Figure 8
From: Fgf receptor 3 activation promotes selective growth and expansion of occipitotemporal cortex
A model for the mechanisms of cortical area formation regulated by Fgf signaling. (a) S ummary of cortical area positioning upon manipulation of Fgf signaling. Anterior over-expression of Fgf8 caudally shifts cortical areas, while sequestration of Fgf8 activity by ectopic expression of a truncated Fgfr3 protein (sFgfr3) leads to a rostral shift [6]. In the current study, a genetic model of biochemically active Fgfr3 kinase domain mutant (Fgfr3*) showed a 'rostral' shift of cortical areas, likely to have resulted from a massive surface area expansion selectively occurring in caudal cortical areas. The area positions of Fgfr3 knockout (ko) mice are currently unknown. Cont, control; Wt, wild type. (b) We hypothesize that, being expressed in a unique graded pattern at the outset of neurogenesis, Fgfr3, together with other Fgf receptor members, may regulate formation of cortical areas, mediating signals from multiple Fgf ligands with distinct functions and diverse expression patterns. This study indicates that various proliferative parameters, including Tc (namely TG1), proliferative capacities of the cortical progenitors, and radial glia and intermediate progenitor cell populations, could be regulated along the Fgfr3 expression gradient. Therefore, Fgf signaling regulates cortical area formation by controlling both patterning and cell proliferative properties.