The use of animal models to explore amelogenin variants in amelogenesis imperfecta
CELLS TISSUES ORGANS
Authors: Gibson, CW; Kulkarni, AB; Wright, JT
Abstract
Amelogenin proteins are secreted by ameloblast cells during tooth development. Because of extensive alternative splicing of the amelogenin primary RNA transcript, and because systematic proteolysis results in many additional peptides during enamel maturation, it has been difficult to assign function to individual amelogenins. Targeted deletions and transgenic mice have been generated in order to better understand amelogenin protein function in vivo. From these murine models, we have determined that amelogenins are responsible for normal enamel thickness and structure, but not for initiation of enamel mineral formation at the dentin-enamel junction. Although it is now clear that the amelogenin (AmelX) gene exists in a nested orientation and that AmelX is expressed at a low level in various developing tissues, the significance of these findings is incompletely understood. Future studies are expected to answer remaining questions concerning structure/function relationships among these 'enamel proteins'. Copyright (c) 2005 S. Karger AG, Basel.
Novel WDR72 Mutation and Cytoplasmic Localization
JOURNAL OF DENTAL RESEARCH
Authors: Lee, S. -K.; Seymen, F.; Lee, K. -E.; Kang, H. -Y.; Yildirim, M.; Tuna, E. Bahar; Gencay, K.; Hwang, Y. -H.; Nam, K. H.; De La Garza, R. J.; Hu, J. C. -C.; Simmer, J. P.; Kim, J. -W.
Abstract
The proven candidate genes for amelogenesis imperfecta (AI) are AMELX, ENAM, MMP20, KLK4, FAM83H, and WDR72. We performed mutation analyses on seven families with hypo-maturation AI. A novel WDR72 dinucleotide deletion mutation (g.57,426_57,427delAT; c.1467_1468delAT; p.V491fsX497) was identified in both alleles of probands from Mexico and Turkey. Haplotype analyses showed that the mutations arose independently in the two families. The disease perfectly segregated with the genotype. Only persons with both copies of the mutant allele were affected. Their hypomineralized enamel suffered attrition and orange-brown staining following eruption. Expression of WDR72 fused to green fluorescent protein showed a cytoplasmic localization exclusively and was absent from the nucleus. We conclude that WDR72 is a cytoplasmic protein that is critical for dental enamel formation.