Abstract
Purpose :
Vertebrate lenses transmit light and focus images onto the retina of the eye. A functional lens needs to be formed in an optically correct shape. The greater portion of the lens is comprised of highly elongated lens fibre cells that are aligned concentrically around the optical axis. This highly ordered alignment develops during collective migration of lens fibre cells from the lens equator to the poles. Using rodent models, we have shown that apical cell junctions, extensions of lamellipodia at the basal tips, planar cell polarity (PCP) signalling, and Wnt/Frizzled interaction cooperatively regulate fibre cell migration. However, all these findings came from observations of fixed-samples. Accordingly, vital in vivo information is necessary to further understand fibre movement.
Methods :
Using a zebrafish live-imaging system, we are currently analysing lens fibre cell movement in vivo. Each lens fibre cell was colour-barcoded using the Zebrabow multi-fluorescent protein expression system. Embryos were mounted at 2 or 3 days post-fertilisation and lens development was live-imaged using upright, inverted or lightsheet confocal microscopes.
Results :
Strips of lens fibre cells coming from the lens equator aligned radially around the anterior pole. At the anterior pole, the fibre apical tips formed an umbilical (point) suture. Time-lapse recordings spanning 18 hours detected migration of the fibre apical tips toward the anterior pole. The migrating apical tips showed broad and irregular morphology, and then changed into tapered ends when they reached the anterior pole.
Conclusions :
We are trying to answer the following questions: 1) Do lens fibre tips migrate directly to the poles, or do they follow some other prescribed route? 2) Do they move at a constant speed all the way from the equator to the poles, or do they move at variable rates, depending on the lens zones? 3) Do lens fibre cells maintain the same positions relative to neighbouring cells, or do they undergo cellular rearrangement (such as convergent and extension movement)? Live-imaging data will validate our previous findings and will uncover 4D dynamics of lens fibre cell movement.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.