Gene-Agnostic Gene Therapy to Preserve Vision

No, we have not.

We have found cones that live even until one year in the dorsal region of the rd1, rd10, and rho KO mice. We also have seen a loss of the cone ERG as early as P21. We have studied both of these phenotypes and have published on them. The survival of cones in the dorsal periphery is due to retinoic acid production by Mueller glia in that region (Amamoto et al. eLife, 2022). The loss of the cone ERG, even though almost all cones are still present, looks like it is due to too much retinal (Xue et al. PNAS 2024).

I don’t know, it will depend on getting the protein into the mitochondria. I understand it is hard to get genes into the mitochondria. I believe people have been able to get some correction for LHON, which is also a mitochondrial disease, so perhaps it would work.

I don’t know, it will depend on getting the protein into the mitochondria. I understand it is hard to get genes into the mitochondria. I believe people have been able to get some correction for LHON, which is also a mitochondrial disease, so perhaps it would work.

It might be due to more light-induced damage due to bisretinoids. Janet Sparrow has published her ideas on this topic and her model makes good sense.

We have two. One is typically used, induction of oxidative damage due to delivery of an oxidizing chemical, sodium iodate. The RPE is very sensitive to this chemical. The other one is a genetic approach, using a gene that induces oxidative damage to turn on the damage in a specific cell type using mouse genetics. We can then control the pace and level of oxidative damage using a D-amino acid in the drinking water.

That is a good question. I don’t know the answer!

Our therapies would be aimed at a time when cone vision starts to go down, but there are still lots of cones left to save.

The expense of running a clinical trial. It is hundreds of millions of dollars to run a trial. There are lots of good ideas to try out, but not many companies can afford to make bets on most of them.

I don’t know of a capsid that targets rods vs cones. One can use a rod or cone promoter for that, but most of them are not specific to only rods or only cones. We inject before all of the cones get sick, so at P0. It takes the AAV up to 3 weeks to maximally express so we want to get the therapeutic gene in the cones before they die.

There are quite a few clinical trials and for most of them, we don’t yet know the results.

I think that those approaches are too late. If a cell has already launched a program to kill itself, even if you save it, it might not be functional.

Yes.

Good questions, Enrica Strettoi and others have looked at synaptic rearrangements when rods die in RP mouse models. I don’t know of work on Mueller glia other than they do upregulate GFAP and have some other changes in morphology. I would hope that if cones live longer that some of these effects would be muted.

Our model is dependent upon D-amino acid addition. It can cause degeneration even in young animals. We see non-autonomous effects, i.e. cone and rod degeneration when only the RPE expresses DAAO. In the Nrf2 KO, aged animals have some histological changes suggestive of AMD, ie basal infoldings change. I don’t know of any effects on rod and cone survival.

A negative result in the OCT or ERG might simply indicate that the construct or transgenic strategy is not working. We have looked at levels of ROS and seen them. We also have the hyper sensor that tells us where there is ROS. It seems that, even though we see ROS and hyper in blood vessels when we express it there, meaning the construct is working, that we don’t see leaking or dying vessels. Not sure why, but it seems that there is a threshold for different cell types in terms of their ability to deal with ROS.

Absolutely. I am told that the FDA does not like the idea of multiple genes, but I suspect that is incorrect. There is now a trial going on with 3 of the Yamanaka factors for ganglion cell rejuvenation.

I don’t think so. We added glucose transporter and it had no effect. Jose Sahel has a rescue of cones with Rdcvf, a factor that helps cones take up more glucose. When we give cones the ability to make their own glucose, we get cone rescue.

That would be worth doing but we have not done that.

No. Among mammals, only some primates have a fovea.

Yes, they do.

Yes, we see no staining of rods. RNA expression also shows its cone specific.

Yes, we have three treatments that do that. Check out papers by Sean Wang from my lab.