Neural development of the neuregulin receptor ErbB4 in the cerebral cortex and the hippocampus: Preferential expression by interneurons tangentially migrating from the ganglionic eminences

The receptor tyrosine kinases represent an important class of signal transduction molecules that have been shown to play critical roles in neural development. We report in the present study that the neuregulin receptor ErbB4 is preferentially expressed by interneurons that are migrating tangentially from the ventral to the dorsal rat telencephalon. ErbB4 immunoreactivity was detected in the medial ganglionic eminence as early as embryonic day (E) 13 at the inception of tangential migration. Prominent ErbB4-positive migratory streams consisting of cells double-labeled with ErbB4 and Dlx, a marker of tangentially migrating cells, were found to advance along the lower intermediate zone and the marginal zone from the ventrolateral to the dorsomedial cortex at E16-E18. After E20, the ErbB4-positive stream in the lower intermediate zone shifted towards the germinal zone and further extended via the cortex into the hippocampal primordium. ErbB4 was not expressed by Tbr1-positive glutamatergic projection neurons during development. ErbB4 was preferentially expressed by the majority of parvalbumin-positive interneurons and subsets of other GABAergic interneurons in the cerebral cortex and the hippocampus in adulthood. The early onset and preferential expression of ErbB4 in tangentially migrating interneurons suggests that neuregulin/ErbB4 signaling may regulate the development and function of telencephalic interneurons.