A candidate gene for choanal atresia in alpaca

Abstract

Choanal atresia (CA) is a common nasal craniofacial malformation in New World domestic camelids (alpaca and llama). CA results from abnormal development of the nasal passages and is especially debilitating to newborn crias. CA in camelids shares many of the clinical manifestations of a similar condition in humans (CHARGE syndrome). Herein we report on the regulatory gene CHD7 of alpaca, whose homologue in humans is most frequently associated with CHARGE. Sequence of the CHD7 coding region was obtained from a non-affected cria. The complete coding region was 9003 bp, corresponding to a translated amino acid sequence of 3000 aa. Additional genomic sequences corresponding to a significant portion of the CHD7 gene were identified and assembled from the 2× alpaca whole genome sequence, providing confirmatory sequence for much of the CHD7 coding region. The alpaca CHD7 mRNA sequence was 97.9% similar to the human sequence, with the greatest sequence difference being an insertion in exon 38 that results in a polyalanine repeat (A12). Polymorphism in this repeat was tested for association with CA in alpaca by cloning and sequencing the repeat from both affected and non-affected individuals. Variation in length of the poly-A repeat was not associated with CA. Complete sequencing of the CHD7 gene will be necessary to determine whether other mutations in CHD7 are the cause of CA in camelids.

Clinical Findings and Survival in 56 Sick Neonatal New World Camelids

“…The high number of congenital defects in neonatal NWC has been observed in other studies . The 2 main defects found in this study were, as previously reported, choanal atresia and vulvar deformity . Although choanal atresia can be corrected, this study suggests that the presence of this defect is associated with a poor outcome.…”

“…The poor prognosis of NWC with congenital defects could be associated with the purpose of the animals presented. The presence of congenital defects might limit the value of an animal as some defects, like choanal atresia, have been shown to have a genetic component . .…”

Lactation and Neonatal Care

“…[35][36][37] Surgical correction of choanal atresia has been attempted, but euthanasia should be considered because of the high rate of complications and their effects on quality of life. 38 38 …”

Thoracic Imaging and Respiratory Surgery

“…High frequencies allow only superficial structures to be imaged, but at higher resolution and image quality than those of low frequency. 39 The study was not able to definitively determine the genetic abnormality that causes CA but did sequence the CDH7 gene in alpacas for further study. With large adult camelids, low frequency (4-5 MHz) convex or sector transducers are typically favored for thoracic imaging.…”