👤 Kai Kaarniranta

Juvenile neuronal ceroid lipofuscinosis (JNCL) is a rare neurodegenerative disorder caused by mutations in the CLN3 gene and characterized by early vision loss and a progressive neurological decline. To characterize the progression of retinal pathology, we conducted a 15-month study using the Cln3Δex7/8 mouse model which carries the most common causative mutation of JNCL. Retinal function was assessed every three months from the age of 3-15 months using electroretinography (ERG), optical coherence tomography (OCT), fundus imaging, and immunohistochemistry. OCT and fundus imaging in the Cln3Δex7/8 mice revealed a progressive thinning of the inner nuclear layer (INL) and an accumulation of subretinal drusenoid deposits. We detected a progressive loss of rod bipolar cells (RBCs) with immunofluorescence staining which was accompanied by ubiquitin-positive punctae, indicative of a potential role of the ubiquitin-proteasome system (UPS) in the selective loss of RBCs and the associated inner retinal dysfunction. Furthermore, late-stage immune cell activity was observed in the subretinal space of the Cln3Δex7/8 mice. ERG measurements confirmed previous findings of a predominant inner retinal dysfunction and revealed also a more pronounced photoreceptor impairment, as well as an earlier onset of retinal dysfunction than previously reported. These findings provide new insights into the pathological features of retinal degeneration in Cln3Δex7/8 mice, including subretinal drusenoid deposits, tubular subretinal fluid, and ubiquitin accumulation as well as a better overview of the rate of the degeneration process, thus expanding our understanding of JNCL pathogenesis. Show less

The accumulation of amyloid-β-containing neuritic plaques and intracellular tau protein tangles are key histopathological hallmarks of Alzheimer's disease (AD). This type of pathology clearly indicates that the mechanisms of neuronal housekeeping and protein quality control are compromised in AD. There is mounting evidence that the autophagosome-lysosomal degradation is impaired, which could disturb the processing of APP and provoke AD pathology. Beclin 1 is a molecular platform assembling an interactome with stimulating and suppressive components which regulate the initiation of the autophagosome formation. Recent studies have indicated that the expression Beclin 1 is reduced in AD brain. Moreover, the deficiency of Beclin 1 in cultured neurons and transgenic mice provokes the deposition of amyloid-β peptides whereas its overexpression reduces the accumulation of amyloid-β. There are several potential mechanisms, which could inhibit the function of Beclin 1 interactome and thus impair autophagy and promote AD pathology. The mechanisms include (i) reduction of Beclin 1 expression or its increased proteolytic cleavage by caspases, (ii) sequestration of Beclin 1 to non-functional locations, such as tau tangles, (iii) formation of inhibitory complexes between Beclin 1 and antiapoptotic Bcl-2 proteins or inflammasomes, (iv) interaction of Beclin 1 with inhibitory neurovirulent proteins, e.g. herpex simplex ICP34.5, or (v) inhibition of the Beclin 1/Vps34 complex through the activation of CDK1 and CDK5. We will shortly introduce the function of Beclin 1 interactome in autophagy and phagocytosis, review the recent evidence indicating that Beclin 1 regulates autophagy and APP processing in AD, and finally examine the potential mechanisms through which Beclin 1 dysfunction could be involved in the pathogenesis of AD. Show less