The role of SLC7A13/AGT1-variation in human cystinuria

SLC7A13/AGT1 变异在人类胱氨酸尿症中的作用

• 批准号: 496611648
• 负责人: Professor Dr. Jan Halbritter
• 金额: --
• 依托单位: Medizinische Klinik mit Schwerpunkt Nephrologie (CCM)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/496611648?language=en
• 关键词: role; SLC7A13; AGT1; variation; human

Cystinuria (CU) is an inherited kidney stone disorder with significant morbidity due to frequent recurrence and associated chronic kidney disease. Mechanistically, disturbed tubular cystine reabsorption based on the dysfunctional heterodimeric amino acid transporter rBAT/SLC3A1-BAT1/SLC7A9 leads to urinary cystine precipitation and consecutive calculus formation. While biallelic pathogenic variants of either SLC3A1 or SLC7A9 can be found in the majority of cases, no clear genotype-phenotype correlation could be established until today. Additionally, in about 10-15% of patients, genetic diagnostics are inconclusive, as none or only monoallelic variants can be identified and dominant inheritance is discussed controversially. Recently, the existence of a second heterodimeric cystine transporter consisting out of the heavy chain rBAT/SLC3A1 with the novel light chain partner AGT1/SLC7A13 has been demonstrated in S3 segments from murine tubular membranes. In a pilot-study with 132 CU-patients, we identified three AGT1-missense variants (N45K, L270F, M452T) on top of biallelic known SLC3A1 or SLC7A9 mutations. In preliminary in vitro analyses, we demonstrated a negative impact of identified SLC7A13/AGT1 patient variants on rBAT N-glycosylation, membrane expression, and subsequent cystine uptake. We therefore hypothesize that specific SLC7A13/AGT1-variants will have an impact on disease severity in human cystinuria, either by genetic modification or full penetrance. With this application, we propose the following four specific aims: i) identification and functional validation of both rare and common SLC7A13/AGT1-variants in combination with patient-specific rBAT and BAT1-variations in a cohort of 400 CU-patients recruited from the multinational EUROCYS-registry and additional major collaborators in the field, ii) evaluation of the prevalence and impact of the common SLC7A13/AGT1 variant N45K in larger CU-cohorts, iii) assessment of epigenetic modification of SLC7A13/AGT1, SLC7A9, and SLC3A1 as determinants of intra- and inter-familial disease variability in CU, and iv) application of a genotype-first approach in order to characterize human SLC7A13/AGT1-associated phenotypes in an unbiased manner via large Exome-datasets (> 200,000 samples from the UK-biobank and Geisinger-database). By successful implementation of aforementioned aims, we believe to clarify the clinical significance of SLC7A13/AGT1-germline variation and to eventually provide long-missing phenotype-genotype correlations in human CU. Unraveling the mechanisms of disturbed luminal complex expression of the AGT1-rBAT and BAT1-rBAT transporters may further pave the way for novel pharmacological treatment options supporting complex stabilization and plasma membrane abundance.

胱氨酸尿症(Cystinuria，CU)是一种遗传性肾结石疾病，因其频繁复发和伴发慢性肾脏疾病而发病率显著。基于功能失调的异二聚体氨基酸转运体rBAT/SLC3A1-BAT1/SLC7A9的肾小管胱氨酸重吸收障碍从机制上导致尿胱氨酸沉淀和结石的形成。虽然在大多数病例中可以发现SLC3A1或SLC7A9的双等位致病变异，但直到今天才能确定明确的基因型-表型相关性。此外，在大约10%-15%的患者中，遗传诊断是不确定的，因为没有或只有单等位基因变异可以被识别，显性遗传是有争议的讨论。最近，在小鼠肾小管膜的S3片段中发现了由重链rBAT/SLC3A1和新的轻链伙伴AGT1/SLC7A13组成的第二个异二聚体胱氨酸转运体。在一项针对132名CU患者的先导性研究中，我们在已知双等位基因SLC3A1或SLC7A9突变的基础上发现了三个AGT1错义变异(N45K、L270F、M452T)。在初步的体外分析中，我们证明了已识别的SLC7A13/AGT1患者变异对rBAT N-糖基化、膜表达和随后的胱氨酸摄取产生了负面影响。因此，我们假设，特定的SLC7A13/AGT1变异将通过基因修饰或完全外显性对人类胱氨酸尿症的疾病严重性产生影响。通过这项应用，我们提出了以下四个具体目标：i)鉴定罕见和常见的SLC7A13/AGT1变异体，结合患者特有的rBAT和BAT1变异体，在400名CU患者的队列中，从多国EUROCys注册中心和该领域的其他主要合作者招募，ii)评估共同的SLC7A13/AGT1变异体N45K在更大的CU队列中的患病率和影响，iii)评估SLC7A13/AGT1、SLC7A9和SLC3A1的表观遗传修饰作为CU家族内和家族间疾病变异性的决定因素以及iv)应用基因优先的方法，以无偏见的方式通过大的Exome数据集(&gt；来自英国生物库和盖辛格数据库的20万个样本)。通过上述目标的成功实现，我们相信将阐明SLC7A13/AGT1-生殖系变异的临床意义，并最终提供人类慢性萎缩性胃炎长期缺失的表型-基因型相关性。解开AGT1-rBAT和BAT1-rBAT转运体管腔复合体表达紊乱的机制，可能进一步为支持复合体稳定和质膜丰度的新的药物治疗方案铺平道路。