Worm Breeder's Gazette 13(2): 98 (February 1, 1994)

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.

What happens to E when it doesn't make gut

Bob Goldstein

Figure 1

MRC-LMB, Hills Road, Cambridge CB2 2QH, England

The E lineage in C. elegans is induced to form gut by an interaction between P(2) and EMS early in the four-cell stage(1). Normally P(2) contacts the side of EMS which gives rise to the E lineage, however the other side of EMS also is competent to respond to gut induction: moving P2 to the opposite side of EMS causes gut to form from what normally would have been the MS lineage. (2) Here I discuss recent results concerning how E and MS differentiate in the absence of gut induction, to address what the "uninduced state" of EMS is, and to determine if MS is also affected by the P(2)-EMS interaction.

EMSs were isolated at various times in the four-cell stage and were cultured overnight. Isolates were examined for birefringent rhabditin granules, and then were processed for either an esterase histochemical stain or for immunohistochemistry. The progeny of induced EMSs (isolated late) formed gut as assayed by rhabditin granules, esterase stain and ICB4 antibodies, body wall muscle as assayed by antibodies to paramyosin, and pharyngeal muscle as assayed by 3NB12 antibodies. No hypodermis was formed, as assayed by antibodies to LIN-26 .This suite of cell types is consistent with EMSs normal fate,(3) E forming gut, and MS forming mostly pharyngeal muscle and body wall muscle.

The progeny of uninduced EMSs (isolated early) formed about twice as much body wall muscle and pharyngeal muscle as induced EMSs, but no gut and no hypodermis. This suite of cell types suggests that both daughters of EMS are differentiating as MS lineages, and is consistent with previous results concerning the lineage timing of uninduced EMSs.(l)

Each daughter of EMS was examined similarly to see if each do in fact form body wall muscle and pharyngeal muscle in the absence of gut induction. Again EMSs were isolated at various times in the four-cell stage, only this time after EMS divided once, the two daughters were separated and were cultured independently. lnduced EMSs (isolated late) formed all gut from one daughter, and body wall muscle and pharyngeal muscle but no gut nor hypodermis from the other daughter, consistent with one acting as an E lineage and the other as an MS lineage. Uninduced EMSs (isolated early) formed two daughters both of which formed body wall muscle and pharyngeal muscle, and no gut nor hypodermis, consistent with both acting as MS lineages.

These results and the experiment in which P(2) was moved to the other side of EMS imply that induction by P(2) is the cue that males one side of EMS differentiate differently than the other side. The results also suggest that this induction affects only E and not MS; the uninduced state of EMS is essentially as an "MSMS" cell. It is interesting then that the induction occurs before EMS divides to form E and MS; gut induction appears to affect only part of a single responding cell. Additionally the results lend further support to the notion that the MS suite of cell types form independently of cell interactions with for example the gut lineage or with ABa or ABp derivatives.(4)

Figure 1