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Fig. 4. ceh-20 and unc-62 affect cell positioning along the AP
axis. (A) In the double mutant mig-13(mu31); egl-20(n585), QR.pax
cells were displaced further posteriorly than in mig-13(mu31) or
egl-20(n585) single mutants. QR descendants actively migrated towards
the posterior in many of these double mutants animals. (B,C) QR.pax cells
could be displaced to a location posterior to the birthplace of QR in double
mutants ceh-20(mu290); egl-20(mu320) and unc-62(mu232);
egl-20(mu320), but not in double mutants ceh-20(mu290);
mig-13(mu31) or unc-62(mu232); mig-13(mu31). The penetrance of
mig-13(mu31) phenotypes is equal to that of the molecular null,
mu225 (Sym et al.,
1999). egl-20(mu320) is likely a null allele
(Ch'ng et al., 2003). Double
mutants of ceh-20(mu290) or unc-62(mu232) with a strong
allele of egl-20, n585, also displayed QR descendants migrating
posteriorly instead of anteriorly (histogram not shown). In ceh-20(mu290);
egl-20(n585) or unc-62(mu232); egl-20(n585) double mutants, 24%
or 13%, respectively, of QR.pax cells were located in the posterior body
between V5.a and V6.a. Distributions of QR.pax cells in ceh-20(mu290),
unc-62(mu232), egl-20(mu320) and mig-13(mu31) single mutants are
also shown. There is no significant difference in the QR.pax distributions
between ceh-20(mu290) and ceh-20(mu290); mig-13(mu31)
(P>0.05). (D) QR.pax cells were displaced further posteriorly in
lin-39(n1760); egl-20(mu320) and lin-39(mu26); mig-13(mu31)
double mutants than in lin-39(n1760), egl-20(mu320) or
mig-13(mu31) single mutants. However, QR descendants did not actively
migrate towards the posterior in these double mutants. The mutation in
lin-39(mu26) is predicted to eliminate DNA-binding activity, whereas
lin-39(n1760) is a null allele lacking the homeodomain
(Clark et al., 1993;
Wang et al., 1993).
lin-39(mu26) and lin-39(n1760) single mutants have nearly
identical QR.pax distributions. The vertical gray line indicates the
birthplace of the QR cell. The pink arrow indicates the total anterior
distance traversed by QR and its descendants giving rise to QR.pax in
wild-type animals. The green arrows denote active posterior migration of cells
giving rise to QR.pax. n=100 cells for each strain.
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