Tracking Mesenchyme Primordial Cells with Gli1 Labeled the Optic Nerve Head and Periocular Mesenchyme

Abstract

Purpose : The periocular mesenchyme (POM) cells contribute to the development of the ciliary body, trabecular meshwork and the iridocorneal angle. It is known that cells expressing the Sonic hedgehog (Shh) signaling pathway play a key role in anterior eye development. This pathway is mediated by the Gli transcription factors (Gli1, Gli2, and Gli3) that differentially activate and repress the expression of specific eye development genes (Pax6, Pax2 and Vax1). The objective of this project was to determine if Gli1 positive cells contribute to the POM and anterior eye structures by using inducible Gli1-CreERT2; tdTomato^flox mouse model, and thus could serve as a new probe for studying anterior eye development.

Methods : A transgenic mouse for tracking mesenchyme primordial cells using a Gli1-Cre-ERT2;Rosa26-tdTomato^flox construct was bred. The tdtomato fluorescence can be induced at specific developmental stages with tamoxifen and cells tracked. Eyes from mice that were induced on post-natal day 3 or 7, and sacrificed on day P10 were examined with confocal microscopy on frozen sections and whole mounts to determine the spatial distribution of the cells derived from Gli1+ progenitors.

Results : In Gli1-CreERT2; tdTomato^flox mice induced on P3 or P7, the POM and optic head were both labeled when evaluated at P10. In contrast, the cornea and sclera did not show any positive cells.

Conclusions : This new inducible Gli1-CreERT2; tdTomato^flox mouse model appears to be an excellent system for determining the role of periocular mesenchyme in anterior eye development. The elegance of this model is it can be activated at specific developmental stages and Gli1+ cells derivatives can be tracked and other detection probes (EDU, GFPCol1, calcein, nuclear stains, etc), can be incorporated to determine cell division, collagen expression, bone deposition and over all tissue structure. Our initial results suggest that POM cell may be contributing to the development of the anterior angle chamber that forms between P4-P10.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Eye section from mouse treated with tamoxifen on P7 and sacrificed on P10. The Gli1 positive cells (red) are in the mesenchyme area. Nuclei in other eye structures are labeled with DAPI (green). The lens was displaced in processing.