Table 1. Candidate screen to identify factors required for amphid dendrite fasciculation.
Candidate genes were selected from the literature based on known roles in axon fasciculation/guidance, enrichment in amphid neurons (aenriched in AWB or AFD, [Colosimo et al., 2004]), or physical interaction with SAX-7, as shown. Animals bearing the designated alleles were subjected to dye-filling, which brightly labels six amphid neurons (AWB, ASH, ASI, ASJ, ASK, ADL), and scored with a fluorescence stereomicroscope for defasciculated amphid bundles. Two mutants exhibited gross head morphology defects concomitant with defasciculation and were not pursued further (bgross head morphology defects).
| Candidate gene | Protein information and references | Allele(s) | Animals with defasciculated amphid bundles (percent, n = 50) |
|---|---|---|---|
| Mutants with known axon fasciculation/guidance defects | |||
| dig-1 | Immunoglobulin (Ig) superfamily; among largest secreted proteins in any animal (~1300 kDa) (Burket et al., 2006; Bénard et al., 2006) |
n1321 | 24 |
| ptp-3 | LAR family protein tyrosine phosphatase (Ackley et al., 2005; Ch'ng et al., 2003) |
mu256 | 14 |
| ok244 | 0 | ||
| sax-7a | L1 family/Neuroglian (Sasakura et al., 2005; Wang et al., 2005; Zallen et al., 1999) |
ky146 | 12 |
| vab-1 | sole Eph receptor in C. elegans (George et al., 1998; Mohamed and Chin-Sang, 2006; Zallen et al., 1999) |
dx31 | 10b |
| sax-3 | Robo (Slit receptor) (Zallen et al., 1998; Zallen et al., 1999) |
ky123 | 8 b |
| cdh-4 a | Fat-like cadherin (Schmitz et al., 2008) |
rh310 | 6 |
| unc-40 a | DCC (Netrin receptor) (Hedgecock et al., 1990) |
e271 | 2 |
| fmi-1 a | Cadherin family (Najarro et al., 2012; Steimel et al., 2010) |
rh308 | 0 |
| dgn-1 a | Dystroglycan family (Johnson et al., 2006; Johnson and Kramer, 2012) |
cg121 | 0 |
| syg-1 a | IrreC/IRRE family (Shen and Bargmann, 2003) |
ky652 | 0 |
| casy-1 | Calsyntenin family (Kim and Emmons, 2017) |
ok739 | 0 |
| Other adhesion molecules enriched in amphid neurons | |||
| nrx-1 a | Neurexin family (Haklai-Topper et al., 2011) |
wy778 | 2 |
| plx-2 a | Plexin (Semaphorin receptor) (Ikegami et al., 2004; Nakao et al., 2007) |
ev773 | 0 |
| nlr-1 a | Neurexin/Caspr family (Haklai-Topper et al., 2011) |
tm2050 | 0 |
| ptp-4 a | protein tyrosine phosphatase (Thompson et al., 2013) |
gk715362 | 0 |
| rig-3 a | Ig superfamily (C. elegans Deletion Mutant Consortium, 2012) | ok2156 | 0 |
| scd-2 a | Receptor tyrosine kinase (C. elegans Deletion Mutant Consortium, 2012) | ok565 | 0 |
| igcm-1 a | Ig superfamily (C. elegans Deletion Mutant Consortium, 2012) | ok711 | 0 |
| Factors that physically interact with SAX-7 | |||
| dma-1 a | Leucine-rich repeat family (Liu and Shen, 2011) |
wy686 | 0 |
| mnr-1 | Fam151 family (Dong et al., 2013; Salzberg et al., 2013) |
wy758 | 0 |