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Functional characterization of an Alzheimer disease‐associated deletion in SORL1
Author(s) -
Dykxhoorn Derek M.,
Simon Shaina A.,
Kunkle Brian W.,
Cuccaro Michael L.,
Vance Jeffery M.,
Cukier Holly N.,
PericakVance Margaret A.
Publication year - 2020
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1002/alz.045888
Subject(s) - biology , induced pluripotent stem cell , alzheimer's disease , microglia , psen1 , microbiology and biotechnology , amyloid precursor protein , neuroscience , genetics , gene , embryonic stem cell , pathology , immunology , disease , medicine , inflammation
Background Over 20 genetic loci have been consistently associated with Alzheimer disease (AD) with accumulating evidence pointing to alterations of the endolysosomal pathway as playing key roles. The sortilin‐related receptor 1 ( SORL1 ) gene has been associated with AD through multiple genetic studies and has been suggested to function by guiding APP to the endocytic pathway. We recently identified a family with multiple AD affected individuals that bear a single base pair deletion (g.4292delG) predicted to result in a frameshift alteration and early termination of the protein (p.Cys143Ser*1). Previous studies have implicated SORL1 variants in AD pathogenesis, but it remains unclear how this deletion impacts SORL1 protein function and AD development. Method Induced pluripotent stem cells (iPSC) lines were developed to examine the cellular and molecular consequences in neuronal and glial cell (astrocytes and microglia) populations, which can otherwise only be collected postmortem. Each iPSC line generated was validated for pluripotency through immunocytochemical staining and shown to be negative for any large‐scale chromosomal abnormalities via karyotyping. The patient iPSC lines and control lines were differentiated into cortical neurons and glia cells for functional analyses, including amyloid beta production and uptake, vesicular trafficking, and neurite outgrowth. Result We have generated iPSC lines from two individuals bearing this deletion in SORL1 and have confirmed their pluripotency by immunocytochemistry. These cells were differentiated into cortical neurons whose identity was confirmed by staining for forebrain markers. The SORL1 variant bearing cortical neurons showed enlarged endosomes compared to the neurons derived from control iPSCs, as measured by the staining with an anti‐RAB5 antibody and fluorescent microscopy. In addition, the SORL1 deletion bearing neurons showed an upregulation of pathogenic amyloid beta 42 measured by ELISA. Glial cells have emerged as pivotal players in the maintenance of brain homeostasis. Therefore, we will assess the functional impact of this deletion of SORL1 in microglial cells and astrocytes. Conclusion In summary, our results support that the p.Cys143Ser*1 variant is indeed pathogenic. iPSC‐derived neurons and glia cells bearing the deletion in SORL1 p.Cys143Ser*1 variant shows cellular deficits associated with AD pathology which could serve as new avenues for therapeutic development.