Human iPSC-derived neurons reveal early developmental alteration of neurite outgrowth in the late-occurring neurodegenerative Wolfram syndrome

Depletion of WFS1 compromises mitochondrial function in hiPSC-derived neuronal models of Wolfram syndrome

“…To study mitochondrial function in clinically relevant WS cellular platforms, we generated NSCs and neurons from previously established hiPSC lines derived from three WS patients (WS1, WS2, WS5) along with two healthy individuals as controls (CT1, CT2) ( Boissart et al., 2013 ; Pourtoy-Brasselet et al., 2021 ; Shang et al., 2014 ) ( Figure S1 A). Cellular identities of hiPSC-derived cells were confirmed by immunofluorescence and gene expression analyses of cell-specific markers, such as NESTIN and PAX6 for NSCs, and TUJ1, MAP2, and NeuN for neurons ( Figures 1 A, 1B, and S1 B–S1D).…”

“…Cellular identities of hiPSC-derived cells were confirmed by immunofluorescence and gene expression analyses of cell-specific markers, such as NESTIN and PAX6 for NSCs, and TUJ1, MAP2, and NeuN for neurons ( Figures 1 A, 1B, and S1 B–S1D). Our neuronal differentiation method generated neurons of cortical nature ( Pourtoy-Brasselet et al., 2021 ), as evident from the gene expression of POU3F2 , CUX1 , and TBR1 that are specific for cortical neurons and by TBR1 immunostaining in TUJ1 + neurons ( Figures S1 E and S1F). Since disease-associated mutations in WFS1 cause the protein to be unstable and degraded by the proteasome ( Guo et al., 2011 ), WFS1 was detected only in control NSCs and neurons but not in WS cells ( Figures 1 B–1D).…”

“…In order to study the implication of mitochondria in WS pathogenesis, we established a list of 382 mitochondria-associated genes and compared the expression of these genes in three CT (control) and three WS hiPSC-derived NSCs and neurons using our previously published RNA-seq datasets ( Pourtoy-Brasselet et al., 2021 ). Among 881 and 944 differentially expressed genes (DEGs) identified in WS compared with CT respectively in NSCs and neurons, a number of mitochondria-associated DEGs were found in WS NSCs and neurons (p value ≤ 5%; fold change ≥ 1.5; minimum reads > 100) ( Figures 1 E and 1F).…”

A deep phenotyping study in mouse and iPSC models to understand the role of oligodendroglia in optic neuropathy in Wolfram syndrome

“…This may reflect the phenotypic heterogeneity of the more than 200 mutations of the WFS1 gene that have been described as causing the disease [50] and suggests that future studies should include several mutant cell lines/models. However, a comprehensive set of in vitro studies showed that these rather limited transcriptional changes do not translate into a MAM phenotype, as has been described for mutant WFS1 iPSC-derived neurons [54, 75]. Specifically, the ER-mitochondria interactions, as measured with a proximity assay, were similar between mutant and isogenic oligodendroglia, and this was associated with normal ER Ca 2+ storage, no increased ER stress susceptibility, normal mitochondrial activity and normal phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol levels.…”

“…In recent years, efforts to improve our knowledge on the neuronal phenotype of Wolfram patients and Wfs1 animal models ensued. In neurons, WFS1 deficiency has been associated with MAM dysregulation, impaired neurite outgrowth and synapse formation, and increased cytosolic Ca 2+ concentration [54, 75]. A recent study using brain organoids showed that this abnormal synapse formation and function goes hand in hand with decreased expression of the excitatory amino acid transporter 2 (EAAT2) and compromised glutamate clearance in astrocytes [73].…”