Reduced number and caliber of optic nerve axons and smaller optic nerves in mice homozygous for a glaucoma-causing mutation in Adamts10

Abstract

Purpose : Previously, we identified a Gly661Arg variant of A Disintegrin and Metalloproteinase with ThromboSpondin motifs-10 (ADAMTS10) as the disease-causing variant in a dog model of primary open angle glaucoma with elevated intraocular pressure (IOP). ADAMTS10 is essential for formation of fibrillin-1 microfibrils, which are key components of the extracellular matrix. Mutations in ADAMTS10 also cause Weill-Marchesani syndrome, characterized by short stature and lens dislocations. We have also found that adamts10 plays an essential role in development of retinal ganglion cells in zebrafish. Here, we generated mice carrying the Gly661Arg mutation of Adamts10 using CRISPR-Cas9 to test if they develop glaucoma phenotypes.

Methods : Adamts10^G661A/G661A and wild type control (wt) mice at 6 and 24 months of age were used. Diurnal and nocturnal IOP was measured with TonoLab. Anterior chamber depth was determined by spectral domain optical coherence tomography. Optic nerves were fixed then treated with osmium tetroxide, embedded in epon and cross-sectioned. Images of PPD-stained nerve sections were acquired and nerve areas, axon numbers and axon areas determined using ImageJ.

Results : Although IOP was not affected by the Gly661Arg mutation, Adamts10^G661A/G661A mice were shorter and had lower body weights compared to wt. Adamts10^G661A/G661A mice had 5% shallower anterior chambers (6m, p = 0.001; 24m, p = 0.01), suggestive of lens dislocation anteriorly. Adamts10^G661A/G661A mice had lower axon counts at both 6 and 24 months of age (p = 0.0006 and 0.008, respectively), while smaller optic nerves (13%, p = 0.0001) and smaller caliber of optic nerve axons (3%, p = 0.002) were found at 24 months of age.

Conclusions : Unlike dogs homozygous for the Gly661Arg mutation, IOP was not changed in Adamts10^G661A/G661A mice. However, Adamts10^G661A/G661A mice had smaller bodies and possible dislocated lenses, consistent with Weill-Marchesani syndrome. Fewer axon numbers found in Adamts10^G661A/G661A mice at early age is possibly consistent with a role for Adamts10 in retinal ganglion cell development. Converse to our previous findings in mice mutations in the fibrillin-1 gene (Fbn1), Adamts10^G661A/G661A mice had smaller optic nerves and smaller caliber of optic nerve axons, suggesting opposing effects of mutations in Fbn1 and Adamts10.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.