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Results: 4

1.
Figure 3

Figure 3. LIN-14, but not LIN-28 or HBL-1, is responsible for blocking 2° fate specification in lin-4(0) mutants. From: LIN-14 inhibition of LIN-12 contributes to precision and timing of C. elegans vulval fate patterning.

(A) Reduction of lin-14 activity, but not lin-28 or hbl-1 activity, restores expression of the 2° fate marker nIs106[lin-11p::gfp] in lin-4(0) mutants.
(B) lin-14(n355) hypermorphic mutants exhibit a lateral signaling defect. 1° fate markers were expressed in lin-14(n355) mutants, but the 2° fate marker nIs106[lin-11p::gfp] was not. + = lin-14(+).

Ji Li, et al. Curr Biol. ;20(20):1875-1879.
2.
Figure 1

Figure 1. The 1° fate is specified normally, but the 2° fate is not, in lin-4(0) mutants. From: LIN-14 inhibition of LIN-12 contributes to precision and timing of C. elegans vulval fate patterning.

Scoring of markers and complete genotypes of strains shown in these figures are given in Supplemental Experimental Procedures.
(A) P6.p adopts the 1° fate in lin-4(0) mutants. "lin-4 gonad ablated": the L1 gonad was ablated in lin-4(0) mutants.
(B) All VPCs respond to EGFR-Ras-MAPK signaling in lin-4(0). The 1° fate marker used was ayIs4[egl-17p::gfp]. Note also that the penetrance of 1° marker expression increases in P5.p and P7.p, consistent with loss of lateral signaling.
(C) Direct transcriptional targets of LIN-12, which mark the 2° fate, are not expressed in lin-4(0) mutants. Another 2° fate marker, nIs106[lin-11p::gfp], is also not expressed in lin-4(0) ([12]; see Fig. 2A).

Ji Li, et al. Curr Biol. ;20(20):1875-1879.
3.
Figure 2

Figure 2. lin-4(0) blocks the effects of constitutive LIN-12 activity, but not cleavage or nuclear access of the LIN-12 intracellular domain. From: LIN-14 inhibition of LIN-12 contributes to precision and timing of C. elegans vulval fate patterning.

(A) lin-4(0) suppresses the ectopic expression of the 2° fate marker nIs106[lin-11p::gfp] caused by constitutively active LIN-12. In addition, the Multivulva phenotype caused by lin-12(n137) and LIN-12(intraΔP) expressed in VPCs was completely suppressed by lin-4(0). For arEx1080, 100% (99/99) of lin-4(+) hermaphrodites had at least one ectopic pseudovulva but 0% (0/86) of lin-4(0) had a pseudovulva; for arEx1094, 99% (87/88) of lin-4(+) hermaphrodites but 0% (0/35) of lin-4(0) hermaphrodites had a pseudovulva.
(B) Nuclear accumulation of the GFP-tagged LIN-12 intracellular domain appears to be unaffected in lin-4(0) mutants.

Ji Li, et al. Curr Biol. ;20(20):1875-1879.
4.
Figure 4

Figure 4. LIN-14 and temporal gating of LIN-12 activation. From: LIN-14 inhibition of LIN-12 contributes to precision and timing of C. elegans vulval fate patterning.

(A) High lin-14 activity near the time of lateral signaling blocks 2° fate specification. lin-4(0); lin-14(n355n679ts) has a highly penetrant lateral signaling defect at 15° that is relieved at 25°. Reducing lin-14 activity up to the L2 molt permits lateral signaling. See Supplemental Experimental Procedures for details. ***, p < 0.001; N. S., not significant (Fisher's exact test).
(B) Reduction of lin-14 activity in the L2 stage removes the normal block to constitutive lin-12 activity. A comparable level of arIs107[mir-61p::yfp] expression in the L3-stage VPCs in lin-12(n137) mutants was obtained in the L2-stage VPCs when lin-14 was reduced by growth at 25° during the L2 stage. **, p < 0.01; N. S., not significant (Fisher's exact test). We note that arIs107[mir-61p::yfp] was chosen for this experiment because it is specifically expressed in response to the lateral signal in P5.p and P7.p at the L3 stage; other markers display more dynamic patterns until the Pn.px stage and hence could not be used here.
(C) Anatomical configuration of lag-2-expressing cells ([32]; X. Zhang, X. Karp and I. G., unpublished observations) with respect to the VPCs in the L2 and L3 stages.
(D) Representation of the relationship between lin-4, lin-14 and lin-12. Left, lin-14 activity in the L2 stage may prevent premature activation of LIN-12 by ligands produced by other cells such as neurons in the local environment. When lin-14 activity is further lowered in the L3 stage, LIN-12 can activate its targets upon receiving the lateral signal produced by P6.p. Right, schematic representation of gene activity over time. lin-14 activity is represented by a dashed line because we do not know whether it decreases as a step function upon lin-4 expression or gradually.

Ji Li, et al. Curr Biol. ;20(20):1875-1879.

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