Cell-loại hình cụ thể thay thế nối giữa các tế bào thần kinh và các tế bào myelinating tài khoản cho hai trong số các đồng dạng mối nối, đồng dạng tế bào thần kinh bao gồm một tên miền mucin, trong khi các tế bào myelinating bao gồm một tên miền FNIII thêm | Major components of myelin in the mammalian CNS and PNS 19 of the protein. Cell-type specific alternative splicing between neurons and myelinating cells accounts for two of the splice isoforms neuronal isoforms include a mucin domain while myelinating cells include an additional FNIII domain Southwood et al. 2004 Tait et al. 2000 . At least two promoters have been identified and may confer relative cell-type specific expression in neurons and oligodendrocytes unpublished . Nfasc is a type I glycoprotein with a single transmembrane domain. It is an IgSF member belonging to the L1 subgroup and typically contains six Ig domains and three FNIII domains in its extracellular region. Although Nfasc has been studied because of its neurite outgrowth promoting activity and participation in axon-axon interactions Volkmer et al. 1996 it has most recently been characterized with regard to its roles in myelination and node of Ranvier formation. In the CNS both the neuronal and myelin isoforms of Nfasc are targeted to paranodal regions of myelin sheaths where they participate in formation of axoglial junctions along with contactin and Caspr Sherman et al. 2005 Tait et al. 2000 . Neuronal splicing of the Nfasc gene encodes a 186 kD form of the protein NF186 while oligodendrocytes and Schwann cells synthesize NF 155. NF186 is also targeted to nodes of Ranvier where it may participate in macromolecular complexes to stabilize the association of astrocyte processes with the nodal axonal membrane. In the PNS NF155 synthesized by Schwann cells is targeted to myelin paranodes and axons target NF186 only to nodes of Ranvier. Deletion of the Nfasc gene in mice results in the absence of axoglial junctions at myelin paranodes the failure of Schwann cell microvilli adhesion to the nodal axon reduced saltatory conduction in a subpopulation of myelinated fibers and early death Sherman et al. 2005 . Myelin lipids Traditionally scholarly contributions from brain lipid research to our .
