Reduced PLP1 expression in induced pluripotent stem cells derived from a Pelizaeus–Merzbacher disease patient with a partial PLP1 duplication

Abstract

Pelizaeus-Merzbacher disease (PMD) is an X-linked recessive disorder characterized by dysmyelination of the central nervous system (CNS). We identified a rare partial duplication of the proteolipid protein 1 gene (PLP1) in a patient with PMD. To assess the underlying effect of this duplication, we examined PLP1 expression in induced pluripotent stem (iPS) cells generated from the patient's fibroblasts. Disease-specific iPS cells were generated from skin fibroblasts obtained from the indicated PMD patient and two other PMD patients having a 637-kb chromosomal duplication including entire PLP1 and a novel missense mutation (W212C) of PLP1, by transfections of OCT3/4, C-MYC, KLF4 and SOX2 using retro-virus vectors. PLP1 expressions in the generated iPS cells were examined by northern blot analysis. Although PLP1 expression was confirmed in iPS cells generated from two patients with the entire PLP1 duplication and the missense mutation of PLP1, iPS cells generated from the patient with the partial PLP1 duplication manifesting a milder form of PMD showed null expression. This indicated that the underlying effect of the partial PLP1 duplication identified in this study was different from other PLP1 alterations including a typical duplication and a missense mutation.

Modeling the Mutational and Phenotypic Landscapes of Pelizaeus-Merzbacher Disease with Human iPSC-Derived Oligodendrocytes

“…We characterized hiPSCs, OPCs, and oligodendrocytes from 12 individuals with PMD and identified shared and individual defects spanning PLP1 expression, PLP1 splicing, OPC production, oligodendrocyte morphology, and response to small-molecule therapeutics. Although PLP1 is restricted to the oligodendrocyte lineage, DM20 mRNA is robustly transcribed in pluripotent cells, 60 providing an opportunity for rapid assessment of mutation-specific transcript defects in a scalable, homogeneous population of cells. DM20, the OPC-specific isoform of PLP1 and the sole isoform expressed in hiPSCs, limited our ability to interpret the effects of mutations in the PLP1-specific region of exon 3b.…”

“…However, although the protein is not translated, DM20 mRNA is robustly transcribed in pluripotent stem cells. 60 Serendipitously, this provides an opportunity for rapid assessment of specific transcript defects without the protracted differentiation of oligodendrocytes. To begin to characterize the effects of mutations in our panel, we used our RNA-seq dataset to interrogate DM20 mRNA expression and splicing directly in hESCs and hiPSCs ( Figure 2A).…”

Involvement of ER Stress in Dysmyelination of Pelizaeus-Merzbacher Disease with PLP1 Missense Mutations Shown by iPSC-Derived Oligodendrocytes

“…In addition, those previous results were obtained through analyses using nonhuman models, non-patient-derived cells, or nonoligodendrocyte models, and it is unknown whether the results obtained in those models are applicable to human patients. Although the establishment of iPSCs from a PMD patient with partial duplication of PLP1 gene has been reported, those iPSCs were not differentiated into oligodendrocytes for disease modeling (Shimojima et al., 2012). Thus, in the present study, we focused on the pathologic effects of PLP1 missense mutations and established patient-specific iPSCs from two PMD patients with different mutation sites and different levels of clinical severity.…”

Patient-derived iPS cells for unveiling the molecular pathology of Pelizaeus-Merzbacher disease: a commentary on ‘Reduced PLP1 expression in induced pluripotent stem cells derived from a Pelizaeus–Merzbacher disease patient with a partial PLP1 duplication’

“…1 They established iPS cells from three patients with PelizaeusMerzbacher disease (PMD), which is an X-linked disorder of the CNS. PMD is caused by mutations of the PLP1 gene, which is predominantly expressed by oligodendrocytes, but is barely or faintly detectable in the lymphocytes or fibroblasts.…”

“…Rare null mutations such as deletion or prematurely terminating mutations may cause spastic paraplegia accompanied by mild neuropathy. Undifferentiated iPS cells can be used in the PLP1 gene expression study, as demonstrated by Shimojima et al 1 Meanwhile, differentiation into oligodendrocyte lineage is required for studies in molecular mechanisms and drug screening for the treatments. molecular outcome of the genomic rearrangement.…”