Frizzled3 controls axonal development in distinct populations of cranial and spinal motor neurons

Abstract

Disruption of the Frizzled3 (Fz3) gene leads to defects in axonal growth in the VIIth and XIIth cranial motor nerves, the phrenic nerve, and the dorsal motor nerve in fore- and hindlimbs. In Fz3−/− limbs, dorsal axons stall at a precise location in the nerve plexus, and, in contrast to the phenotypes of several other axon path-finding mutants, Fz3−/− dorsal axons do not reroute to other trajectories. Affected motor neurons undergo cell death 2 days prior to the normal wave of developmental cell death that coincides with innervation of muscle targets, providing in vivo evidence for the idea that developing neurons with long-range axons are programmed to die unless their axons arrive at intermediate targets on schedule. These experiments implicate planar cell polarity (PCP) signaling in motor axon growth and they highlight the question of how PCP proteins, which form cell–cell complexes in epithelia, function in the dynamic context of axonal growth.DOI: http://dx.doi.org/10.7554/eLife.01482.001

Partial interchangeability of Fz3 and Fz6 in tissue polarity signaling for epithelial orientation and axon growth and guidance

“…At embryonic day (E) 11.5, the thinning of the XIIth cranial and phrenic nerves that characterizes Fz3 −/− embryos (Hua et al, 2013) was rescued in both Fz3 C embryos, many of these axons enter the internal capsule, but the resulting tracts appear narrower (arrow in Fig. 4D) and some of the axons exhibit aberrant trajectories around the globus pallidus (arrowhead in Fig.…”

“…In earlier work, we characterized the stalling of dorsal motor axons at the base of both fore-and hindlimbs in midgestation Fz3 −/− embryos by determining the width of the dorsal nerve at different locations along its trajectory (Hua et al, 2013). Stalling is more Neural crest migration 3/3 0/2 2/2 0/2 complete in the hindlimb and leads to rapid death of the corresponding motor neurons in the spinal cord.…”

“…− (Wang et al, 2002), Fz3 CKO (Hua et al, 2013), Fz6 − (Guo et al, 2004), Hprt-LSL-tdTomato , K14-Cre (Dassule et al, 2000), K17-GFP (Bianchi et al, 2005), Olig2…”

“…Samples were incubated with secondary antibody in blocking solution at room temperature for 2 days with gentle endover-end rotation and then washed five times in PBST. Finally samples were dehydrated in 50% methanol/PBS and methanol, and cleared in benzyl benzoate: benzyl alcohol (BBBA) as described previously (Hua et al, 2013).…”

“…Fz6 is expressed in the skin and hair follicles, and Fz6 −/− mice exhibit a nearly complete randomization of hair follicle orientations at early times in skin development, a phenotype that resembles the phenotypes of PCP mutants in the Drosophila cuticle (Wang et al, 2006a. By contrast, Fz3 is expressed in the developing central nervous system (CNS), and Fz3 −/− mice exhibit multiple defects in axon growth and guidance, including: (1) the mis-routing of thalamocortical axons to an intra-thalamic trajectory; (2) the failure of corticothalamic axons to enter the internal capsule and reach the thalamus; (3) the absence of the corticospinal tract; (4) the randomization of spinal cord sensory axon trajectories after midline crossing; (5) the failure of some cranial motor axons to reach their muscle targets; and (6) the irreversible stalling of most hindlimb and some forelimb dorsal motor axons in the nerve plexus at the base of the limbs (Hua et al, 2013;Lyuksyutova et al, 2003;Wang et al, 2002Wang et al, , 2006c. Many of these defects are also seen in Celsr3 −/− mice (Tissir et al, 2005;Zhou et al, 2008).…”