Distinct sub-cellular autophagy impairments occur independently of protein aggregation in induced neurons from patients with Huntington’s disease

Abstract

Huntington's disease (HD) is a neurodegenerative disorder caused by CAG expansions in the huntingtin (HTT) gene. Modelling HD has remained challenging, as rodent and cellular models poorly recapitulate the disease. To address this, we generated induced neurons (iNs) through direct reprogramming of human skin fibroblasts, which retain age-dependent epigenetic characteristics. HD-iNs displayed profound deficits in autophagy, characterised by reduced transport of late autophagic structures from the neurites to the soma. The neurite-specific alterations in autophagy resulted in shorter, thinner and fewer neurites presented by HD-iNs. CRISPRi-mediated silencing of HTT did not rescue this phenotype but rather resulted in additional autophagy alterations in ctrl-iNs, highlighting the importance of wild type HTT in neuronal autophagy. In summary, our work identifies a distinct subcellular autophagy impairment in aged patient derived HD-neurons and provides a new rational for future development of autophagy activation therapies.

Warburg-like metabolic transformation underlies neuronal degeneration in sporadic Alzheimer’s disease

“…To gain a more complete understanding of potential ADassociated transcriptomic and metabolic alterations in neurons, we generated directly converted induced neurons (iNs) from patient-derived fibroblasts by the overexpression of Ascl1:2A:Ngn2 (Mertens et al, 2015). Importantly, iNs maintain the aging signatures of their donors (Huh et al, 2016;Kim et al, 2018;Mertens et al, 2015) and are a unique model system to assess agerelated disease phenotypes in live human neurons (Jovi ci c et al, 2015;Pircs et al, 2021;Victor et al, 2018).…”

Chemical Replacement of Noggin with Dorsomorphin Homolog 1 for Cost-Effective Direct Neuronal Conversion

“…Our finding will be helpful to facilitate future cohort-based studies using iN technology, which is particularly useful for better understanding aspects of human neuronal cell aging (Huh et al, 2016 ; Mertens et al, 2015 ) and human age-related diseases such as ALS (Jovıˇcić et al, 2015 ), Huntington's disease (Pircs et al, 2021 ; Victor et al, 2018 ), Parkinson's disease (Drouin-Ouellet et al, 2021 ), or Alzheimer's disease (Ma et al, 2020 ; Mertens et al, 2021 ).…”

“…Comparative iN-based disease modeling studies are based on relatively large cohorts of patient FBs, and demand several rounds of efficient and reliable conversion efficiencies into iNs with mature neuronal properties. Despite the use of LDN-193189 and other ALK inhibitors, many such studies that have assessed large FB cohorts critically depend on recombinant Noggin, which, however, is variable and expensive (Drouin-Ouellet et al, 2021 ; Mertens et al, 2021 ; Pircs et al, 2021 ).…”

Induced pluripotent stem cell-derived and directly reprogrammed neurons to study neurodegenerative diseases: The impact of aging signatures

“…Another age-associated hallmark in HD is the increase in epigenetic aging rates, which was previously described in post-mortem brain tissues (Steve Horvath et al, 2016). Since directly converted neurons from HD patients retain the age of donor cell (Pircs et al, 2022), this factor was investigated in this neuronal model. Pircs and colleagues examined the epigenetic age and confirmed a significantly increased DNA methylation predicted biological age in neurons induced from HD patients with respect to the control neurons (Pircs et al, 2022).…”

“…Aging hallmarks represent important contributors to neurodegeneration development and each aging feature differentially interacts with genetic and environmental factors in disease progression and manifestation. Also, its effect is related to the subtype-specific cell type/neuron (Kim et al, 2018;Victor et al, 2018;Pircs et al, 2022), underpinning the distinct involvement of aging in different NDDs. The relevance of age for late-onset NDDs development has been pictorially illustrated in Figure 3.…”