Abstract：
BACKGROUND: Steroid-resistant nephrotic syndrome is the second leading cause of chronic kidney disease among patients < 25 years of age. Through exome sequencing, identification of > 65 monogenic causes has revealed insights into disease mechanisms of nephrotic syndrome (NS).
METHODS: To elucidate novel monogenic causes of NS, we combined homozygosity mapping with exome sequencing in a worldwide cohort of 1649 pediatric patients with NS.
RESULTS: We identified homozygous missense variants in MYO1C in two unrelated children with NS (c.292C > T, p.R98W; c.2273 A > T, p.K758M). We evaluated publicly available kidney single-cell RNA sequencing datasets and found MYO1C to be predominantly expressed in podocytes. We then performed structural modeling for the identified variants in PyMol using aligned shared regions from two available partial structures of MYO1C (4byf and 4r8g). In both structures, calmodulin, a common regulator of myosin activity, is shown to bind to the IQ motif. At both residue sites (K758; R98), there are ion-ion interactions stabilizing intradomain and ligand interactions: R98 binds to nearby D220 within the myosin motor domain and K758 binds to E14 on a calmodulin molecule. Variants of these charged residues to non-charged amino acids could ablate these ionic interactions, weakening protein structure and function establishing the impact of these variants.
CONCLUSIONS: We here identified recessive variants in MYO1C as a potential novel cause of NS in children.
METHODS: To elucidate novel monogenic causes of NS, we combined homozygosity mapping with exome sequencing in a worldwide cohort of 1649 pediatric patients with NS.
RESULTS: We identified homozygous missense variants in MYO1C in two unrelated children with NS (c.292C > T, p.R98W; c.2273 A > T, p.K758M). We evaluated publicly available kidney single-cell RNA sequencing datasets and found MYO1C to be predominantly expressed in podocytes. We then performed structural modeling for the identified variants in PyMol using aligned shared regions from two available partial structures of MYO1C (4byf and 4r8g). In both structures, calmodulin, a common regulator of myosin activity, is shown to bind to the IQ motif. At both residue sites (K758; R98), there are ion-ion interactions stabilizing intradomain and ligand interactions: R98 binds to nearby D220 within the myosin motor domain and K758 binds to E14 on a calmodulin molecule. Variants of these charged residues to non-charged amino acids could ablate these ionic interactions, weakening protein structure and function establishing the impact of these variants.
CONCLUSIONS: We here identified recessive variants in MYO1C as a potential novel cause of NS in children.
摘要：
背景：类固醇耐药型肾病综合征是25岁以下患者慢性肾病的第二大病因。通过外显子组测序,对>65种单基因病因的鉴定揭示了对肾病综合征（NS）疾病机制的见解。
方法：为了阐明NS的新的单基因原因，我们将纯合性图谱与外显子组测序相结合,纳入了1649例NS患儿的全球队列.
结果：我们在两个无关的NS儿童中鉴定了MYO1C中的纯合错义变异（c.292C>T，p.R98W;c.2273A>T,p.K758M)。我们评估了公开的肾脏单细胞RNA测序数据集，发现MYO1C主要在足细胞中表达。然后,我们使用来自MY01C的两个可用部分结构(4byf和4r8g)的比对共享区域对PyMol中鉴定的变体进行结构建模。在这两种结构中，钙调素,一种常见的肌球蛋白活性调节剂，显示与IQ基序结合。在两个残基位点（K758；R98），有离子-离子相互作用稳定内粒和配体相互作用：R98与肌球蛋白运动域内附近的D220结合，K758与钙调蛋白分子上的E14结合。这些带电残基到不带电氨基酸的变体可以消除这些离子相互作用，削弱蛋白质结构和功能，建立这些变体的影响。
结论：我们在此确定MYO1C中的隐性变异是儿童NS的潜在新原因。
方法：为了阐明NS的新的单基因原因，我们将纯合性图谱与外显子组测序相结合,纳入了1649例NS患儿的全球队列.
结果：我们在两个无关的NS儿童中鉴定了MYO1C中的纯合错义变异（c.292C>T，p.R98W;c.2273A>T,p.K758M)。我们评估了公开的肾脏单细胞RNA测序数据集，发现MYO1C主要在足细胞中表达。然后,我们使用来自MY01C的两个可用部分结构(4byf和4r8g)的比对共享区域对PyMol中鉴定的变体进行结构建模。在这两种结构中，钙调素,一种常见的肌球蛋白活性调节剂，显示与IQ基序结合。在两个残基位点（K758；R98），有离子-离子相互作用稳定内粒和配体相互作用：R98与肌球蛋白运动域内附近的D220结合，K758与钙调蛋白分子上的E14结合。这些带电残基到不带电氨基酸的变体可以消除这些离子相互作用，削弱蛋白质结构和功能，建立这些变体的影响。
结论：我们在此确定MYO1C中的隐性变异是儿童NS的潜在新原因。
