Presentation Information
[II-TKIS-OR-1]Combined Contribution of SORBS2 and RBM20 for Atrial Septal Defect and Restrictive Cardiomyopathy
○Reika Sakurai1,2, Masaya Kunimatsu3, Keiko Uchida2,4, Tadashi Inoue2, Yuichiro Miyaoka5, Hiroyuki Yamagishi2,6 (1.Keio University School of Medicine, Tokyo, Japan, 2.The Department of Pediatrics, Keio University School of Medicine, Tokyo, Japan, 3.The Department of Pediatrics, Graduate School of Medicine, Chiba University, Chiba, Japan, 4.The Department of Physiology, Tokyo Medical University, Tokyo, Japan, 5.Regenerative Medicine Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan, 6.Tokyo Metropolitan Children's Medical Center, Tokyo, Japan)
Keywords:
Restrictive cardiomyopathy,Whole exome sequencing,Oligogenic inheritance
Background: Restrictive cardiomyopathy (RCM) has poor prognosis, characterized by persistent diastolic heart failure regardless of wall thickness or systolic function. We identified a family where a 2-year-old girl presented with both RCM and atrial septal defect (ASD), while her father and younger sister had only ASD. This suggests an oligogenic background involving genetic modifiers. We focused on SORBS2 (a Z-line protein) and RBM20 (a titin splicing regulator) to investigate mechanisms from morphological defects to restrictive physiology.
Methods: Whole exome sequencing of family members identified variants; we validated SORBS2 (p.D391N) and RBM20 (p.R518C): 1) Assessing intracellular localization and aggregation of mutant SORBS2 in HEK293T cells. 2) Quantifying splicing activity via TTN minigene reporter (Exons 241-243) and Bioanalyzer. 3) Establishing iPSC lines with both variants using CRISPR-Cas9.
Results: The father and younger sister carried a heterozygous SORBS2 variant, the healthy mother carried an RBM20 variant, and the proband was double-heterozygous. Variant SORBS2 showed abnormal intracellular aggregates, suggesting compromised Z-line structural integrity. In the minigene assay, RBM20 R518C reduced TTN splicing 0.58-fold to normal. Functional analysis of iPSC lines with variants differentiated into cardiomyocytes are underway.
Conclusion: Combined Z-line failure and titin splicing dysfunction may contribute to RCM. Since SORBS2 is an RBM20 target, these variants likely synergistically exacerbate RCM, in addition to ASD, in the proband of this familial case.
Methods: Whole exome sequencing of family members identified variants; we validated SORBS2 (p.D391N) and RBM20 (p.R518C): 1) Assessing intracellular localization and aggregation of mutant SORBS2 in HEK293T cells. 2) Quantifying splicing activity via TTN minigene reporter (Exons 241-243) and Bioanalyzer. 3) Establishing iPSC lines with both variants using CRISPR-Cas9.
Results: The father and younger sister carried a heterozygous SORBS2 variant, the healthy mother carried an RBM20 variant, and the proband was double-heterozygous. Variant SORBS2 showed abnormal intracellular aggregates, suggesting compromised Z-line structural integrity. In the minigene assay, RBM20 R518C reduced TTN splicing 0.58-fold to normal. Functional analysis of iPSC lines with variants differentiated into cardiomyocytes are underway.
Conclusion: Combined Z-line failure and titin splicing dysfunction may contribute to RCM. Since SORBS2 is an RBM20 target, these variants likely synergistically exacerbate RCM, in addition to ASD, in the proband of this familial case.