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C7 vertebra homeotic transformation in domestic dogs – are Pug dogs breaking mammalian evolutionary constraints?

Brocal, J; De Decker, S; José-López, R; Manzanilla, E G; Penderis, J; Stalin, C; Bertram, S; Schoenebeck, J J; Rusbridge, C; Fitzpatrick, N; Gutierrez-Quintana, R


J Brocal

S De Decker

R José-López

E G Manzanilla

J Penderis

C Stalin

S Bertram

J J Schoenebeck

C Rusbridge

N Fitzpatrick

R Gutierrez-Quintana


The number of cervical vertebrae in mammals is almost constant at seven, regardless of their neck length, implying that there is selection against variation in this number. Homebox (Hox) genes are involved in this evolutionary mammalian conservation, and homeotic transformation of cervical into thoracic vertebrae (cervical ribs) is a common phenotypic abnormality when Hox gene expression is altered. This relatively benign phenotypic change can be associated with fatal traits in humans. Mutations in genes upstream of Hox, inbreeding and stressors during organogenesis can also cause cervical ribs. The aim of this study was to describe the prevalence of cervical ribs in a large group of domestic dogs of different breeds, and explore a possible relation with other congenital vertebral malformations (CVMs) in the breed with the highest prevalence of cervical ribs. By phenotyping we hoped to give clues as to the underlying genetic causes. Twenty computed tomography studies from at least two breeds belonging to each of the nine groups recognized by the Federation Cynologique Internationale, including all the brachycephalic ‘screw‐tailed’ breeds that are known to be overrepresented for CVMs, were reviewed. The Pug dog was more affected by cervical ribs than any other breed (46%; P 


Brocal, J., De Decker, S., José-López, R., Manzanilla, E. G., Penderis, J., Stalin, C., …Gutierrez-Quintana, R. (2018). C7 vertebra homeotic transformation in domestic dogs – are Pug dogs breaking mammalian evolutionary constraints?. Journal of Anatomy,

Journal Article Type Article
Acceptance Date Apr 11, 2018
Publication Date May 14, 2018
Deposit Date May 23, 2018
Publicly Available Date May 31, 2018
Print ISSN 0021-8782
Publisher Wiley
Peer Reviewed Peer Reviewed
Public URL


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