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A human pluripotent stem cell model to study the haploinsufficiency and dominant negative molecular mechanisms of Marfan Syndrome

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Author(s):
Juliana Santana Borsoi
Total Authors: 1
Document type: Doctoral Thesis
Press: São Paulo.
Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
Defense date:
Examining board members:
Lygia da Veiga Pereira; Luciana Amaral Haddad; Alexandre da Costa Pereira; Salmo Raskin
Advisor: Lygia da Veiga Pereira; Luis Ernesto Farinha Arcieri
Abstract

The FBN1 gene encodes the extracellular matrix (ECM) protein fibrillin-1, the major structural component of the microfibrils that form the elastic fibers. Mutations in this gene were related to the occurrence of Marfan Syndrome (MFS), a pleiotropic autosomal dominant connective tissue disorder whose clinical manifestations affect the cardiovascular, skeletal and ocular systems. Although more than 3,000 pathogenic variants in FBN1 have been described, there are no well-established genotype-phenotype correlations for the syndrome, with few exceptions, and two molecular mechanisms have been proposed and validated to explain its development: haploinsufficiency (HI - i.e. the lack of the regular amount of wild-type fibrillin-1) and dominant-negativity (DN - i.e. the disturbance of the ECM by an incorporated aberrant protein), and differences between groups of patients classified as HI or DN have been reported. Because patients have different genetic backgrounds and gene modifiers may play a role in the pathogenesis of the syndrome, the specific consequences of each group of mutations are not clear. To overcome these issues, we have successfully edited a hiPSC line from a healthy donor using CRISPR/Cas9 to generate isogenic HI and DN mutants for FBN1. We showed that the predicted HI mutations lead to mRNA decay and no protein production and that the DN variant result in the secretion of an aberrant fibrillin-1, as expected. Although we did not observe any distinct phenotypes when we compared hiPSC-derived cardiomyocytes from the different groups, possibly due to their immaturity, we can now take advantage of the plasticity of these stem cell lines to better understand the pathogenesis of Marfan Syndrome in different cell types (AU)

FAPESP's process: 16/16076-4 - Functional analysis of FBN1 mutations in human Pluripotent Stem-Cells (hPSCs)
Grantee:Juliana Borsoi Sant'Ana
Support type: Scholarships in Brazil - Doctorate (Direct)