Lens sutures as morphogen sinks for positional gradient information in pattern formation.

Abstract

Abstract: : Purpose: To propose a morphogenic gradient model for pattern formation by rabbit lens fibres. Methods: Radial fibre elongation was calculated with a computational model with embedded heterochrony (Kwok and Coroneo 2000). Spatial trajectories were mapped for lens fibres in the rabbit lens at 1 and 8 wk development. The zonular radius r of quasi–linear elongation was determined for lens diam of 2R = 2.4 mm (1 wk) and 5.4 mm (8 wk). Results: Spatial trajectories were linear for r/R > 0.3 ± 0.06 at 1 wk increasing to r/R > 0.7 ± 0.14 at 8 wk. The corresponding radial distance of quasi–linear elongation from the equator was 0.84 ± 0.17 mm and 0.81 ± 0.16 mm for 1 and 8 wk respectively. Patterning completion and suture formation were confirmed. Gradient shapes followed suture size. Fibre widths were spatially correlated (P < 0.05). Conclusions: The invariance of the quasi–linear growth field suggests long–range signalling from the equatorial region is preserved between 1–8 wk development. The simulations also indicate that suture formation and fibre curvature may result from complex multi–step interactions between heterochronous fibre elongation and centrifugal diffusion of morphogens. The sutures could act as physical depots that maintain concentration gradients of morphogens. Positional information and antero–posterior patterning in the vertebrate lens may arise from gradients in morphogens or their inhibitors.

Keywords: cataract • anatomy • comparative anatomy