Basal lamina fibronectin

Many of the extracellular materials are filaments made from fibrous proteins, mainly collagen and elastin, and adhesion proteins such as fibronectin and laminin. Collagens form a family of proteins with a tissue-specific distribution, including types inifound in connective tissue such as filamentsand types IV and Vfound in basal laminae forming sheets of tissue. 

Fibronectin and laminin are the principal adhesive glycoproteins in connective tissues and basal laminae (the structures underlying tissues that form sheets), respectively. Adhesive glycoproteins link the outer surfaces of cells... 

One way in which crest cells could disperse is by locomotion, which would be dependent on the appearance of structural and adhesive environmental features. The only candidate for these is the ECM, which contains a variety of interstitial and basal lamina-related adhesion molecules, such as fibronectin (FN), laminin (LN) and collagens (see Section 6). 

The basal lamina surrounding the abluminal surface of the endothelial cell is composed of type IV collagen, heparan sulfate, fibronectin, and laminin. Laminin acts as a charge barrier and interacts with integrins to regulate permeability of the BBB and cellular transport across it [5]. 

The basement membrane provides a structural barrier to extravasation of cellular blood elements and anchors endothelial cells to astrocytes. In BBB it contains extracellular matrix (ECM) molecules, such as laminin, type IV collagen, and fibronectin. Most of these are substrates for a family of neutral proteases called MMPs, especially MMP-2 and MMP-9. More than twenty MMPs and four of their TIMPs act together to control tighdy temporally restricted, focal proteolysis of ECM. They are also implicated in opening the BBB, and increased MMP production may injure the BBB, at least in part through their proteolytic activity at the tight junctions of brain endothelial cells and the BBB basal lamina. 

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