Gato A, Martinez M L, Tudela C, Alonso I, Moro J A, Formoso M A, Ferguson M W J, Martínez-Alvarez C
Departamento de Anatomía Humana, Facultad de Medicina, Universidad de Valladolid, Valladolid 47005, Spain.
Dev Biol. 2002 Oct 15;250(2):393-405.
In mammals, the adhesion and fusion of the palatal shelves are essential mechanisms in the development of the secondary palate. Failure of any of these processes leads to the formation of cleft palate. The mechanisms underlying palatal shelf adhesion are poorly understood, although the presence of filopodia on the apical surfaces of the superficial medial edge epithelial (MEE) cells seems to play an important role in the adhesion of the opposing MEE. We demonstrate here the appearance of chondroitin sulphate proteoglycan (CSPG) on the apical surface of MEE cells only immediately prior to contact between the palatal shelves. This apical CSPG has a functional role in palatal shelf adhesion, as either the alteration of CSPG synthesis by beta-D-Xyloside or its specific digestion by chondroitinase AC strikingly alters the in vitro adhesion of palatal shelves. We also demonstrate the absence of this apical CSPG in the clefted palates of transforming growth factor beta 3 (TGF-beta(3)) null mutant mice, and its induction, together with palatal shelf adhesion, when TGF-beta(3) is added to TGF-beta(3) null mutant palatal shelves in culture. When chick palatal shelves (that do not adherein vivo nor express TGF-beta(3), nor CSPG in the MEE) are cultured in vitro, they do not express CSPG and partially adhere, but when TGF-beta(3) is added to the media, they express CSPG and their adhesion increases strikingly. We therefore conclude that the expression of CSPG on the apical surface of MEE cells is a key factor in palatal shelf adhesion and that this expression is regulated by TGF-beta(3).
在哺乳动物中，腭突的黏附和融合是继发腭发育过程中的关键机制。这些过程中任何一个出现故障都会导致腭裂的形成。尽管浅表内侧边缘上皮（MEE）细胞顶端表面存在丝状伪足似乎在相对的MEE细胞黏附中起重要作用，但腭突黏附的潜在机制仍知之甚少。我们在此证明，硫酸软骨素蛋白聚糖（CSPG）仅在腭突接触前立即出现在MEE细胞的顶端表面。这种顶端CSPG在腭突黏附中具有功能性作用，因为β-D-木糖苷改变CSPG合成或软骨素酶AC对其进行特异性消化都会显著改变腭突的体外黏附。我们还证明，在转化生长因子β3（TGF-β(3)）基因敲除突变小鼠的腭裂中不存在这种顶端CSPG，而在培养中将TGF-β(3)添加到TGF-β(3)基因敲除突变的腭突中时，它会与腭突黏附一起被诱导。当鸡的腭突（在体内不黏附，在MEE中也不表达TGF-β(3)和CSPG）在体外培养时，它们不表达CSPG且部分黏附，但当向培养基中添加TGF-β(3)时，它们会表达CSPG且黏附显著增加。因此，我们得出结论，MEE细胞顶端表面CSPG的表达是腭突黏附的关键因素，且这种表达受TGF-β(3)调控。
