Fig. 4. Notch signaling defects in Mib1–/– embryos.
(A) Lateral view of E8.75
9.0 wild-type (wt; a-h) and
Mib1–/– (mt; a'-h') embryos probed
for Dll1 (a,a'), Jag1 (b,b'), Notch1
(c,c'), Notch2 (d,d') Lfng (e,e'),
Hes1 (f,f'), Hes5 (g,g') and Hey1
(h,h') expression. There is ectopic overexpression of Dll1 in
the neural tube (a'; asterisk) and the downregulation of
Dll1 in the somite and PSM (a; arrows, a'; arrowhead); loss of
Jag1 expression in the head, branchial arches and presomitic region
(b; arrows, b'; arrowhead); loss of Notch1 and Notch2
expression in somites (c,d; arrows, c',d'; arrowheads); and
ectopic overexpression of Notch1 in the neural tube and trigeminal
ganglia (c'; asterisk); the loss of Lfng expression in the
trigeminal ganglia, newly forming somites and PSM (e'; arrowheads); and
the loss of Hes1, Hes5 and Hey1 expression in the first
branchial arches and PSM (Hes1, f'; arrowheads), the forebrain
and neural tube (Hes5, g'; arrowheads), and the first branchial
arches and newly forming somites (Hey1, h'; arrowheads) of the
Mib1–/– embryos. (B) Expression of Notch
target genes (Hes1, Hes5, Hes7, Hey1, Hey2, Heyl) and Notch pathway
genes [Notch1, Notch2, Neur, RBP-j
, Pres1 (presenilin
1), Pres2 (presenilin 2), Maml1 (mastermind-like1),
Dll1, Jag1 and Mib1]. Total RNA from E8.5 wild-type (wt) and
Mib1–/– (mt) embryos was analyzed by RT-PCR.
ß-actin was used for normalization. The results are representative of
three independent experiments. (C) Real-time quantitative RT-PCR for
Notch1, Dll1, Jag1, Hes5, Hey1 and Hey2, using RNA from E8.5
wild-type (white bars) and Mib1–/– (black
bars) embryos. Numbers in each bar indicate the mean fold of induction, and
error bars indicate the standard deviation. ***P<0.0001,
**P<0.001.