English: Model of the Role of Netrin-1 Signaling in the Topography of Thalamocortical Projections in the Ventral Telencephalon of the Mouse

(B and C). A high-rostral to low-caudal gradient of Netrin-1 in the ventral telencephalon (VTel) plays a critical role in the topographic projection of dorsal thalamus (DTh) axons in the VTel. Rostromedial domain of the DTh expresses high levels of DCC and that the caudolateral domain of the DTh expresses low levels of DCC. This gradient is required for both the attraction of rostral dorsal thalamus (DTR) axons and the repulsion of caudal dorsal thalamus (DTC) axons to the Netrin-1–rich rostral domain of the VTel. Unc5A and B are expressed preferentially in the caudolateral domain of the DTh and Unc5C is expressed in a high-caudolateral to low-rostromedial gradient in the DTh. Unc5A/C are required for the repulsion of caudal DTh axons from the Netrin-1–rich domain of the VTel, but they do not play any significant role in the projection of rostromedial DTh axons. Also over-expression of Unc5C in DTR axons is sufficient to convert their outgrowth into DTC outgrowth, i.e., repulsion away from the Netrin-1–rich rostral domain of the VTel.

A1, primary auditory area; GE, ganglionic eminence; M1, primary motor area; S1, primary somatosensory area; V1, primary visual area.