I536T variant of RBM20 affects splicing of cardiac structural proteins that are causative for developing dilated cardiomyopathy

RBM20 is one of the genes predisposing to dilated cardiomyopathy (DCM). Variants in the RS domain have been reported in many DCM patients, but the pathogenicity of variants within the RNA-recognition motif remains unknown. Two human patients with the I536T-RBM20 variant without an apparent DCM phenotype were identified in sudden death cohorts. A splicing reporter assay was performed, and an I538T knock-in mouse model (Rbm20(I538T)) was generated to determine the significance of this variant. The reporter assay demonstrated that the human I536T variant affected the TTN splicing pattern compared to wild-type. In the mouse experiments, Rbm20(I538T) mice showed different splicing patterns in Ttn, Ldb3, Camk2d, and Ryr2. The expressions of Casq1, Mybpc2, and Myot were upregulated in Rbm20(I538T) mice, but Rbm20(I538T) mice showed neither DCM nor cardiac dysfunction on histopathological examination and ultrasound echocardiography. The I536T-RBM20 (I538T-Rbm20) variant changes gene splicing and affects gene expression, but the splicing and expression changes in Ttn and Ca handling genes such as Casq1, Camk2d, and Ryr2 do not cause DCM morphology in the mouse model. Key messages center dot Two human patients with the I536T-RBM20 variant without a DCM phenotype were identified. center dot A splicing reporter assay demonstrated that the variant affected the TTN splicing. center dot Rbm20(I538T) mice showed neither DCM nor cardiac dysfunction. center dot Rbm20(I538T) mice showed different splicing patterns and the gene expressions.

Automated summary

This study identified the manifestation of I536T-RBM20 variant in human patients and its effects in a mouse model. The variant alters gene splicing and affects gene expression, but does not cause dilated cardiomyopathy.