Microtubules rich in post-translationally modified α-tubulin form distinct arrays in frog lens epithelial cells

Isolated frog lens epithelia were stained with antibodies against tyrosinated, detyrosinated or acetylated α-tubulin and observed by several means including a scanning confocal microscope. The most prominent feature of Rana pipiens lens cells was a primary cilium close to the apical surface of the cells above the centrosome. This structure was associated with microtubules rich in modified α-tubulin. The cilium was less pronounced but still discernible in the cells of another species R. ridibunda. In both species, the modified (acetylated or detyrosinated) microtubules formed arrays spatially distinct from the unmodified (tyrosinated) microtubules. The modified microtubules formed a basket of microtubules with a curly distribution around the nucleus while the tyrosinated array consisted predominantly of rather straighter microtubules running from the apical centrosome to the cell periphery, down the lateral sides of the cells and across the basal surface adjacent to the lens capsule and basement membrane. It is concluded that the organization of modified microtubules previously described for several types of cultured cells may represent a remnant of the three-dimensional perinuclear array of such microtubules described here for the cells of an intact epithelium.