Ortholog-specific Spatial Expression of Vanins in the Respiratory Tract of Horses

Equine asthma (EA) is the most prevalent chronic respiratory disease in horses, but molecules thought to be relevant in its pathogenesis are not yet fully understood. Recently, increased Vanin-1 (VNN1) levels were found in bronchoalveolar lavage fluid from horses with severe EA. Human VNN1 is known as a pantetheinase, which is associated with respiratory diseases such as asthma, but the equine vanins (eVNNs) are uncharacterized. We identified the domain architecture of eVNN in silico and analyzed its tissue expression in healthy horses using RT-PCR (n=5) and in situ hybridization (n=3). Recombinant eVNNs were expressed in HEK293 cells to assess cellular transport and glycosylation via Endo H and PNGase F treatment. Three putative functional eVNNs were identified on chromosome 10, each containing canonical Nitrilase superfamily domains. All genes showed a broad tissue expression, but distinct airway localization: eVNN1 and eVNN2 were predominantly expressed in respiratory epithelium, whereas eVNN3 was localized in submucosal glands. eVNN1 and eVNN3 were secreted, while eVNN2 remained cell associated. Pantetheinase activity of recombinant eVNN1 was confirmed by mass spectrometry. The three eVNNs appear to cover different functional niches in equine airways, enabling future research into their putative role in EA.