA), of hypoplastic type, resulting from g.6395G>A mutation in the enamelin gene. A genealogical pattern was created for five generations. Five members of this family group were clinically examined, and four of them had a molecular analysis that consisted of the detection of a mutation in the enamelin gene using PCR. In this family, the enamel malformation presents a dominant autosomal pattern of inheritance. The clinical examination of the group allowed a diagnosis of Amelogenesis Imperfecta, of the hypoplastic local type. However, the molecular analysis revealed that the members analyzed did not exhibit the g.6395G>A mutation reported for the enamelin gene (ENAM). The enamel phenotype in this family could be explained by the presence of one of four other mutations recently described in this or another gene, thereby supporting the findings of allelic heterogeneity reported in the literature.