Developmental expression of GAP-43 and SNAP-25 in heterotopic rat cortical grafts

In situ hybridization techniques were used to assess (i) whether the temporal developmental profiles of the nervous system specific growth associated phosphoprotein (GAP-43) and the 25-kDa synaptosomal-associated protein (SNAP-25) are maintained in heterotopic cortical transplants, and (ii) whether the hybridization intensity in morphologically differentiated heterotopic transplants is comparable to that in the cortex of host animals. Cortical primordia at embryonic day 14 were stereotactically grafted into the striatum of adult recipient rats. Grafts at days 4, 7, 14, 35 and 56 after transplantation demonstrated developmental changes with a progressive decline of GAP-43 and a continuous up-regulation of SNAP-25 expression. Our data provide evidence of distinct molecular alterations during the differentiation process of cortical grafts, which are strikingly similar to previous studies investigating the temporal profile and intensity of GAP-43 and SNAP-25 gene expression in normal developing cortex of the rat.