Sonic Hedgehog-signalling patterns the developing chicken comb as revealed by exploration of the Peacomb mutation

Henrik Boije (1) , Mohammad Harun-Or-Rashid (1) , Yu-Jen Lee (1) , Freyja Imsland (2) , Nicolas Bruneau (3) , Agathe Vieaud (3) , David Gourichon (4) , Michèle Tixier-Boichard (3) , Bertrand Bed'Hom (3) , Leif Andersson (2, 5) , Finn Hallböök (1)

1 Department of Neuroscience
2 Science for Life Laboratory, Department of Medical Biochemistry and Microbiology
3 GABI - Génétique Animale et Biologie Intégrative
4 UE PEAT - Pôle d'Expérimentation Avicole de Tours
5 Department of Animal Bredding and Genetics

The genetic basis and mechanisms behind the morphological variation observed throughout the animal kingdom is still relatively unknown. In the present work we have focused on the establishment of the chicken comb-morphology by exploring the Pea-comb mutant. The wild-type single-comb is reduced in size and distorted in the Pea-comb mutant. Peacomb is formed by a lateral expansion of the central comb anlage into three ridges and is caused by a mutation in SOX5, which induces ectopic expression of the SOX5 transcription factor in mesenchyme under the developing comb. Analysis of differential gene expression identified decreased Sonic hedgehog (SHH) receptor expression in Pea-comb mesenchyme. By experimentally blocking SHH with cyclopamine, the wild-type single-comb was transformed into a Pea-comb-like phenotype. The results show that the patterning of the chicken comb is under the control of SHH and suggest that ectopic SOX5 expression in the Pea-comb change the response of mesenchyme to SHH signalling with altered comb morphogenesis as a result. A role for the mesenchyme during comb morphogenesis is further supported by the recent finding that another comb-mutant (Rose-comb), is caused by ectopic expression of a transcription factor in comb mesenchyme. The present study does not only give knowledge about how the chicken comb is formed, it also adds to our understanding how mutations or genetic polymorphisms may contribute to inherited variations in the human face.

Mots clés: chicken; sonic hedgehog pathway; pea comb; comb development

Domaines: Biologie animale

Henrik Boije, Mohammad Harun-Or-Rashid, Yu-Jen Lee, Freyja Imsland, Nicolas Bruneau, et al.. Sonic Hedgehog-signalling patterns the developing chicken comb as revealed by exploration of the Peacomb mutation. PLoS ONE, 2012, 7 (12), Non paginé. ⟨10.1371/journal.pone.0050890.g002⟩. ⟨hal-01019833⟩