Overactivation of the Notch Pathway by NICD Causes Somite Boundary Defects After a Long Delay
NICD overexpression was induced by 30-min heat shock in hsp70:Gal4VP16;UAS:myc-notch1aICD transgenic embryos.
(A,A′) One hour after the end of a heat shock (delivered at the 16-somite stage), her4 expression is strongly induced in the neural tube and other tissues, including the PSM (C,C′).
(B) An embryo heat-shocked at 10 hpf, showing disturbances of somite boundary formation only after a long delay (as with DAPT treatment). The start of the boundary defects is marked by the arrow.
(D,D′) Embryos heat-shocked at the five-somite stage, fixed 2.5 h later, and stained by ISH for her1.
(E,E′) Embryos heat-shocked at the 16-somite stage, fixed 3 h later, and stained by ISH for her7. For both her1 and her7, the stripy pattern seen in the controls is replaced by more uniform expression in the transgenic embryos, implying a breakdown of synchronized oscillation. Note that the levels of her1 and her7 expression in the transgenic embryos are lower than the peak levels in the normal controls. For each case in (A) to (E), at least 14 embryos were examined and typical specimens were selected for this illustration.
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