Phenotype Image Detail

Image

Caption

Analysis of Lama3^tm1Crt/Lama3^tm1Crt developing incisors. (A) Cross-sections were taken from medial to lateral regions of the head. Cartoon (B) and hematoxylin and eosin stained section (C) show the progression of differentiation occurring in the inner dental epithelium from the base of the tooth (region I) to the tip (region III and VI). Mitotic preameloblasts of the inner dental epithelium present in the base of region I develop into post-mitotic, secretory ameloblasts in region II and produce the enamel layer of the tooth. A single layer of cells, referred to as the stratum intermedium (si), is adjacent to the ameloblasts (a). The discrete line visible between the stratum intermedium and the ameloblasts is not basement membrane (BM). The BM is located between the tooth and the differentiating ameloblasts (see F and G). During enamel secretion (region II), the BM is absent, but it reforms during ameloblast maturation (region III and IV). Immunostaining with mAb D3-4 shows that the laminin alpha 3 chain is expressed during ameloblast differentiation in the wild-type (D), but not the Lama3^tm1Crt/Lama3^tm1Crt (E) tooth. Cross-sections from comparable regions of wild-type (F-I and N) and mutant (J-M and O) teeth are shown for region I (F and J), region II (G and K), region III (H and L), and region IV (I and M). The double arrows in H and L are the same size to emphasize the reduced size of the mutant ameloblasts. N and O are enlargements of I and M, respectively. The white arrow marks the location where the boundary between the stratum intermedium and the ameloblasts is no longer distinguishable. At this precise location, the organization of the mutant epithelium becomes extremely disorganized (compare N and O). Abbreviations are as follows: a, ameloblasts; o, odonoblasts; bm, basement membrane; si, stratum intermedium; e, enamel; ree, reduced enamel epithelium. The cartoon in B was modified from Eisenmann (1989).

Copyright

This image is from Ryan MC, J Cell Biol 1999 Jun 14;145(6):1309-23, and is displayed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License. J:55865

Associated Alleles

Symbol	Name
Lama3^tm1Crt	laminin, alpha 3; targeted mutation 1, William G Carter

Associated Genotypes

Allelic Composition	Genetic Background
Lama3^tm1Crt/Lama3^tm1Crt	involves: 129 * C57BL/6J