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Fig. 3. Cranial neural crest regulates histogenic and molecular programs of feather
morphogenesis. (A) At HH33, there are no cranial feather buds in either duck
or quail (not shown) as stained histologically with trichrome (TC). (B,C)
However, in chimeric `quck' at HH33, the dermis is derived from quail donor
neural crest (Q¢PN positive, black cells), which is on a faster timetable
for development and induces premature formation of feather buds in duck host
epidermis. The extent of differentiation, size and spacing of these quck
feather buds are more like that observed in D, a HH36 control quail instead of
an HH33 duck, which is the host species. (E) Control duck do not form short
feather buds until HH36. (F) In situ hybridization analyses reveal that
molecular markers of feather development such as bmp4 are not
expressed in the capital tracts of control quail and duck prior to HH34. (G,H)
However, chimeric quck at HH33 express bmp4 in cranial feather
mesenchyme, which is equivalent to that observed for control quail at HH36.
(I,J) HH33 quck express bmp2 in the epithelium and mesenchyme like
HH36 quail. (K,L) HH33 quck express follistatin in the epithelium and
mesenchyme like HH36 quail. (M,N) HH33 quck express bmpr1a in the
epithelium and mesenchyme like HH36 quail. (O,P) HH33 quck express
shh in the epithelium like HH36 quail. (Q,R) HH33 quck express
ptc in the epithelium and mesenchyme like HH36 quail. (S,T) HH33 quck
express delta1 in the mesenchyme like HH36 quail. (U,V) HH33 quck
express notch1 in the epithelium and mesenchyme like HH36 quail. (W)
At HH31, there are no epidermal placodes or underlying dense dermis present in
control duck or quail (not shown). (X) These do not appear in control quail
and duck (not shown) until HH34 (arrow). (Y,Z) However, in chimeric quck at
HH31, quail donor neural crest-derived mesenchyme has given rise to dense
dermis (Q¢PN positive) and has induced epidermal placodes (arrows) of duck
host origin (Q¢PN negative). (A',B') In situ hybridization
analyses reveal that bmp4 and bmp2 are expressed in quail
donor-derived mesenchyme prematurely at HH31, whereas normally they would not
be expressed until HH34 (arrows). Other mesenchymal and epithelial molecular
markers of feather morphogenesis are not yet detected except for
bmpr1a and notch1, which are expressed continuously from at
least HH29 in most tissues (data not shown). Scale bar: 100 µm.
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