RUNX1 Upregulation Causes Mitochondrial Dysfunction via Regulating the PI3K-Akt Pathway in iPSC from Patients with Down Syndrome

Abstract

Down syndrome (DS) is the most common autosomal aneuploidy caused by trisomy of chromosome 21. Previous studies demonstrated that DS affected mitochondrial functions, which may be associated with the abnormal development of the nervous system in patients with DS. Runt-related transcription factor 1 (RUNX1) is an encoding gene located on chromosome 21. It has been reported that RUNX1 may affect cell apoptosis via the mitochondrial pathway. The present study investigated whether RUNX1 plays a critical role in mitochondrial dysfunction in DS and explored the mechanism by which RUNX1 affects mitochondrial functions. Expression of RUNX1 was detected in induced pluripotent stem cells of patients with DS (DS-iPSCs) and normal iPSCs (N-iPSCs), and the mitochondrial functions were investigated in the current study. Subsequently, RUNX1 was overexpressed in N-iPSCs and inhibited in DS-iPSCs. The mitochondrial functions were investigated thoroughly, including reactive oxygen species levels, mitochondrial membrane potential, ATP content and lysosomal activity. Finally, RNA-sequencing was used to explore the global expression pattern. It was observed that the expression levels of RUNX1 in DS-iPSCs were significantly higher than those in normal controls. Impaired mitochondrial functions were observed in DS-iPSCs. Of note, overexpression of RUNX1 in N-iPSCs resulted in mitochondrial dysfunction, while inhibition of RUNX1 expression could improve the mitochondrial function in DS-iPSCs. Global gene expression analysis indicated that overexpression of RUNX1 may promote the induction of apoptosis in DS-iPSCs by activating the PI3K/Akt signaling pathway. The present findings indicate that abnormal expression of RUNX1 may play a critical role in mitochondrial dysfunction in DS-iPSCs.

Realizing the potential of exploiting human IPSCs and their derivatives in research of Down syndrome

“…These observations provide evidence for impaired mitochondrial function in DS iPSCs, which is consistent with the observations in DS cells (Qiu et al, 2017). An RNA-seq study revealed there was significantly increased expression of RUNX1 in DS iPSCs compared to normal controls (Liu et al, 2023). Overexpression of RUNX1 in control iPSCs resulted in mitochondrial dysfunction, whereas depletion of RCAN1 or inhibition of RUNX1 expression improved mitochondrial function in DS iPSCs (Liu et al, 2023;Parra et al, 2018).…”

“…The expression of RUNX1 gene on Chr 21 was found to be higher in DS iPSCs compared to normal controls, which resulted in mitochondrial dysfunction in DS iPSCs via promoting apoptosis through the activation of the PI3K/Akt signaling pathway (Liu et al, 2023). Therefore, reducing RUNX1 expression could improve mitochondrial function in DS iPSCs.…”

“…An RNA-seq study revealed there was significantly increased expression of RUNX1 in DS iPSCs compared to normal controls (Liu et al, 2023). Overexpression of RUNX1 in control iPSCs resulted in mitochondrial dysfunction, whereas depletion of RCAN1 or inhibition of RUNX1 expression improved mitochondrial function in DS iPSCs (Liu et al, 2023;Parra et al, 2018). Global gene expression analysis indicated the overexpression of RUNX1 could promote the induction of apoptosis in DS iPSCs by activating the PI3K/Akt signaling pathway (Liu et al, 2023).…”

“…Down syndrome (DS) is a genetic condition caused by either partial or full trisomy of human chromosome 21 (HSA21), which leads to delayed brain development, intellectual disability, and premature Alzheimer's disease (AD) (Esposito et al, 2008;Liu et al, 2023;Ma et al, 2021;Ponroy Bally et al, 2020). Individuals with DS also have smaller whole brain volume (Giffin-Rao et al, 2022;Huo et al, 2018), specifically, they have reduced numbers of calretinin-expressing interneurons in the cortex (Giffin-Rao et al, 2022).…”

Brief guide to RNA sequencing analysis for nonexperts in bioinformatics

“…Advances in next-generation sequencing technologies for RNA sequencing (RNA-seq) revolutionized the research field of transcriptome analysis. In addition, breakthroughs in computational approaches and ample deposits of RNA-seq data allow researchers to expand analyzing transcriptomes of interest in addition to performing bench experiments ( Kim et al, 2022 , Liu et al, 2023 ). However, variations and diversities of analysis protocols and tools, and the lack of knowledge in optimized workflow make it difficult for transcriptome analysis ( Conesa et al, 2016 ).…”