Abstract
Purpose :
Sall family transcription factor contains Sall1-4, and we had previously reported that Sall3 plays essential roles in hirozontal cell maturation. We also found that Sall1 was expressed in microglia in both retina and brain, and plays pivotal roles for maturation of microglia. During the work, we had found that Sall1 was also expressed in developing lens strongly and asked its roles for lens development.
Methods :
Knock-in mouse harboring EGFP in Sall1 locus (Sall1-gfp) was used for analyses of Sall1 expression pattern and phenotype of loss of function of Sall1. Since Sall1 knockout mice dies immediate after the birth, lens specific knockout mouse of Sall1 was generated by using Sall1-flox/flox and Pax6-lens-cre mice. Lens development was examined by immunostaining and electron microscopic approaches using sectioned Sall1-knockout lens. The microarray was performed to analyze molecular signature of the lens of Sall1-knockout.
Results :
Expression of Sall1, which was examined by EGFP expression of Sall1-gfp mouse lens, was observed in whole lens at E13.5, then, the expression was started to be down regulated from lens epithelium and remained in fiber cells from E14.5. After birth, EGFP signals were observed in the equator region, and disappeared during lens fiber internalization. Lens morphogenesis of Sall1-knockout mice was severely perturbed, which was first observed at around E14. Small vacuoles were in the center of lens fibers region, and it became more prominent at E15. Enucleation did not occur, and Pax6 remained to be expressed in nucleus after birth. Electron microscopic analysis indicated that the vacuoles were not in the inside of fiber cells, instead, cell-cell contact was disturbed and detached. However, gap junction structure was observed in periphery, and immunostaining of ZO1, beta-catenin, N-cadherin showed rather appropriate expression pattern in Sall1-knockout lens, suggesting that expression of cell adhesion machinery proteins was not affected. Finally, microarray analysis showed down-regulation of some of cytoskeletal genes in Sall1-knockout lens.
Conclusions :
Sall1 is straongly expressed in lens from early developmental stage and plays essential roles for fiber cell maturation probably through regulation of expression levels of cytoskeletal genes. Taken our previous works together, we revealed that Sall family members play pivotal roles for maturation process of various cell lineages in the eye.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.