Cleft Lip and Palate in Four Full-Sib Puppies from a Single Litter of Staffordshire Bull Terrier Dogs: An Anatomical and Genetic Study

SIMPLE SUMMARY: Orofacial clefts occur due to incomplete fusion of the tissues forming the lip and palate during embryonic development. There are three categories of such cleft: cleft lip (CL), cleft palate (CP), and cleft lip and palate (CLP). Orofacial clefts are among the most common congenital malformations found in dogs. Puppies with this condition suffer aspiration pneumonia, malnutrition, failure to thrive, and death if not treated. Surgical correction of canine CLP is increasingly common. Detailed radiological anatomical studies of the skulls of affected puppies of different breeds are thus required to plan medical treatment. Moreover, genetic studies are needed to search for the genetic background of this developmental anomaly in dogs since it is well-known that orofacial clefts are caused by genetic and environmental factors. There are numerous candidate gene mutations that cause these abnormalities in mammals. These include ADAMTS20, DLX6, and MYH3, which have been examined in the present study, though no DNA variants are detected. In conclusion, the molecular background of this developmental abnormality, observed in four out of seven puppies of a single litter, remains unknown. ABSTRACT: Cleft lip and palate (CLP) is a well-known congenital defect in dogs, characterized by abnormal communication between the oral and nasal cavities. Its incidence rate is high and affects all dog breeds. The etiology of CLP is thought to be multifactorial, caused by both genetic and environmental factors. In this study, four puppies out of seven from a single litter of Staffordshire Bull Terrier dogs with craniofacial abnormalities were anatomically and genetically examined. Classical anatomical preparation, dyed-latex-injection of the arterial vessels, and cone-beam computed tomography were used. The puppies showed variations in their observable abnormalities: three of them had a complete cleft of the palate on both sides, while one puppy had a cleft on the right side only. Cytogenetic analysis showed a normal diploid chromosome number (2n = 78,XX or 78,XY) in the studied animals. Known genomic variants of CLP were examined in the ADAMTS20, DLX6, and MYH3 genes, but no mutations were identified. Further studies are needed to identify the breed-specific genetic variants associated with canine CLP.