Fig. 3. Injection of morpholinos specific to notch1, deltaD, her1 or deltaC perturbs somite formation. Embryos injected with (A) notch1^mo (four experiments; n=201; 97% affected) or (B) deltaD^mo (four experiments; n=127; 99% affected) form the anterior seven to nine somites but fail to make regular posterior segments. (C,D) Dorsal views of her1^mo1 (4 experiments n=200; 91% affected) or deltaC^mo1 (6 experiments; n=545; 78% affected) injected embryos, respectively. In contrast to aei/deltaD and des/notch1, her1 and deltaC are necessary for the formation of both the anterior and posterior somites. Arrowheads in D indicate the misplaced somite borders. (E-P) The expression patterns of her1 and deltaC seen in wild-type, bea and morpholino-injected embryos. These embryos are between the 8 and 12 somite stages. Anterior is upwards. (E,K) Wild-type expression patterns of her1 and deltaC, respectively. Injection of Notch1^mo causes defects in her1 expression (F) (two experiments; n=133; 100% affected) and deltaC expression (L) (two experiments; n=38; 100% affected) identical to that observed in des embryos. Injection of deltaD^mo recapitulates the pattern of gene expression that is observed in aei/deltaD embryos (not shown). Injection of deltaC^mo1 disrupts her1 expression (G) (four experiments; n=109; 98% affected) and deltaC expression (M) (6 experiments; n=168; 100% affected). Injection of a second deltaC morpholino, deltaC^mo2, that does not overlap the sequence of deltaC^mo1, produces the same defect in the expression of both her1 (H) (four experiments; n=145; 100% affected) and deltaC (N) (four experiments; n=187; 100% affected). Conversely, a control morpholino identical to deltaC^mo1, except for four nucleotide substitutions, deltaC^moC, has no effect on the expression of either her1 (I) (three experiments; n=62; 0% affected) or deltaC (O) (3 experiments; n=56; 0% affected). (J,P) Expression of her1 and deltaC, respectively, in bea^M98B embryos. bea^M98B embryos were collected from a mating of homozygous bea^M98B adults. deltaD expression is the same in all of the mutants and knockdown embryos, with the exception of 15% of fss embryos, as previously noted (not shown) (Holley et al., 2000). For F-H and L-N, percentages are in reference to n, the number of pre-sorted morphologically affected embryos examined. The specificity of the individual morpholinos is illustrated by the fact that: (1) both the deltaD^mo and notch1^mo phenocopy their known mutant phenotypes; and (2) deltaC^mo1 and deltaC^mo2 produce the identical phenotype, while deltaC^moC produces no phenotype.

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