Abstract：
Noonan syndrome patients harboring causative variants in LZTR1 are particularly at risk to develop severe and early-onset hypertrophic cardiomyopathy. In this study, we investigate the mechanistic consequences of a homozygous variant LZTR1L580P by using patient-specific and CRISPR-Cas9-corrected induced pluripotent stem cell (iPSC) cardiomyocytes. Molecular, cellular, and functional phenotyping in combination with in silico prediction identify an LZTR1L580P-specific disease mechanism provoking cardiac hypertrophy. The variant is predicted to alter the binding affinity of the dimerization domains facilitating the formation of linear LZTR1 polymers. LZTR1 complex dysfunction results in the accumulation of RAS GTPases, thereby provoking global pathological changes of the proteomic landscape ultimately leading to cellular hypertrophy. Furthermore, our data show that cardiomyocyte-specific MRAS degradation is mediated by LZTR1 via non-proteasomal pathways, whereas RIT1 degradation is mediated by both LZTR1-dependent and LZTR1-independent pathways. Uni- or biallelic genetic correction of the LZTR1L580P missense variant rescues the molecular and cellular disease phenotype, providing proof of concept for CRISPR-based therapies.
摘要：
在LZTR1中具有致病变异的Noonan综合征患者尤其有发展为严重和早发性肥厚型心肌病的风险。在这项研究中,我们通过使用患者特异性和CRISPR-Cas9校正的诱导多能干细胞(iPSC)心肌细胞,研究了纯合变体LZTR1L580P的机制后果.分子,细胞，功能表型与计算机预测相结合，可确定引起心脏肥大的LZTR1L580P特异性疾病机制。预测变体改变二聚化结构域的结合亲和力,促进线性LZTR1聚合物的形成。LZTR1复杂功能障碍导致RASGTPases的积累，从而引起蛋白质组景观的整体病理变化，最终导致细胞肥大。此外，我们的数据表明，心肌细胞特异性MRAS降解是由LZTR1通过非蛋白酶体途径介导的，而RIT1降解是由LZTR1依赖性和LZTR1非依赖性途径介导的。LZTR1L580P错义变异的单等位基因或双等位基因基因校正挽救了分子和细胞疾病表型，为基于CRISPR的疗法提供概念证明。
