Noncompaction of the ventricular myocardium (NVM), the third most diagnosed cardiomyopathy, is characterized by prominent trabeculae and intratrabecular recesses. However, the genetic etiology of 40–60% of NVM cases remains unknown. We identified two infants with NVM, in a nonconsanguineous family, with a typical clinical presentation of persistent bradycardia since the prenatal period. A homozygous missense variant (R223L) of RCAN family member 3 (RCAN3) was detected in both infants using whole-exome sequencing. In the zebrafish model, marked cardiac dysfunction was detected in rcan3 deficiency (MO-rcan3^ATG-injected) and rcan^−/− embryos. Developmental dysplasia of both endocardial and myocardial layers was also detected in rcan3-deficient embryos. RCAN3 R223L variant mRNAs did not rescue heart defects caused by rcan3 knockdown or knockout; however, hRCAN3 mRNA rescued these phenotypes. RNA-seq experiments showed that several genes involved in cardiomyopathies were significantly regulated through multiple signaling pathways in the rcan3-knockdown zebrafish model. In human cardiomyocytes, RCAN3 deficiency resulted in reduced proliferation and increased apoptosis, together with an abnormal mitochondrial ultrastructure. Thus, we suggest that RCAN3 is a susceptibility gene for cardiomyopathies, especially NVM and that the R223L mutation is a potential loss-of-function variant.

心室心肌致密化不全（NVM）是第三大诊断最多的心肌病，其特征是突出的小梁和小梁内隐窝。然而，40-60% NVM 病例的遗传病因仍不清楚。我们在非近亲结婚家庭中发现了两名患有 NVM 的婴儿，其典型临床表现是自产前以来持续性心动过缓。使用全外显子组测序在两名婴儿中检测到RCAN 家族成员 3 ( RCAN3 )的纯合错义变异 (R223L) 。在斑马鱼模型中，在rcan3缺陷（注射 MO- rcan3 ^ATG）和rcan ^−/−胚胎中检测到明显的心脏功能障碍。在rcan3缺陷的胚胎中也检测到心内膜和心肌层的发育不良。RCAN3 R223L 变异 mRNA 不能挽救rcan3敲低或敲除引起的心脏缺陷；然而，hRCAN3 mRNA 挽救了这些表型。RNA-seq 实验表明，在rcan3敲除斑马鱼模型中，多个与心肌病相关的基因通过多种信号通路受到显着调节。在人类心肌细胞中，RCAN3缺陷导致增殖减少、细胞凋亡增加，以及线粒体超微结构异常。因此，我们认为RCAN3是心肌病（尤其是 NVM）的易感基因，并且 R223L 突变是潜在的功能丧失变异。