102
Brain Development
AP
Maternal effect genes
Gap genes
Pair-rule genes
Segment polarity genes
Homeotic genes
(a)
Expression at anterior domains
Expression at posterior domains
Drosophila
Mouse
3
3
5
5
Antenapedia complex
Bithorax complex
Chr 6
Chr 11
Chr 15
Chr 2
a1
a2
a3
a4
a5
a6
a7
b1
b2
b3
b4
c4
d4
d3
d1
b5
c5
b6
c6
b7
b8
b9
c8
c9
c10
c11
c12
a9
a10
a11
a13
b13
c13
d8
d9
d10
d11
d12
d13
lab
pb
Dfd
Scr
Ubx
AbdA
AbdB
Antp
(b)
Neural crest cells
Trigeminal nerve
Facial nerve
Vagus nerve
Glossopharyngeal
nerve
BA1
BA2
BA3
r1
r2
r3
r4
r5
r6
r7
Anterior
Krox20
Kreisler
(MafB)
a1 b1 a2 b2 a3 b3 d3 b4
A2 A7
A4/B3 B2
Hox
genes
B1 B2 B3
Eph
Ephrin
Kreisler
Hoxa3
Hoxa1
Hoxb3
Hoxa2
Hoxb2
Krox20
EphA7
EphA4
OV
(c)
unit in the chicken embryo. Then, what
molecular machinery is involved in the
hindbrain compartmentalization? First of
all, differential af±nities among compart-
mental units have been suggested. The
expression of several transcription fac-
tors such as
Hox
genes, Krox20, and
Krisler/MafB
are
known
to
delineate
rhombomere units (Fig. 7c). Downstream
of these transcription factors, several cell
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