A Novel Terminal Web‐Like Structure in Cortical Lens Fibers: Architecture and Functional Assessment

Abstract

This study describes a novel cytoskeletal array in fiber cells of the ocular lens of the rat and shows its relationship to the classical terminal web of other epithelial tissues. Naive adult Sprague-Dawley rats (n ¼ 28) were utilized. Factin, fodrin, myosin IIA, and CP49 distribution was assessed in anterior and posterior polar sections. For functional analysis, lenses were cultured with or without cytochalasin-D for 3 hr, then processed for confocal microscopy or assessed by laser scan analysis along sutures. Phalloidin labeling demonstrated a dense mesh of F-actin adjacent to posterior sutural domains to a subcapsular depth of 400 lm. Anterior polar sections revealed a comparable actin structure adjacent to anterior suture branches however, it was not developed in superficial fibers. Fodrin and myosin were localized within the web-like actin apparatus. The data was used to construct a model showing that the cytoskeletal array is located within the blunt, variable-width fiber ends that abut at sutures such that the ''terminal web'' flanks the suture on either side. Treatment with cytochalasin-D resulted in partial disassembly of the ''terminal web'' and perturbed cellular organization. Laser scan analysis revealed that cytochalasin-D treated lenses had significantly greater focal variability than control lenses (P ¼ 0.020). We conclude that cortical fibers of rat lenses contain a bipolar structure that is structurally and compositionally analogous to classical terminal webs. The results indicate that the lens ''terminal web'' functions to stabilize lens fiber ends at sutures thus minimizing structural disorder, which in turn, promotes the establishment and maintenance of lens transparency. Anat Rec, 293:1805Rec, 293: -1815Rec, 293: , 2010. V V C 2010 Wiley-Liss, Inc.

The molecular mechanisms underlying lens fiber elongation

“…The basal tips of lens fibers exhibit actin networks that apparently are involved in stabilizing fiber cell/capsule interactions (Bassnett et al, 1999) which reorganize when the basal tips release from the lens capsule to form the posterior suture (Lu et al, 2008). Finally, the tips of lens fibers participating in lens sutures exhibit focal areas of actin, “the terminal web” which has been proposed to be important for stabilizing suture structure (Al-Ghoul et al, 2010). Thus, the actin cytoskeletal network of the lens reorganizes as lens fibers differentiate from lens epithelial cells, and again as fibers differentiate into their final form.…”

Changes to Zonular Tension Alters the Subcellular Distribution of AQP5 in Regions of Influx and Efflux of Water in the Rat Lens

“… 33 In axial sections, it is possible to visualize the sutures as a line extending from the surface to the core of the lens, but it is difficult to observe the anterior and posterior sutures in the same section as they are offset from each other by 60°. 34 In this study, we have investigated the distribution of the AQPs in anterior (IA) and posterior (IP) influx zones by mapping the subcellular distribution of the three AQPs along the two suture lines that extend from the anterior and posterior poles to the lens core. To facilitate this comparison, we have designated three spatial regions in the outer cortex (IA1; IP1), inner cortex (IA2; IP2), and core (IA3; IP3) from which higher-resolution images have been taken to enable comparison between the labeling obtained from lenses exposed to different degrees of zonular tension ( Fig.…”

Targeted deletion of RIC8A in mouse neural precursor cells interferes with the development of the brain, eyes, and muscles

“…3D, black arrowheads, n 5 5), which are indicative of defects in adhesion and/or migration (Hsu et al, 2006;Shakespeare et al, 2009;Son et al, 2013). Normally, in the lens development, the first primary fibers are surrounded by the forming secondary fibers that start to elongate anteriorly and posteriorly from the equatorial part, and finally surround the primary fibers (Al-Ghoul et al, 2010). After termination of the elongation of lens secondary fibers, their tips attach to one another and form Y-shaped suture in the anterior and a reversed ø-shaped suture in the posterior part of the lens (Al-Ghoul et al, 2010;Son et al, 2013).…”

“…Normally, in the lens development, the first primary fibers are surrounded by the forming secondary fibers that start to elongate anteriorly and posteriorly from the equatorial part, and finally surround the primary fibers (Al-Ghoul et al, 2010). After termination of the elongation of lens secondary fibers, their tips attach to one another and form Y-shaped suture in the anterior and a reversed ø-shaped suture in the posterior part of the lens (Al-Ghoul et al, 2010;Son et al, 2013). To characterize the migration and/or adhesion defects in Nes;Ric8a CKO mutant mice, we analyzed the formation of the anterior suture of the lens using Phalloidin to label the F-actin in the fibers.…”