The chicken limb (wings) develops and buds out from the lateral plate mesoderm at typical locations along the sides of the embryo. These limbs grow with regional specification that includes distinct anterior-posterior and dorsal-ventral pattern. The limb buds out because of the interaction between the mesenchyme and apical ectodermal ridge (AER). The signals sent from the AER maintain the progress zone in the mesenchymal layer. The progress zone has cell in highly proliferative and undifferentiated state. This knowledge can be used to produce higher number of chicken wings from fewer chickens.
There are certain compounds that are known to induce limb formation. These compounds are secreted by the AER, since it is observed that removal of AER causes cessation of limb formation. The easiest option is to extract the chemical compounds from the AER and then apply these on the chick embryo to produce higher number of wings. The other option is to induce wing formation using chemical signals similar to that of compounds secreted by AER. The two different methods would be as follows:
- Fibroblast growth factor (FGF):
The best nominee for inducing limb formation would be the family of fibroblast growth factor (FGF). FGF-4 is expressed in copious amounts by AER during the growth of limbs in chick embryo. Application of FGF-4 or FGF-8 on the embryo has shown to generate limb in chicken. Thus, FGF can be applied as beads over on the entire mesenchymal layer of the embryo could produce limbs (Figure 1). The FGF also interacts with the mesenchymal layer to for a zone of polarizing activity (ZPA) that forms the regional specification of the extra wing formed. The genes for FGF can also be over-expressed to induce the production of extra limbs in chick embryo (Cohn et al., 1995).
- Retinoic acid (RA):
Retinoic acid (RA) is synthesized in the limb bud of the embryo, and excessive production of RA induces limb duplications. Stratford et al. (1996) reported that RA organizes new outgrowths of limb tissues on the anterior sides of the embryo; which results in the formation of limbs with double posterior structure. Therefore, RA can be applied directly as FGF proteins to induce limb development in the chick embryo.
These two tools from the knowledge of developmental biology can be applied for production of higher number of wings from fewer numbers of chickens. Biotechnology tools like animal tissue culture and genetic modification can also be employed to produce larger number of chicken wings with minimum number of chickens.
- Cohn, M.J., Belmonte, J.C., Abud, H., Heath, J.K. and Tickle, C. (1995) Fibroblast Growth Factors Induce Additional Limb Development from the Flank of Chick Embryos. Cell, Vol. 80, 739-746.
- Tanaka, E. and Gann A. (1995) The budding role of FGF Current Biology, 5 (6): 594-597.
- Stratford, T., Horton, C. and Maden, M. (1996) Retinoic acid is required for the initiation of outgrowth in the chick limb bud. Current Biology, 6 (9): 1124–1133