Mucin genes in horse airways: MUC5AC, but not MUC2, may play a role in recurrent airway obstruction.
BACKGROUND
Increased mucin gene expression may be an important cause of mucus accumulation observed in recurrent airway obstruction (RAO)-affected horses. To date, however, no mucin gene sequences are available for the horse.


OBJECTIVE
To identify equine homologues of gel-forming mucins and investigate their expression at different airway generations of healthy and RAO-affected horses.


METHODS
Two equine homologues were identified by cloning and sequencing fragments of equine (eq)MUC5AC and eqMUC2.


RESULTS
Semiquantitative RT-PCR on RNA from airways (generations 1, 5, 10, 15; small airways and parenchyma), stomach (glandular), and colon revealed that eqMUC5AC is expressed in equine stomach and in all of the airway samples. In contrast, eqMUC2 steady-state mRNA levels were detected in colon and very faintly in stomach, but not in airway tissue. EqMUC5AC expression was also compared to that of ZO-1, a tight junction protein, and eqMUC5AC/ZO-1 ratios were higher in RAO-affected compared to control horses at all airway generations.


CONCLUSIONS
That eqMUC5AC is expressed in horse airways, but any expression of MUC2 is undetectable and unlikely to be of physiological consequence.


CONCLUSIONS
EqMUC5AC up-regulation may be a primary mechanism responsible for mucus hypersecretion and accumulation in RAO.
Gerber
V
V
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan 48824-1314, USA.
Robinson
N E
NE
Venta
R J
RJ
Rawson
J
J
Jefcoat
A M
AM
Hotchkiss
J A
JA
D000402:Airway Obstruction / Q000209:etiology / Q000378:metabolism / Q000662:veterinary*; D000818:Animals; D005260:Female; D015870:Gene Expression; D006734:Horse Diseases / Q000378:metabolism*; D006736:Horses; D008168:Lung / Q000378:metabolism; D008297:Male; D055271:Mucin 5AC; D055262:Mucin-2; D009077:Mucins / Q000235:genetics* / Q000378:metabolism; D009093:Mucus / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D012008:Recurrence; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D012689:Sequence Homology, Nucleic Acid; D014132:Trachea / Q000378:metabolism
D055271:Mucin 5AC; D055262:Mucin-2; D009077:Mucins; D012333:RNA, Messenger