Cellular Models: HD Patient-Derived Pluripotent Stem Cells

Abstract

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by expanded polyglutamine (polyQ)-encoding repeats in the Huntingtin (HTT) gene. Traditionally, HD cellular models consisted of either patient cells not affected by disease or rodent neurons expressing expanded polyQ repeats in HTT. As these models can be limited in their disease manifestation or proper genetic context, respectively, human HD pluripotent stem cells (PSCs) are currently under investigation as a way to model disease in patient-derived neurons and other neural cell types. This chapter reviews embryonic stem cell (ESC) and induced pluripotent stem cell (iPSC) models of disease, including published differentiation paradigms for neurons and their associated phenotypes, as well as current challenges to the field such as validation of the PSCs and PSC-derived cells. Highlighted are potential future technical advances to HD PSC modeling, including transdifferentiation, complex in vitro multiorgan/system reconstruction, and personalized medicine. Using a human HD patient model of the central nervous system, hopefully one day researchers can tease out the consequences of mutant HTT (mHTT) expression on specific cell types within the brain in order to identify and test novel therapies for disease.

Phase Transition of Huntingtin: Factors and Pathological Relevance

“…Studies so far were carried out in vitro , in yeast cells and in HEK cells. It is critical to confirm the current findings in more relevant HD cell models such as neuronal cell lines or iPSC-derived neurons ( Geater et al, 2018 ). Cell-type-specific difference of mHtt aggregation has been reported in mice HD models ( Jansen et al, 2017 ).…”

An RNA-targeting CRISPR–Cas13d system alleviates disease-related phenotypes in Huntington’s disease models

“…Although not age-or sex-matched to our lines from patients with HD, the control samples (controls 1-3) used to evaluate the effects of different lengths of CAG expansions on human neurons have been characterized in previous publications [32][33][34] and checked for aberrant genomic HTT 5,6 . Besides the toxicity of the mutated HTT protein, an increasing body of evidence indicates that mutant HTT mRNA also contributes to disease pathogenesis 7,8 .…”

Recent Overview of the Use of iPSCs Huntington’s Disease Modeling and Therapy

“…Generally, differentiation protocols are based on recapitulating the developmental steps during ontogenesis. The first step in differentiation is neural induction, including the differentiation of iPSCs into NSCs/NPCs, through embryoid bodies (EBs) and neural rosette formation, which is achieved by inhibiting the bone morphogenic protein (BMP) and transforming growth factor beta (TGF-β) pathways to prevent mesodermal and endodermal differentiation [15]. A comprehensive overview of these protocols can be found in our previous work [16].…”

“…Furthermore, HD-iPSC-NPCs can organize into three-dimensional (3D) organoids mimicking the architecture of brain tissue. In addition, iPSC-derived HD models represent a much more suitable alternative for drug screening and toxicity testing than widely used animal models [15,32]. Table 2.…”