Human iPSC-derived Down syndrome astrocytes display genome-wide perturbations in gene expression, an altered adhesion profile, and increased cellular dynamics

Abstract

Down syndrome (DS), caused by the triplication of human chromosome 21, leads to significant alterations in brain development and is a major genetic cause of intellectual disability. While much is known about changes to neurons in DS, the effects of trisomy 21 on non-neuronal cells such as astrocytes are poorly understood. Astrocytes are critical for brain development and function, and their alteration may contribute to DS pathophysiology. To better understand the impact of trisomy 21 on astrocytes, we performed RNA-sequencing on astrocytes from newly produced DS human induced pluripotent stem cells (hiPSCs). While chromosome 21 genes were upregulated in DS astrocytes, we found consistent up- and down-regulation of genes across the genome with a strong dysregulation of neurodevelopmental, cell adhesion and extracellular matrix molecules. ATAC (assay for transposase-accessible chromatin)-seq also revealed a global alteration in chromatin state in DS astrocytes, showing modified chromatin accessibility at promoters of cell adhesion and extracellular matrix genes. Along with these transcriptomic and epigenomic changes, DS astrocytes displayed perturbations in cell size and cell spreading as well as modifications to cell-cell and cell-substrate recognition/adhesion, and increases in cellular motility and dynamics. Thus, triplication of chromosome 21 is associated with genome-wide transcriptional, epigenomic and functional alterations in astrocytes that may contribute to altered brain development and function in DS.

Clustered Protocadherins Emerge as Novel Susceptibility Loci for Mental Disorders

“…Consequently, expression levels of these isoforms remain high in adult brain tissues, similar to that of the fetal stage, supporting a model of delayed brain maturation in the DS patients (Almenar-Queralt et al, 2019). Moreover, human DS iPSCderived astrocytes show a transcriptional profile between fetal and mature stages, further supporting the delayed maturation model of DS (Ponroy Bally et al, 2020). Furthermore, these DS astrocytes show reduced levels of the Pcdhγ expression and have selective impairments in Pcdhγ-mediated cell adhesion (Ponroy Bally et al, 2020).…”

Modeling Neurodevelopmental and Neuropsychiatric Diseases with Astrocytes Derived from Human-Induced Pluripotent Stem Cells

“…In addition, the expression of synaptic proteins in hiPSC-neurons was reduced when co-cultured with DS hiPSC-astrocytes, supporting the idea that astrocytes contribute to the neuronal deficits in DS [ 129 ]. Gene expression studies of DS hiPSC-astrocytes revealed genome-wide transcriptional alterations, including genes involved in neuronal development and cell adhesion [ 99 , 130 ]. Interestingly, the differential transcriptional expression of cell adhesion-related genes was not observed in hiPSC-NPCs, indicating the emergence of these impairments during astrocytic differentiation [ 130 ].…”

“…Gene expression studies of DS hiPSC-astrocytes revealed genome-wide transcriptional alterations, including genes involved in neuronal development and cell adhesion [ 99 , 130 ]. Interestingly, the differential transcriptional expression of cell adhesion-related genes was not observed in hiPSC-NPCs, indicating the emergence of these impairments during astrocytic differentiation [ 130 ]. The hiPSC-astrocyte model of DS validated astrocytic deficits described in Ts65Dn mice and patient tissues and identified several impairments in astrocyte-neuron interactions, demonstrating the contribution of astrocytes to the altered development and function of DS brain.…”

“…Some of the results from different groups, however, were not consistent with each other. While elevated spontaneous Ca 2+ fluctuations were described in DS hiPSC-astrocytes [ 128 ], a recent study with a larger number of DS hiPSC lines did not observe altered Ca 2+ signaling in hiPSC-astrocytes [ 130 ]. Thus, it is necessary to consider the variability in the hiPSCs and astrocytes used in different labs.…”

Studying Abnormal Chromosomal Diseases Using Patient-Derived Induced Pluripotent Stem Cells

“…Transplanted DS-astroglia also did not promote neural development in the developing brain of immunodeficient mice (Chen et al, 2014 ). DS-astroglia also exhibited abnormal synaptogenesis and neuronal excitability with transcriptomic and epigenetic changes in genes associated with neurodevelopmental, cell adhesion and extracellular matrix functions (Araujo et al, 2018 ; Mizuno et al, 2018 ; Ponroy Bally et al, 2020 ). Together, DS-iPSCs and their differentiated neural derivatives recapitulated various cellular defects that were consistent with various symptoms in DS patients and might enable the discovery of the underlying pathology and the development of treatments for DS.…”