Development of telencephalin in the human cerebrum.

Telencephalin (TLN) is a 130kDa, type 1 integral membrane glycoprotein of the immunoglobulin superfamily found in the mammalian central nervous system. TLN shows a molecular structure resembling intercellular adhesion molecules-1 and -3, and binds to the CD11a/CD18 leukocyte integrin. TLN was localized to neuronal dendrites in the telencephalic gray matter: cerebral cortex and basal ganglia. We studied immunohistochemically the expression of TLN in the developing human brain. In the hippocampus, TLN immunoreactivity appeared at 29 gestational weeks (GW), intensified subsequently, and persisted into adulthood. In the temporal cortex, labeling was weak and restricted to the cytoplasm of pyramidal neurons from 35 to 39 GW, but thereafter became diffuse and intense in the cortical layers, especially the molecular layer, by 5 months of postnatal age. The development of TLN was late compared to synaptophysin and microtubule-associated protein 2, suggesting its involvement in the functional maturation of neuronal dendrites and synapses.