Fig. 1.

Spliced XBP1 is expressed in laminitic tissues. a. Representative immunoblots probed for expression of the XBP1s or XBP1u proteins derived from spliced and unspliced XBP1 mRNA, respectively. XBP1s is prevalent in EL front limbs (F) and barely detectable in either EL hind limbs (H) or controls (C). Membranes were reprobed for vinculin as a loading control. Four pairs of EL front and hind limbs from the same horses are noted by horizontal bars and numbered 1–4 (pair 1: 116 LF, RH; pair 2: 141 LF, RH; pair 3: 134 RF, RH; pair 4: 104 RF, 104 RH; see Table 1). b. The antibody to XBP1 recognized a band of the same mw in both Hela (human) cells and equine lamellar tissue. c PCR amplification of a region near the XBP1 splice site produces amplimers of the expected base pairs for spliced and unspliced XBP1. Samples are labeled as in (a). d,e. Immunoblot band intensities for XBP1s were measured and normalized as described in Methods. d Box blot summarizing XBP1s expression levels in control (n = 7), EL front (n = 12) and EL hind limbs (n = 7). Horizontal lines represent the median value for each group. XBP1s expression was not significantly different between control and EL hind limbs (p = 0.08). e Comparison of XBP1s expression levels in paired samples from EL front and EL hind limbs of the same horses (n = 7 pairs), inset shows the 3 sample pairs with similar XBP1s band intensities between front (F) and hind limb (H). Although the differences between front and hind limbs are smaller, the same pattern is apparent as that in pairs having much greater variation