Analysis of genomic copy number variation in equine recurrent airway obstruction (heaves)
Authors: Ghosh S., Das P. J., McQueen C. M., Gerber V., Swiderski C. E., Lavoie J.‐P., Chowdhary B. P, Raudsepp T.
Journal: Animal Genetics
Summary
# Editorial Summary Recurrent airway obstruction (heaves) is a complex inflammatory condition affecting the equine respiratory tract, yet its genetic basis remains incompletely understood; this research investigated whether copy number variants (CNVs)—segments of DNA present in differing quantities across individuals—contribute to disease susceptibility. Using genomic microarray analysis of 16 RAO-affected and 6 healthy control horses, researchers identified 245 CNV regions across the equine genome, including 48 previously unknown variants, and validated findings through quantitative PCR in an expanded cohort. A loss on chromosome 5 involving the *NME7* gene showed suggestive association with RAO (P = 0.03; corrected P = 0.06), a particularly relevant finding given *NME7*'s critical role in ciliary function and its involvement in primary ciliary dyskinesia in humans—implicating impaired mucociliary clearance as a potential disease mechanism. Although other CNVs involved genes recognised in human asthma and chronic obstructive pulmonary disease (notably the serpin family), these did not significantly differentiate affected from healthy horses, highlighting RAO's genetic heterogeneity. These findings provide initial evidence that genomic variation warrants further investigation as a factor in RAO susceptibility, though larger, well-characterised populations will be necessary before CNV profiling could offer clinical utility for breeding decisions or risk stratification.
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Practical Takeaways
- •Genetic testing for NME7 loss on chromosome 5 may eventually help identify RAO-susceptible horses, though current evidence is preliminary and requires larger population studies before clinical implementation
- •RAO appears to be a complex, heterogeneous disease with multiple genetic factors rather than single gene control, making breeding recommendations based on current data premature
- •Understanding genetic predisposition to RAO could inform selective breeding programmes and help identify at-risk individuals earlier in life
Key Findings
- •245 copy number variant regions (CNVRs) identified across equine genome, including 48 novel variants not previously documented
- •30 CNVRs found exclusively in RAO-affected horses, with suggestive association (P=0.03) between RAO and loss on chromosome 5 involving NME7 gene critical for ciliary function
- •NME7 loss represents potential genetic marker for RAO susceptibility but requires validation in larger cohorts
- •SPI2/SERPINA1 genes showed significant variation among horses but no significant difference between RAO cases and controls despite human association with COPD and asthma