Optic cup-specific ablation of Adamts9, encoding a secreted metalloproteinase, leads to anterior segment dysgenesis

Abstract

Purpose : Adamts9 is highly expressed in the anterior pole of the optic cup during eye development, and weakly in the lens, corneal stroma, and hyaloid vasculature. ADAMTS9 is a target of the O-fucosylation pathway enzyme B3GLCT, whose mutations cause Peters-Plus Syndrome (PPS), in which anterior segment dysgenesis (ASD) occurs alongside extraocular defects. Adamts9 haploinsufficiency also causes ASD in mice. However, death of Adamts9 null embryos before eye development prompted us to investigate the full function of this protein in ocular development by conditional Adamts9 ablation in the eye.

Methods : We generated mice with conditional Adamts9 ablation in the optic cup, neural crest, or endothelial cells, using α-Cre, Wnt1-Cre, and Tie2-Cre strains crossed with Adamts9 floxed mice (Adamts9^fl). Eyes were analyzed at birth (Wnt1-Cre), or 21 days (a-Cre, Tie2-Cre) using stereomicroscopy, histochemistry, and immunofluorescence and compared to eyes from age-matched Adamts9^fl/fl or Cre+ littermates. A dual fluorescent reporter strain (mG/mT) was used to ascertain the deletion domain of each Cre-driver.

Results : Although Wnt1-Cre and Tie2-Cre mediated deletion of Adamts9 did not lead to consistent eye anomalies, all Adamts9^fl/fl; α-Cre mice had corneal opacity and microphthalmia. Histology revealed ASD, microphakia, and lens extrusion through the lens capsule in Adamts9^fl/fl; α-Cre and Adamts9^fl/+; α-Cre eyes. These anomalies were previously seen in Adamts9^+/- eyes. α-Cre deleted a fluorescence reporter in the prospective retina of mG/mT/+; α-Cre mice.

Conclusions : These studies suggest that 1. ADAMTS9 secreted by the optic cup acts in trans on anterior segment development, providing potential insights on mechanisms of PPS 2. ADAMTS9 produced by neural crest cells or vascular endothelial cells does not contribute substantially to eye development 3. ADAMTS9 could be a candidate gene for ASD in humans.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

Adamts9^fl/fl; α-Cre eyes have corneal opacity, shallow anterior chamber (AC), and lens extrusions shown by stereomicroscopy (top) and H&E staining (center). An iridocorneal adhesion (arrow) within a shallow AC and posterior lens extrusions (arrowheads) are evident in an Adamts9^fl/fl; α-Cre eye. Bottom: Fluorescent microscopy of a mG/mT/+; α-Cre eye, indicating the deletion domain of α-Cre (green). L=lens, R=retina. Scale bar: 500µm.