Transmembrane protein required for proper cognitive functions. Involved in the development of dentate gyrus (DG) neuron circuitry, is necessary for AMPA receptors surface expression and proper excitatory postsynaptic currents of DG granule neurons (PubMed:28096412). Regulates the organization and stability of the microtubule network of sensory neurons to allow axonal transport. Through the interaction with DST, mediates the docking of the dynein/dynactin motor complex to vesicle cargos for retrograde axonal transport (PubMed:17287360). In hippocampal neurons, required for BDNF-dependent dendrite outgrowth (PubMed:21849472). Cooperates with SH3GL2 and recruits the WAVE1 complex to facilitate actin-dependent BDNF:NTRK2 early endocytic trafficking and mediate signaling from early endosomes (PubMed:21849472, PubMed:27605705). Interacts with DST (isoform 1) (PubMed:17287360). Interacts with SH3GL2 (PubMed:21849472). Interacts (via N-terminus) with CYFIP1 and CYFIP2; the interactions associate TMEM108 with the WAVE1 complex (PubMed:27605705). Expressed in the nervous system tissues, such as hippocampus and spinal cord, is barely detectable in peripheral tissues such as heart, lung, liver, kidney and muscle (PubMed:17287360, PubMed:28096412). In brain, highly expressed in dentate gyrus neurons and expressed in cortex, olfactory bulb, ammon's horn, cerebellum, hypothalamus and striatum (PubMed:28096412, PubMed:21849472). In brain, detectable as early as 12 dpc and the level increases persistently through later embryonic stages to the adult age (PubMed:17287360). In the hippocampus, undetectable at postnatal day 1 (P1), detected at P7, the levels peak between P15 and P21 to remain at a high level during adulthood (PubMed:28096412). Glycosylated. Mutants are viable and show no difference in body weight or locomotor activity (PubMed:28096412). They are impaired in sensorimotor gating, spatial recognition memory and suppressed fear memory consolidation (PubMed:28096412). Spine density of dentate gyrus granule neurons is significantly reduced compare to wild-type animals, which is associated with decreased spine width and increased spine length (PubMed:28096412).