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. 2021 Jun 11;218(4):iyab086. doi: 10.1093/genetics/iyab086

Figure 2.

Figure 2.

Neuronal maintenance defects in the sax-7 mutant alleles qv30, qv25, and qv26. (A) sax-7S is required to maintain head ganglia organization postdevelopmentally. Fluorescence images of the head region of 1-day-old adults, where the soma and axons of the chemosensory neurons ASH and ASI are visualized using reporter Psra-6::DsRed2. Drawings illustrate microscopy images. Reporters Psra-6::DsRed2 (hdIs29) and Psra-6::gfp (oyIs14) give comparable results for all genotypes tested. In the wild type, the soma of neurons ASH/ASI (red arrowheads) are positioned posteriorly relative to the nerve ring (yellow arrowhead) throughout stages. In sax-7 mutants, the relative positioning between the soma of neurons ASH/ASI and the nerve ring is initially normal (soma posterior to nerve ring), but becomes progressively defective in late larvae onwards (soma can either overlap with or become anterior to the nerve ring). Quantification of the relative positioning between the ASH/ASI soma and the nerve ring in wild type, null mutant qv30, and sax-7S-specific mutants qv25 and qv26. Animals were examined at the 2nd (L2) and 4th (L4) larval stages, as well as at days 1, 2, or 5 of adulthood. Rescue of qv30 null mutant defects by expression of sax-7S(+) in the nervous system using the heterologous promoters Punc-14 and Prab-3. “#1, #2, #3” indicate independent transgenic lines. Statistical comparisons are with qv30 mutant. (B) sax-7S is required to maintain the retrovesicular ganglion organization. Fluorescence images showing the soma of two pairs of interneurons AVK and AIY on either sides of the 1-day-old adult animal visualized using reporters Pflp-1::gfp and Pttx-3::DsRed2. In the wild-type animals, the soma of AVK (green) and AIY (red) are adjacent with each other. In sax-7 mutants, one or both of the AVK and AIY neuron pairs become separate from one another. Quantification of animals showing separate pairs of AVK and AIY soma in wild type, qv30, qv25, and nj48, at the 4th larval stage (L4) and days 1 and 2 of adulthood. (C) sax-7S functions to maintain tail ganglia organization. Fluorescence images of the chemosensory neurons PHA and PHB in L4 larvae, visualized using DiI staining, whose soma are located in the lumbar ganglia on each side of the animal. In the wild type, the PHA and PHB soma are adjacent to each other. In sax-7 mutants, one or both of the PHA/PHB pairs are separated from one another. Quantification of disorganized soma position in wild type, qv30, qv25, and nj48, at L4. (D) sax-7S is required to maintain axon position within the ventral nerve cord. Fluorescence images of the interneurons PVK (visualized using oyIs14). PVQ axons extend ipsilaterally along the ventral nerve cord during embryogenesis. In the wild type, each PVQ axon remains on the ipsilateral side of the ventral nerve cord. In sax-7 mutants, while PVQ axons develop normally and are positioned like wild type at birth (early 1st larval stage), they later become displaced to the opposite side of the ventral nerve cord. Quantification of displaced PVQ axons in wild type and qv30, at hatching (early L1 stage) and the 4th larval stage (L4). Scale bars, 10 μm. Sample sizes are indicated under each column of the graph. Error bars are the standard error of the proportion. Asterisks denote significant difference: *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001 (z-tests, P-values were corrected by multiplying by the number of comparisons, Bonferroni correction). “+” indicates wild-type strain; n.s., not significant.