Figure 6.

Three types of sensory neurons form T- or Y-shaped branches controlled by CNP/Npr2-mediated cGMP signaling: MTN, CSG, and DRG. (A) Scheme summarizing previous data and this study on the expression profile of Npr2/cGKI in embryonic neurons: MTN, CSG, and DRG are positive for both components. Localization of the ligand CNP in the hindbrain and dorsal spinal cord is illustrated in dots in (A). (B₁) Absence of the CNP/Npr2 signaling system caused axon bifurcation errors in these three types of neurons. CSG, cranial sensory ganglia; DRG, dorsal root ganglia; Fb, forebrain; Mb, midbrain; MTN, mesencephalic trigeminal neurons; Hb, hindbrain; r1, rhombomere1; SC, spinal cord; Vmo, trigeminal motor nucleus. (B₂) Scheme of the circuit of major axon branches of MTN in Npr2 mutants illustrating the reduced sensory feedback to motor neurons in Vmo of the hindbrain. See also Figure 3B for wild type.