Abstract
Huntington’s disease (HD) is an inherited neurodegenerative disorder caused by a CAG repeat expansion in the huntingtin gene (HTT). Disease progression is characterized by the loss of vulnerable neuronal populations within the striatum. A consistent phenotype across HD models is disruption of nucleocytoplasmic transport and nuclear pore complex (NPC) function. Here we demonstrate that high content imaging is a suitable method for detecting mislocalization of lamin-B1, RAN and RANGAP1 in striatal neuronal cultures thus allowing a robust, unbiased, highly powered approach to assay nuclear pore deficits. Furthermore, nuclear pore deficits extended to the selectively vulnerable DARPP32 + subpopulation neurons, but not to astrocytes. Striatal neuron cultures are further affected by changes in gene and protein expression of RAN, RANGAP1 and lamin-B1. Lowering total HTT using HTT-targeted anti-sense oligonucleotides partially restored gene expression, as well as subtly reducing mislocalization of proteins involved in nucleocytoplasmic transport. This suggests that mislocalization of RAN, RANGAP1 and lamin-B1 cannot be normalized by simply reducing expression of CAG-expanded HTT in the absence of healthy HTT protein.
Highlights
Huntington’s disease (HD) is a progressive, invariably fatal neurodegenerative disorder characterized by choreic movements, psychomotor decline, dementia and psychiatric symptoms (Ross and Tabrizi, 2011; Tabrizi et al, 2020)
Recent research has provided evidence that nuclear pore complex (NPC) function is disrupted in normal aging and dysfunction may contribute to neuronal loss in several neurodegenerative diseases, including frontotemporal dementia (FTD), amyotrophic lateral sclerosis (ALS), Parkinson’s disease (PD) and HD (Patel and Chu, 2011; Zhang et al, 2015; Grima et al, 2017; Chou et al, 2018)
In order to reduce such variability, we used iPSC lines obtained from an unaffected mother and her HD affected family and differentiated these to striatal neurons, alongside lines of an isogenic ESC series (IsoHD, with lengths of 30Q, 45Q, and 81Q) (Ooi et al, 2019)
Summary
Huntington’s disease (HD) is a progressive, invariably fatal neurodegenerative disorder characterized by choreic movements, psychomotor decline, dementia and psychiatric symptoms (Ross and Tabrizi, 2011; Tabrizi et al, 2020). It is caused by a CAG repeat expansion in exon 1 of the huntingtin (HTT) gene, which in unaffected individuals contains thirty five or fewer CAGs, whereas individuals carrying forty CAGs or more are certain to develop the disease (Andrew et al, 1993). Despite ubiquitous expression of the mutant huntingtin protein (mHTT) and accumulation of aggregates (Davies et al, 1997; DiFiglia et al, 2016), the reasons for the early and selective loss of these neuronal subpopulations and the precise mechanisms by which mHTT causes neurodegeneration remain relatively unknown. Recent research has provided evidence that nuclear pore complex (NPC) function is disrupted in normal aging and dysfunction may contribute to neuronal loss in several neurodegenerative diseases, including frontotemporal dementia (FTD), amyotrophic lateral sclerosis (ALS), Parkinson’s disease (PD) and HD (Patel and Chu, 2011; Zhang et al, 2015; Grima et al, 2017; Chou et al, 2018)
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