The sensory system of C. elegans

Sensory neurons in C. elegans

Cilia

Axons

Dendrites Cell bodies*

AFD

AWB

Sensory neuron-specific markers

AWC

AFD AWC AWB

The morphologies of C. elegans sensory neurons are distinctive

Stimuli sensed

volatile odorants

volatile odorants

volatile odorants

temperature

pheromone

water-soluble compounds

Response mediated

attraction

avoidance

attraction

memory of cultivation temperature?

dauer development

attractiondauer development

AWA

AWB

AWC

AFD

ASI

ADF

Neuron type

Sensory neuron diversity in C. elegans

Behavioral screens for olfactory mutants

X

X

X

X

Wild-type

Mutagenize

X

X

X

X

Screen usingbehavior

Isolation of mutants defective in sensory neuron specification

AWA

AWB

AWC

MutantsWild-type

AWA AWB

AWC

Amphid neurons express distinct subsets of signaling genes

Channels OSM-9, OCR-1,OCR-2

TAX-2/4

Guanylyl cyclase ODR-1

AWA AWB

ODR-3, GPA-5GPA-6

ODR-3G proteins

Olfactory receptors STR-1, STR-220,STR-219, SRD-23

ODR-10, SRA-13

Chemicals senseddiacetyl pyrazine

trimethylthiazole2-nonanone

Anderson, 1997

Specification of neuronal subtype identitiesComponent Nature of each component

a (eg. receptor expression) a1, a2, a3…….an

b (eg. neurotransmitter expression) b1, b2, b3……bn

k (pan-neuronal)

Neuron type A a2, b3, c4……..k

Neuron type B a1, b4, c2……k

….

a2 b1 k a2 b1 k a2 b1 k a2 b1

k

UNC-42

AWA

LIN-11+?

ODR-7

ASG

LIN-11+?

AWB

CEH-37+?

LIM-4

? TTX-1

AFD

CEH-36

AWCASHASI

UNC-3? ? CEH-14 ??

Transcription factor codes specifying sensory neuron identities

ASH identity

AWC identity

AFD identity

ASE identity

AWA identity

AWB identity

LIN-11 ODR-7

CEH-37 LIM-4

CEH-36

TTX-1

CHE-1

UNC-42

(LIM-HD) (NHR)

(LIM-HD)(OTX-HD)

(PRD-HD)

(GLASS)

(OTX-HD)

(OTX-HD)

ASH

AWC

AFD

ASE

AWA

AWB

X + Y+CEH-37

LIM-4

Z

AWB-specific signaling genes

AWB

DAF-19

OSM-5

OSM-6AWC

identity

AWB cilia

DAF-19

OSM-5

OSM-6

AWA

LIN-11 A B

ODR-7

C

AWA-specific signaling genes

+ +

AWA cilia

A

B

Figure 2

L/R asymmetry

50% 50% 100%

left right

AWC ASE

CHE-1

cog-1

5’3’5’

3’

lsy-6

ceh-36

lin-49

+

ASELidentity

UNC-37 LIN-49

CEH-36

ASEL

CHE-1

cog-1 ceh-36

lin-49

+

ASELidentity

UNC-37 LIN-49

CEH-36COG-1

ASERB

A

COG-1

L/R asymmetry

3/10 Lecture (Differentiation)Class Discussion(Johnston & Hobert, 2003)QUIZ

3/14 Presentation(Li, Mo et al., 2004)Lecture(Axon guidance)

3/17 Lecture(Axon guidance)