In Vivo Analysis of Troponin C Knock-In (A8V) Mice Evidence that TNNC1 Is a Hypertrophic Cardiomyopathy Susceptibility Gene
In Vivo Analysis of Troponin C Knock-In (A8V) Mice Evidence that TNNC1 Is a Hypertrophic Cardiomyopathy Susceptibility Gene
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DOI：
10.1161/circgenetics.114.000957
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发表时间：
2015-10-01
影响因子：
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通讯作者：
Pinto, Jose R.
中科院分区：
文献类型：
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作者：
Martins, Adriano S.;Parvatiyar, Michelle S.;Pinto, Jose R.
研究背景：细丝蛋白的突变与肥厚型心肌病有关，但尚未证实TNNC 1（编码肌钙蛋白C的基因）中鉴定的变异体可引起体内心脏重塑。方法和结果TNNC 1-A8 V先证者在34岁时被诊断为严重梗阻性肥厚型心肌病，表现为左、右心室壁轻度至中度增厚，左心室尺寸减小，左心房增大和高动力左心室收缩功能。通过超声心动图和压力-容积研究对含有A8 V突变的基因工程敲入（KI）小鼠（杂合子=KI-TnC-A8 V（+/-）;纯合子=KI-TnC-A8 V（+/+））进行了表征。三个月大的KI-TnC-A8 V（+/+）小鼠表现出心室尺寸减小、轻度舒张功能障碍和增强的收缩功能，而KI-TnC-A8 V（+/-）小鼠在14个月大时表现出心脏限制。KI心脏表现出心房增大、乳头肌肥大和纤维化。使用液相色谱-质谱法测定突变型心肌肌钙蛋白C（约21%）掺入KI-TnC-A8 V（+/-）心肌肌丝。在完整的KI-TnC-A8 V（+/-）和KI-TnC-A8 V（+/+）心肌细胞中记录到舒张期肌节长度减少、缩短增加、Ca 2+和收缩瞬变延长。皮肤纤维收缩的Ca 2+敏感性随突变基因剂量增加而增加：KI-TnC-A8 V（+/+）>KI-TnC-A8 V（+/-）>野生型，而KI-TnC-A8 V（+/+）对重氮-2的光解弛豫更慢。结论TNNC 1-A8 V突变体增加了细纤维的Ca 2+结合亲和力，导致Ca 2+稳态和细胞重构的改变。导致心脏舒张功能障碍这些体内改变进一步暗示了TNNC 1突变在心肌病发展中的作用。
Background Mutations in thin-filament proteins have been linked to hypertrophic cardiomyopathy, but it has never been demonstrated that variants identified in the TNNC1 (gene encoding troponin C) can evoke cardiac remodeling in vivo. The goal of this study was to determine whether TNNC1 can be categorized as an hypertrophic cardiomyopathy susceptibility gene, such that a mouse model can recapitulate the clinical presentation of the proband.Methods and Results The TNNC1-A8V proband diagnosed with severe obstructive hypertrophic cardiomyopathy at 34 years of age exhibited mild-to-moderate thickening in left and right ventricular walls, decreased left ventricular dimensions, left atrial enlargement, and hyperdynamic left ventricular systolic function. Genetically engineered knock-in (KI) mice containing the A8V mutation (heterozygote=KI-TnC-A8V(+/-); homozygote=KI-TnC-A8V(+/+)) were characterized by echocardiography and pressure-volume studies. Three-month-old KI-TnC-A8V(+/+) mice displayed decreased ventricular dimensions, mild diastolic dysfunction, and enhanced systolic function, whereas KI-TnC-A8V(+/-) mice displayed cardiac restriction at 14 months of age. KI hearts exhibited atrial enlargement, papillary muscle hypertrophy, and fibrosis. Liquid chromatography-mass spectroscopy was used to determine incorporation of mutant cardiac troponin C (approximate to 21%) into the KI-TnC-A8V(+/-) cardiac myofilament. Reduced diastolic sarcomeric length, increased shortening, and prolonged Ca2+ and contractile transients were recorded in intact KI-TnC-A8V(+/-) and KI-TnC-A8V(+/+) cardiomyocytes. Ca2+ sensitivity of contraction in skinned fibers increased with mutant gene dose: KI-TnC-A8V(+/+)>KI-TnC-A8V(+/-)>wild-type, whereas KI-TnC-A8V(+/+) relaxed more slowly on flash photolysis of diazo-2.Conclusions The TNNC1-A8V mutant increases the Ca2+-binding affinity of the thin filament and elicits changes in Ca2+ homeostasis and cellular remodeling, which leads to diastolic dysfunction. These in vivo alterations further implicate the role of TNNC1 mutations in the development of cardiomyopathy.