Adult Cdo^−/− esophagi have mispatterned smooth muscle. (A–F) Longitudinal sections of adult Cdo^+/+ and Cdo^−/− esophagi stained with antibodies to α-SMA and with DAPI. (A and B) SMCs at the LES and esophageal ME just proximal to the LES (Eso) are fasciculated in both Cdo^+/− and Cdo^−/− mice, but the smooth muscle layer in Cdo^−/− esophagi is thinner than controls. Bars, 200 µm. (C–F) Arrangement and orientation of smooth muscle fascicles in the Eso (C and D) and LES (E and F). Individual fascicles are outlined by the white dotted lines. (C and D) In the Cdo^+/+ Eso, fascicles are stacked face to face and are perpendicular to the lumen, whereas in the ectopic smooth muscle extension in Cdo^−/− esophagi they are end-to-end and parallel to the lumen. (E and F) In the LES, fascicles are face to face and perpendicular to the lumen in both Cdo^+/+ and Cdo^−/− mice. Bars, 40 µm. (G) Quantification of the distance of between the distal-most SA⁺ cell and the LES in adult esophagi. (H) Quantification of the width of the ME in Cdo^+/+ and Cdo^−/− esophagi at the LES and in the esophageal body just distal to the skeletal–smooth boundary (Eso). (I) Quantification of the cross-sectional area of individual SMCs in the Cdo^+/+ and Cdo^−/− LES and Eso. (J) Quantification of the total number of SMCs from the skeletal–smooth muscle boundary to the EGJ from Cdo^+/+ and Cdo^−/− mice. (K) qRT-PCR analysis of skeletal muscle–specific (Myh2a and Acta1) and smooth muscle–specific (Myh11 and Tagln) genes from total Cdo^+/+ and Cdo^−/− esophagus lysates, normalized to expression of 36B4. Values in G–K are means ± SD, n = 5–6. *, P < 0.005.