Worm Breeder's Gazette 12(4): 51 (October 1, 1992)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Identification of the Cues Used to Generate Blastomere Diversity: The Role of the P2 -EMSInteraction in Positioning Gut Fate into E

Bob Goldstein

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Center for Developmental Biology, Zoology Department, University of Texas, Austin, Texas 78712

The gut of C. elegans derives from all the progeny of the E cell, a cell of the eight cell stage (Sulston et al. 1983 Dev. Biol. 100:64.) In order for E to form gut, EMS must contact P2 during the four cell stage (Goldstein 1992 Nature 357:255; [See Figure].)

P2 'sposition on the "E" side of EMS raises the possibility that the P2 -EMSinteraction is the cue that makes E different from MS. Alternatively, the E and MS sides may be different from each other before the P2 -EMSinteraction, such that only the E side can form gut in response to the interaction. In order to determine which is the case, I tried to move P2 to the MS side of EMS, to see if MS then forms gut. This is a particularly frustrating manipulation. A more feasible way to address the question turned out to be isolating P2 and EMS, and then placing the two cells back in contact in a random orientation. If any side of EMS can form gut in response to the interaction, then gut should always form from the daughter of EMS that contacts P2 .If however only the E side can form gut, then in some cases either gut will form from the daughter away from P2 or gut will not differentiate. Fortunately, P2 and EMS stick immediately upon contact and they do not rotate around each other when placed back together, precluding the possibility that P2 moves back to its original position. Which daughter of EMS formed gut was then determined by one of two methods: In five cases cell division times were watched to see which daughter took on E-like cell division timings, and in another five cases the daughters of EMS were separated from each other and cultured individually to see which produced gut granules. Gut differentiated from the side of EMS on which P2 was placed in all ten cases. This result indicates that any side of EMS can form gut in response to the induction, and hence that the interaction with P2 is what makes E different from MS. Current work is aimed at identifying cellular mechanisms by which the induction makes E different than MS, and determining whether cell interactions are required at other stages for gut fate to be segregated into E.

Literature Cited:

Sulston et al. 1983 Dev. Biol. 100:64.

Goldstein 1992 Nature 357:255.

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