National Avian Research Facility
National Avian Research Facility

Chameleon (Cytbow)

Ubiquitous expression of nuclear-blueFP, replaced by expression of eYFP or tdTomato or mCerulean, after CRE-mediated recombination

CPX insert
Transgenes for balanced trichromatic labeling in the Chameleon line (figure from Loulier et al. 2014).

Summary & Utility

The Chameleon chicken line provides a major opportunity for lineage tracing using several approaches. Chameleon carries a transposon vector with a complex transgene array that results in ubiquitous expression of nuclear-blueFP, which is replaced by expression of eYFP or tdTomato or mCerulean after Cre-mediated recombination. TAT-Cre recombinase can be applied to living Chameleon transgenic embryos in ovo or in EASY culture by applying bead soaked in TAT-Cre, directly via pipetting or by injection into the circulation1. In this way, it is possible to fate map tissues1,2 for example the neural crest, limb bud mesenchyme or skin. There is also the potential for Chameleon transgenic embryos to be used for tracking virus infection by viral delivery of Cre. Cre expression may also be introduced by electroporation of Cre expression plasmids or by crossing with a second, Cre-expressing transgenic line.


(A) Fibroblasts, in vitro, derived from a heterozygous Chameleon embryo after TAT-Cre recombinase protein was added to the culture medium. (B,C,D,E) TAT-Cre recombinase applied to living Chameleon embryos in ovo or in EASY culture either on a bead (asterisk in B, C, E), or directly via pipetting or injection into the circulation (D; CFP not shown). Fate mapping of the neural crest (B), limb bud mesenchyme (C) and skin (D and E). Taken from Davey et al. 2018.

Line origin

The Chameleon line is a relatively recent addition to our reporter lines, generated at the Roslin Institute, described in Davey et al. (2018). The line was generated by transfection of primordial germ cells with a transposon vector carrying the complex Cytbow transgene, kindly provided by Livet, Loulier and colleagues3. A line was selected with a single copy of the transposon inserted. Hens from this line are sterile, so we have been unable to breed birds homozygous for this insertion, resulting in the provision of eggs that are 50% Cytbow and 50% wildtype. We plan to remake this transgenic line for this reason. The original funding for the generation of this line was provided by the Wellcome Trust.

To reference this line for publications please contact Professor Helen Sang.


  1. Davey, M. G., Balic, A., Rainger, J., Sang, H. M. & McGrew, M. J. Illuminating the chicken model through genetic modification. Int. J. Dev. Biol. 62, 257–264 (2018).
  2. Ho, W. K. W. et al. Feather arrays are patterned by interacting signalling and cell density waves. PLoS Biol. 17, (2019).
  3. Loulier, K. et al. Multiplex cell and lineage tracking with combinatorial labels. Neuron 81, 505–520 (2014).