Enamel proteins and proteases in Mmp20 and Klk4 null and double‐null mice

Abstract

Matrix metalloproteinase 20 (MMP20) and kallikrein-related peptidase 4 (KLK4) are thought to be necessary to clear proteins from the enamel matrix of developing teeth. We characterized Mmp20 and Klk4 null mice to better understand their roles in matrix degradation and removal. Histological examination showed retained organic matrix in Mmp20, Klk4, and Mmp20/Klk4 double-null mouse enamel matrix, but not in the wild-type. X-gal histostaining of Mmp20 null mice heterozygous for the Klk4 knockout/lacZ knockin showed that Klk4 is expressed normally in the Mmp20 null background. This finding was corroborated by zymogram and western blotting, which discovered a 40-kDa protease induced in the maturation stage of Mmp20 null mice. Proteins were extracted from secretory-stage or maturation-stage maxillary first molars from wild-type, Mmp20 null, Klk4 null, and Mmp20/Klk4 double-null mice and were analyzed by SDS-PAGE and western blotting. Only intact amelogenins and ameloblastin were observed in secretory-stage enamel of Mmp20 null mice, whereas the secretory-stage matrix from Klk4 null mice was identical to the matrix from wild-type mice. More residual matrix was observed in the double-null mice compared with either of the single-null mice. These results support the importance of MMP20 during the secretory stage and of KLK4 during the maturation stage and show there is only limited functional redundancy for these enzymes.

Combined effect of amoxicillin and sodium fluoride on the structure of developing mouse enamel in vitro

“…The present result, possibly reflecting low MMP20 expression would be in line with the result of Bourd-Boittin and coworkers 26 obtained using maristat-treated tooth germs and also with the observations in Mmp20 null and Mmp20 + Klk4 double null mice. 22,28,30 In the present study, amoxicillin treatment reduced the extent of enamel measured as the vertical enamel height/ crown height ratio from the whole tooth photographs, indicating delayed commencement of secretion by ameloblasts. Earlier we reported that amoxicillin increased the thickness of developing enamel.…”

Critical roles for WDR72 in calcium transport and matrix protein removal during enamel maturation

“…2011). In brief, D14 first molars were harvested and, for 4 molars collected from one mouse, incubated in 1 mL of 0.17 N HCl/0.95% formic acid for 2 h at 4°C.…”

Construction of enamel and its resistance to pathological factors. A literature review

“…MMP-20 lokalizuje się na chromosomie 11 i jest to gen autosomalny recesywny. Podczas badań na zębach myszy wykazano, że zarówno delecja genu AMELX, jak i MMP-20 powodowała powstawanie szkliwa o chropowatej powierzchni bez struktury pryzmatycznej (15).…”