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. 2020 Sep 8;29(18):3081–3093. doi: 10.1093/hmg/ddaa199

Figure 5.

Figure 5

Diminished 22q11.2 gene dosage in LgDel+/− embryos destabilizes CN V sensory and motor axon growth. (A) 2D renderings of 3D reconstructions of WT proximal (left) and distal (right) segments of CN V md sensory axons labeled after distal Ba1B injection identified by direct continuity with CNgV cell bodies of origin. Arrows: similar directions of growth for WT distal and proximal axons. Arrowheads: bifurcation of CN V sensory axon proximal/central branches. Inset: 2D renderings of a confocal image stack of CN V sensory neurons and their distal/proximal axons. (A′) 2D rendering of two WT CN V md sensory neurons showing relatively linear extension of distal and proximal axons (e.g. axon segment indicated between the two arrowheads) (B) 2D renderings of LgDel+/− CN V md sensory axons and CNgV parent cell bodies; distal and proximal LgDel+/− segments have more diverse directions of growth (arrows) than WT counterparts. Inset: 2D image of a CN V sensory axon and parent cell body. (B′) Apparently increased tortuosity (e.g. axon segment between arrowheads) of LgDel+/− CN V distal and proximal sensory axons. (C) 2D renderings of WT CN V motor axons from motor neurons. After an ~90° turn upon exiting the hindbrain (arrowheads), the axons extend directly toward Ba1B. Insets: Representative images of WT CN V motor neurons. (D) 2D renderings of LgDel CN V motor axons. Some CN V motor neuron axons (asterisks) diverge substantially from the WT pattern of hindbrain exit and direct extension toward Ba1B. Inset: Representative images of LgDel+/− motor neurons with varying degrees of axon misrouting. (E, E′) Digital enlargement and Imaris-generated reconstruction showing local branching of a LgDel+/− CN V axon. (F, F′) Digital enlargement and Imaris-generated reconstruction showing terminal sprouting of a LgDel+/− CN V axon. (G) Quantitative summaries of phenotypic frequencies (branching: br; misrouting: m; sprouting: sp; left,*P = 0.02, no phenotype: np;) and tortuosity (right,  **P = 0.003) for all individual WT (n = 56 axons) and LgDel+/− (n = 84 axons/18 embryos) CN V axons (sensory and motor). (H) Phenotypic frequencies (left) and tortuosity (right) for WT (n = 30 axons) and LgDel+/− (n = 43 axons) CN V sensory axons. (I) Phenotypic frequencies (left) and tortuosity (right) for WT (n = 26 axons) and LgDel+/− (n = 41 axons) CN V motor axons. (J, K) Schematic of major features of early WT and LgDel+/− CN V sensory and motor axon growth.