Involved in neural development, regulating the establishment of proper connectivity within the nervous system. May play a role in the establishment of the anterior-posterior axis during gastrulation. Regulates the differentiation of oligodendrocytes and myelination of axons. May function as a cellular signal transducer (By similarity). Homodimer; disulfide-linked (Probable). May also form heterodimer with either TENM1 or TENM2 or TENM3 (By similarity). Mainly expressed in the brain. During gastrulation, expressed throughout the embryo very faintly. Expressed along the anterior margin of the neural plate. Later, this marginal expression extends caudally, and eventually restricted only to the caudal neural plate. At 14 hours post-fertilization, it is expressed in the brain. Expressed in the rhombomere 5 (r5) and more strongly in r6. Expressed in the rostral diencephalon with weak expression in the optic vesicles, and a region covering the mesencephalon and the midbrain/hindbrain boundary (MHB) in a gradient manner with stronger expression at its posterior end. At 17 hpf, expressed weakly in the dorsal edge of the most caudal part of the neural tube. Faint expression is detected in several neurons located at ventral and dorsal parts of the caudal spinal cord. EGF-like domains 2 and 5 which have an odd number of cysteines might enable the formation of intermolecular disulfide bonds. Cytoplasmic proline-rich regions could serve as docking domains for intracellular SH3-containing proteins. Morpholino knockdown of the gene in embryos resulted in a modest reduction of myelin in the brain and an increase in the number of small-diameter neuronal axons with aberrant branching along the notochord. Belongs to the tenascin family. Teneurin subfamily.