Background:

The role of calcineurin (protein phosphatase 2B (PP2B)) in the pathogenesis of human dilated cardiomyopathy (DCM) has not been fully elucidated. We determined the potential involvement of calcineurin in the pathogenesis of DCM caused by mutations in CnB1, a subunit of calcineurin.

Methods: By whole-exome sequencing, we identified a new CnB1 variant in a Han Chinese proband with cardiomyopathy from a 3-generation family with 2 normal individuals and 3 individuals with familial dilated cardiomyopathy. The potential pathogenic variant was validated by Sanger sequencing. We performed functional and mechanistic experiments in a CnB1-knockin (KI) mouse model and at the cellular level.

Results: We detected a rare heterozygous CnB1 variant (p.D102A)

in a proband with dilated cardiomyopathy. This variant was localized to the EF hand 3 region of CnB1, where no variants have been previously reported. KI mice harboring the p.D102A variant exhibited decreased cardiac function and cardiac dilatation. Immunoblotting, RT-PCR and immunofluorescence results showed decreased cardiomyocyte size and heart failure-related protein expression. A calcineurin activity assay demonstrated decreased calcineurin activity in the KI mice, accompanied by the decreased ability of CnB1 to bind CnA.

Conclusions: CnB1 p.D102A is a disease-associated variant

that confers susceptibility to cardiac dilatation. This variant is associated with impaired calcineurin activity and a subsequent decrease in the ability of CnB1 to bind CnA.

背景：

钙调神经磷酸酶（蛋白磷酸酶 2B (PP2B)）在人扩张型心肌病 (DCM) 发病机制中的作用尚未完全阐明。我们确定了钙调神经磷酸酶在由 CnB1（钙调神经磷酸酶的一个亚基）突变引起的 DCM 发病机制中的潜在参与。

方法：通过全外显子组测序，我们在一名患有心肌病的汉族先证者中发现了一个新的 CnB1 变异，该先证者来自 3 代家族，其中包括 2 个正常个体和 3 个家族性扩张型心肌病个体。通过 Sanger 测序验证了潜在的致病变异。我们在 CnB1-knockin (KI) 小鼠模型和细胞水平上进行了功能和机械实验。

结果：我们检测到一种罕见的杂合CnB1变异 (p.D102A)

在患有扩张型心肌病的先证者中。该变体定位于CnB1的 EF 手 3 区域，以前没有报道过该区域的变体。携带 p.D102A 变体的 KI 小鼠表现出心脏功能下降和心脏扩张。免疫印迹、RT-PCR 和免疫荧光结果显示心肌细胞大小和心力衰竭相关蛋白表达减少。钙调神经磷酸酶活性测定表明 KI 小鼠的钙调神经磷酸酶活性降低，同时 CnB1 结合 CnA 的能力降低。

结论： CnB1 p.D102A 是一种疾病相关变异

这赋予对心脏扩张的易感性。该变体与钙调神经磷酸酶活性受损以及随后 CnB1 结合 CnA 的能力降低有关。