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Fig. 4. Donor neural crest can also delay molecular and histogenic programs of
cranial feather development. (A) Duck cranial neural crest cells follow their
own timetable for differentiation when transplanted into quail hosts.
Resultant duail chimeras collected at HH36 contain feather buds as well as
epidermal regions that lack placodes (broken outline). The absence of
epidermal placodes is equivalent to that observed on control embryos at HH33
(compare with Fig. 2G). (B,C)
The presence and absence of cranial feather buds can be seen in sections
stained histologically with trichrome (TC). (D) Immunohistochemical analyses
using an anti-quail antibody confirm that wherever placodes are present, the
dermis is derived from quail host neural crest (Q¢PN positive, black
cells). (E) By contrast, regions that lack placodes contain dermis derived
from the duck donor (Q¢PN negative). (F,G) Bmp4 is expressed in
mesenchyme derived from the quail host but is not yet detected in mesenchyme
of duck donor origin. (H,I) Shh is expressed in the epithelium
overlying dermis from the quail host but not over dermis derived from the duck
donor. (J,K) Delta1 is detected in quail host dermis but not in duck
donor-derived dermis. (L) Duail chimeras collected at HH39 have normal long
feather buds alongside areas containing short feather buds like those observed
on HH36 controls. (M) Immunohistochemical analyses confirm that the short
feather buds, which are like those of a HH36 duck instead of a HH39 quail, are
derived from duck donor neural crest (Q¢PN-negative). (N) Long feather
buds composed of quail host epidermis (Q¢PN-positive) and duck donor
dermis (Q¢PN-negative; arrow) are present in duail chimeras at HH42. Scale
bar: 1 mm in A; 100 µm in B-K; 1 mm in L; 50 µm in M; 100 µm in
N.
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