Evaluation of CHD7 as a candidate gene for choanal atresia in alpacas (Vicugna pacos)

Choanal atresia (CA) is a craniofacial malformation characterized by obstruction of the posterior nasal aperture, resulting in laborious respiratory inspiration and exhalation. Alpaca crias with CA typically develop fatal pneumonia, frequently as the result of milk aspiration during nursing, and euthanasia is usually inevitable. Nonsense or missense mutations in the CHD7 gene cause a comparable condition (CHARGE syndrome) in humans. In this study, the coding region of CHD7 was sequenced in six CA-affected alpacas. Forty-nine sequence variants were identified, of which 10 would result in amino acid changes (non-synonymous), some with potentially deleterious effects. However, none of the observed variants would result in the obvious deleterious effects caused by nonsense or missense mutations. Although a role for CHD7 mutations in CA cannot be definitively dismissed, these do not appear to be the primary cause of CA in alpacas.