Eupatilin improves cilia defects in human CEP290 ciliopathy models.

The photoreceptor outer segment is a highly specialized primary cilium essential for phototransduction and vision. Biallelic pathogenic variants in the cilia-associated gene CEP290 cause non-syndromic Leber congenital amaurosis 10 (LCA10) and syndromic diseases, where the retina is also affected. While RNA antisense oligonucleotides and gene editing are potential treatment options for the common deep intronic variant c.2991+1655A>G in CEP290 , there is a need for variant-independent approaches that could be applied to a broader spectrum of ciliopathies. Here, we generated several distinct human models of CEP290 -related retinal disease and investigated the effects of the flavonoid eupatilin as a potential treatment. Eupatilin improved cilium formation and length in CEP290 LCA10 patient-derived fibroblasts, in gene-edited CEP290 knockout (CEP290 KO) RPE1 cells, and in both CEP290 LCA10 and CEP290 KO iPSCs-derived retinal organoids. Furthermore, eupatilin reduced rhodopsin retention in the outer nuclear layer of CEP290 LCA10 retinal organoids. Eupatilin altered gene transcription in retinal organoids, by modulating the expression of rhodopsin, and by targeting cilia and synaptic plasticity pathways. This work sheds light into the mechanism of action of eupatilin, and supports its potential as a variant-independent approach for CEP290 -associated ciliopathies.

The heat-shock response co-inducer arimoclomol protects against retinal degeneration in rhodopsin retinitis pigmentosa.

Retinitis pigmentosa (RP) is a group of inherited diseases that cause blindness due to the progressive death of rod and cone photoreceptors in the retina. There are currently no effective treatments for RP. Inherited mutations in rhodopsin, the light-sensing protein of rod photoreceptor cells, are the most common cause of autosomal-dominant RP. The majority of mutations in rhodopsin, including the common P23H substitution, lead to protein misfolding, which is a feature in many neurodegenerative disorders. Previous studies have shown that upregulating molecular chaperone expression can delay disease progression in models of neurodegeneration. Here, we have explored the potential of the heat-shock protein co-inducer arimoclomol to ameliorate rhodopsin RP. In a cell model of P23H rod opsin RP, arimoclomol reduced P23H rod opsin aggregation and improved viability of mutant rhodopsin-expressing cells. In P23H rhodopsin transgenic rat models, pharmacological potentiation of the stress response with arimoclomol improved electroretinogram responses and prolonged photoreceptor survival, as assessed by measuring outer nuclear layer thickness in the retina. Furthermore, treated animal retinae showed improved photoreceptor outer segment structure and reduced rhodopsin aggregation compared with vehicle-treated controls. The heat-shock response (HSR) was activated in P23H retinae, and this was enhanced with arimoclomol treatment. Furthermore, the unfolded protein response (UPR), which is induced in P23H transgenic rats, was also enhanced in the retinae of arimoclomol-treated animals, suggesting that arimoclomol can potentiate the UPR as well as the HSR. These data suggest that pharmacological enhancement of cellular stress responses may be a potential treatment for rhodopsin RP and that arimoclomol could benefit diseases where ER stress is a factor.

Increase in presynaptic territory of C-terminals on lumbar motoneurons of G93A SOD1 mice during disease progression.

Compensatory synaptic plasticity is reported in muscle and the central nervous system of motor neuron disease patients, and transgenic SOD1 mice, but direct ultrastructural evidence for spinal motoneurons is lacking. Prompted by our observation in spinal cords from autopsied patients suggesting selective enlargement of the ultrastructurally distinctive C-type terminal synapsing with spinal motoneurons, we examined the ultrastructural synaptology of lumbar motoneurons during disease progression in age- and sex-matched wild-type mice, transgenic G93A SOD1 mice, and mice overexpressing normal human SOD1 (Wt(SOD1)). Prescribed criteria classified presynaptic terminals of motoneurons into five ultrastructural classes (S, F, T, M, and C). Computerized morphometry on electronmicrographs was used to measure their appositional lengths, coverage of the motoneuron membrane, and sizes of postsynaptic structures. No terminal degeneration occurred in wild-type or Wt(SOD1) mice. In transgenic mice, degeneration of motoneurons and S-terminals and F-terminals commenced presymptomatically (10 weeks), and continued into the symptomatic stage (18 weeks). However, C-terminals were preserved. Morphometry confirmed significant reductions in frequency and membrane coverage for S-terminals and F-terminals between 10 and 18 weeks, but a maintained frequency of C-terminals coupled with increased appositional length and coverage of the motoneuron membrane. Increased C-terminal size was matched by growth of its characterizing postsynaptic cistern and Nissl body. The results reveal selective preservation and increased presynaptic territory of the C-type terminal. As C-terminals derive from cholinergic intrasegmental propriospinal interneurons and may modulate motoneuron excitability, their increased presynaptic territory on surviving motoneurons of transgenic SOD1 mice may represent a means of maintaining excitability, compensating for the loss of overall presynaptic input.