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Fig. 3. Vhnf1 participates in a multistep process to repress r4 identity in r5 and
r6. Wild-type (wt; left column), val– (middle
column) and vhnf1– (right column). (A-C)
krox20 (blue) in r3 and r5 of wt (A), with a small dorsal stripe in
the r5 territory of val– embryos (B) compared with
the variable dorsal and ventral expression in vhnf1–
embryos (C). (D-L) Repression of hoxb1a (blue) in r5 and r6 requires
multiple genes. hoxb1a is initially downregulated posterior to r4
(asterisks) at 10.7 hpf in wt (D), val– (E) and
vhnf1– (F) embryos. By 11.7 hpf hoxb1a
expression is largely restricted to r4 in wt (G) and
val– (H) embryos but is upregulated posterior to r4
in vhnf1 mutants (I). At 18-20 hpf hoxb1a is clearly
expanded in vhnf1 mutants (L) and mildly expanded in val
mutants (K) compared with wt (J). (M-R) fgf3 (blue) expression is
similar between wt (M), val– (N) and
vhnf1– (O) embryos at 10.5 hpf. By 11.7 hpf
fgf3 is normally only highly expressed in r4 (P), while in
vhnf1 mutants (R) its expression expands posteriorly. (S-U)
Expression of the RA-metabolizing enzyme cyp26b1 is restricted to r4
and r3 at 12 hpf in wt (S) val– (T) and
vhnf1– (U) embryos. Expression of fgf8 is
also limited to r4 and anterior by 12 hpf in wt (V)
val– (W) and vhnf1– (X)
embryos. (Y-AA) A single pair of Mauthner cells is present in r4 of wt (Y) and
val– (Z) embryos, while supernumerary Mauthner cells
are detected in 58% of vhnf1– embryos (AA;
arrowhead). A-C are lateral views with anterior to the left and dorsal to the
top. D-AA are dorsal views with anterior to the left. krox20
expression in r3 and r5 is in red (D-X). The mid-hindbrain boundary (MHB) is
marked by pax2.1 (blue, J-L; red, M-O) or en3 (red,
P-R).
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