High Resolution Immuno-Electron Microscopy Reveals That Fetal Skin Contains Microfibrils which are Heteropolymers of Fibrillin-1 and Fibrillin-2

Immunolocalization studies of neonate and older human tissues have previously demonstrated that fibrillin-1 is a component of elastin and non-elastin associated microfibrils. In sections taken from fixed, dehydrated and embedded tissue, microfibrils appear in the transmission electron microscope as hollow rods, 6-8 nm in diameter. When isolated from tissue by homogenization and observed following negative staining or rotary shadowing, microfibrils appear as beaded strings with a degree of extendibility. Recently, a closely related glycoprotein, fibrillin-2, has been described, which is expressed in early fetal development, prior to fibrillin-1, but then disappears in most tissues just prior to birth. We demonstrate here the characterization monoclonal antibodies specific for fibrillin-2. The antibodies are shown by ELISA and immunoblots to be fibrillin-2 specific. The matrix from a variety of tissues, including aorta, tendon, and eye are shown to contain fibrillin-2 by immunofluorescence in a pattern similar to that of fibrillin-1.