Development of a strain of rabbits with congenital simple nonsyndromic coronal suture synostosis. Part I: Breeding demographics, inheritance pattern, and craniofacial anomalies.

The lack of an animal model of congenital coronal suture (CS) synostosis has prompted the widespread use of an experimental rabbit model using adhesive immobilization of the CS. Such postnatal models have helped make significant scientific contributions but may still not fully represent all aspects of the human congenital condition. In the March 1993 issue of The Cleft Palate-Craniofacial Journal we reported a female rabbit born in our laboratory with complete bilateral CS synostosis. This follow-up study presents our attempts to breed this animal and establish a strain of craniosynostotic rabbits. To date, we have accomplished 10 back- and intercrosses with these animals and have produced a total of 71 live offspring; 10 animals exhibited complete nonsyndromic unilateral (plagiocephalic) or bilateral (brachycephalic) CS synostotic deformities at birth, and 19 animals exhibited partial CS synostosis that showed more than 75% growth retardation across the CS (well below the 95% confidence interval for normals). Results revealed that gestational time and litter size averages were consistent with those reported for the strain, although the average litter size decreased with increased inbreeding. By 1.5 weeks of age the completely synostosed animals already exhibited brachycephalic cranial vaults and midfacial hypoplasia compared to unaffected siblings. Initial pedigree analysis suggested an autosomal dominant inheritance pattern with incomplete penetrance and variable expressivity. The development of such a congenital rabbit model may prove useful in helping to understand the etiopathogenesis of this condition in human populations.