Organisation and maturation of the human thalamus as revealed by CD15

The distribution of the CD15 antigen (CD15, 3-fucosyl-N-acetyl-lactosamine, Lewis x) has been studied immunohistochemically in the fetal human thalamu s. Its changing patterns could be related to three successive, but overlapp ing, periods primarily due to its association with radial glial cells, neur opil, and neural cell bodies, respectively. From 9 weeks of gestation (wg), a subset of CD15-positive radial glial cells distinguished the neuroepithe lium of the ventral thalamus, a characteristic also seen in the developing mouse. Distal processes of the radial glial cells converged at the root of the forebrain choroid tenia, which was also CD15 positive. From 13 wg until approximately 20 wg, CD15-positive neuropil labeling marked the differenti ation areas of prospective nuclei within the dorsal thalamus and progressiv ely outlined their territories in a time sequence, which appeared specific for each nucleus. CD15 labeling of differentiating nuclei of the ventral, m edial, anterior, and intralaminar thalamic divisions showed a transient top ographic: relationship with restricted areas of the ventricular wall. After 26 wg, CD15 immunoreactivity was observed in subpopulations of glial cells and neurons. Transient CD15 immunoreactivity was also found in delimited c ompartments within the subventricular region. The time of CD15 expression, its location, and cellular association suggest that CD15 is involved in seg mentation of diencephalon, in the specification of differentiating nuclear areas and initial processes regarding the formation of intercellular contac ts and cellular maturation. J. Comp. Neurol. 437: 476-495, 2001. (C) 2001 W iley-Liss, Inc.