Mucin genes in horse airways: MUC5AC, but not MUC2, may play a role in recurrent airway obstruction.

Authors: Gerber V, Robinson N E, Venta R J, Rawson J, Jefcoat A M, Hotchkiss J A

Journal: Equine veterinary journal

DOI: 10.2746/042516403776148291 PubMed: 12755427Log in to save

Summary

# Mucin Gene Expression and Recurrent Airway Obstruction in Horses Recurrent airway obstruction (RAO) is characterised by excessive mucus accumulation in affected horses' airways, yet the underlying molecular mechanisms remained poorly understood. Gerber and colleagues identified equine homologues of two gel-forming mucin genes—MUC5AC and MUC2—and used semiquantitative RT-PCR to measure their expression across different airway generations (from proximal to distal), alongside stomach and colon tissue from both healthy and RAO-affected horses. EqMUC5AC was expressed throughout the respiratory tract in all airway samples, whilst eqMUC2 expression was confined to the colon and showed only faint expression in stomach tissue with no detectable airway expression. When comparing eqMUC5AC expression to ZO-1 (a tight junction protein marker), diseased horses demonstrated significantly elevated eqMUC5AC/ZO-1 ratios across all airway generations compared to controls. These findings suggest that MUC5AC up-regulation—rather than MUC2—represents the primary mucin involved in pathological mucus hypersecretion during RAO, offering a potential therapeutic target for managing this common obstructive airway disease in equine practice.

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Practical Takeaways

•RAO in horses appears to involve specific mucin gene over-expression (MUC5AC) rather than abnormal expression of multiple mucins, suggesting targeted therapeutic approaches may be possible
•Understanding MUC5AC as a key molecular driver of RAO mucus accumulation could inform development of new management strategies beyond current anti-inflammatory and environmental control measures
•Mucin gene expression profiling may eventually help identify RAO-affected horses or predict disease severity, though clinical applications are not yet available

Key Findings

•eqMUC5AC is expressed in all equine airway generations but eqMUC2 is not detectably expressed in airway tissue
•eqMUC5AC/ZO-1 ratios are significantly higher in RAO-affected horses compared to control horses across all airway generations
•eqMUC5AC up-regulation may be the primary mechanism responsible for mucus hypersecretion and accumulation in RAO

Conditions Studied

recurrent airway obstruction (rao)mucus accumulation in airways

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