ASKL, ASKR

Type: Sensory neuron (chemosensory (gustatory), pheromone-sensory, electrosensory and photosensory)
In MoW: ASK
Male Wiring Project: ASKL, ASKR
In Wormbase: ASK, ASKL, ASKR
Lineage: AB alpppapppa, AB praaaapppa
Location: Lateral ganglia of head
Description: Amphid neurons, single ciliated endings. Like all other amphid neurons, ASK are born near the presumptive nose of the embryo during development. They then anchor a short projection there, after which the cell body migrates away, stretching the dendrite out behind it. This process is dependent on DEX-1 or DYF-7, secreted extracellular matrix proteins which act cooperatively for anchoring. In mutants lacking these proteins, the dendrite fails to anchor at the nose and is dragged along with the migrating cell body, giving rise to a short dendritic stub (Heiman and Shaham, 2010). Dendritic process takes up FITC. ASK axon projects into the ventral cord by way of the same side amphid commissure and then grows into the nerve ring where it makes diverse synaptic connections in ring neuropil.
Neurotransmitter/ Neuropeptide:
- Glutamate
- FLP-21
- NLP-8
- NLP-10
- NLP-14



- Possibly PDF-1; pigment dispensing factor homolog
(Barrios et al, 2012; Li and Kim, 2008; Nathoo et al., 2001; Lee et al., 1999)
Innexin expression:
- INX-18
- INX-19
(Altun et al., 2009; Chuang et al, 2007)
Receptor expression:
- OSM-9; TRPV (transient receptor potential channel, vanilloid subfamily; mammalian capsaicin receptor-like channel)-cation selective channel
- SRA-7; G protein-coupled serpentine receptor
- SRA-9; G protein-coupled serpentine receptor
- SRG-2; G protein-coupled serpentine receptor
- SRG-8; G protein-coupled serpentine receptor
- DAF-11; transmembrane guanylyl cyclase
(Birnby et al., 2000; Troemel et al., 1995; Colbert et al., 1997)
Function:
- Involved in chemotaxis to lysine (Bargmann and Horvitz, 1991).
- ASH, ADL, ASK and ASE sensory neurons are responsible for avoidance from certain chemical repellents. ASH plays a major role in this avoidance, whereas ADL, ASK and ASE play minor roles that are only evident when ASH is missing (Hiliard et al., 2002; Sambongi et al., 1999; Bargmann et al, 1990.) Mediate avoidance behavior from protons, detergents, alkaloids such as quinine; ASH is the main sensory neuron responsible for quinine detection while ASK plays a minor role (Hilliard et al, 2004).
- After animals are removed from bacterial food, they initiate a local search behavior consisting of reversals and deep omega-shaped turns. This is followed by dispersal ~30 min later, as reversals and turns are suppressed. Local search behavior is triggered by AWC, ASK and AIB neurons while dispersal is promoted by ASI and AIY neurons (Gray et al., 2005).
- Sense pheromone and are involved in behavioral responses to pheromone (C. elegans pheromone is a mixture composed of derivatives of the dideoxysugar ascarylose (C3, C6, C7, C9 and other ascarosides) that regulates entry to dauer stage at L1, as well as adult behaviors such as sexual attraction of males to hermaphrodites and social behavior, i.e., attraction between hermaphrodites to clump into feeding groups) (Jang et al., 2012; Lockery, 2009; Macosco et al., 2009). ADF, ASI and ASG inhibit entry into dauer stage while ASJ and ASK promote dauer entry (Kim et al., 2009; Ouellett et al., 2008; Schackwitz et al., 1996; Bargmann and Horvitz, 1991). ASK pair is one of the three core sensory neurons (AWA, AWC, ASK) that are required for sexual-attraction in males (White and Jorgensen, 2012).
- Lightsensation (350-470 nm range); when a flash of light is focused on the head of a worm moving forward, the animal halts and initiates reversals. Ablation of ASJ, AWB, ASK and ASH neurons together leads to a severe deficit in this head avoidance response while ablation of them individually or in different combinations does not yiled a significant defect suggesting functional redundancy (Ward et al., 2008).
- Electrosensory navigation; C. elegans moves toward the negative pole of an electric field. Killing the ASJ or ASH neurons leads to significant disruption in electrotaxis while killing ASK, AWB or AWC has a weaker effect (Gabel et al., 2007).


Click image for closeup view Click pictures for higher resolution images. Also see DiI staining of ASK in dorso-ventral view; DiI staining of ASK in lateral view.

 
 

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ASKL (AB alpppapppa) development in the embryo.
Dorsal view. Bottom is left side of the embryo. Spheres indicate individual nuclei. Black sphere: ancestors of ASKL (since last ASKL ancestor has not yet gone through its final division, the black sphere seen at the end of this movie is still AB alpppappp); dark grey spheres: apoptotic cells; other cells follow the WA color code (after they acquire specific cell or tissue identities). 0 min is fertilization. Click on the movie for higher resolution rendition (by A. Santella & Z. Bao).

 
 

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ASKR (AB praaaapppa) development in the embryo.
Dorsal view. Bottom is left side of the embryo. Spheres indicate individual nuclei. Black sphere: ancestors of ASKR (since last ASKR ancestor has not yet gone through its final division, the black sphere seen at the end of this movie is still AB praaaappp); dark grey spheres: apoptotic cells; other cells follow the WA color code (after they acquire specific cell or tissue identities). 0 min is fertilization. Click on the movie for higher resolution rendition (by A. Santella & Z. Bao).


 
 

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3D reconstruction of the anterior sensory endings (cilia and dendrites) from high resolution serial section transmission electron micrographs (ssTEMs).
Bar 1 μm. Color code for the sensory endings is shown on the right-colors do not follow the WA color code. To expand, double click on the video, to return to original size, click "esc" (Doroquez et al., 2014)

 
 
 

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3D reconstruction of all amphid neuron cilia and associated socket and sheath cell processes.
Modeled from serial section transmission electron micrographs
(ssTEMs). Bar 1 μm. Color code for the sensory endings is shown on the left-colors do not follow the WA color code. To expand, double click on the video, to return to original size, click "esc" (Doroquez et al., 2014)

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