Extracellular Matrix Molecules and Palate Fusion in TGF-β3 Null Mice

TGF-β3 null mice show from complete to submucous cleft palate depending on the strain where the gene targeting was performed, revealing differences in palatal shelf adhesion/fusion. Previous work by this research group demonstrated changes in the presence/distribution of extracellular matrix molecules (ECM) in the palatal medial edge epithelium (MEE) of C57BL/6J TGF-β3 null mice. Objectives: To determine whether: 1.- the changes observed are under the influence of TGF-β3 and affect palatal shelf adhesion/fusion; 2.- there are any differences in the presence/distribution of ECM molecules in the MEE of TGF-β3 null mice from a C57BL/6J (bearing complete cleft palate) and Albino-Swiss (where the middle third of the palate is adhered) strains, that may explain the different MEE adhesion. Methods: 1.- Immunolabelling with antibodies against fibronectin, laminin, and collagens IV and IX of paraffin sections from embryonic day 14.5 (E14.5) C57 BL/6J and Albino-Swiss wild type and TGF-β3 null mutant mice, and from palate cultures obtained from E14 TGF-β3 null mutants with and without the addition of TGF-β3. 2.- Addition of anti-fibronectin blocking antibody to E13.5 mouse palates and measurement of the resulting MEE adhesion and fusion. Results: When compared to the wild type, changes in the presence/distribution of fibronectin, laminin, and collagens IV and IX are observed in the null MEE from both strains, although they are striker in the strain showing complete cleft palate. Blocking fibronectin action in palate cultures leads to a decrease in palatal shelf fusion and adhesion depending on the blocking antibody concentration. Conclusion: The presence/distribution of some ECM molecules in the MEE is altered in the cleft palate presented by TGF-β3 null mice from two different genetic backgrounds, what likely contributes to the appearance of this condition. This work was supported by grants from Comunidad Autónoma de Madrid (08.6/ 0001.1/2003) and Fondo de Investigación Sanitaria (PI030185).