Chen Xinhui, Shi Yihua, Fu Feng, Wang Lebo, Yu Hongying, Yang Dehao, Wang Xinchen, Ying Chenxin, Wang Haoyu, Lin Zhiru, Wang Haotian, Zhang Fan, Zheng Xiaosheng, Guo Yuru, Wang Yaoting, Zeng YiHeng, Zhao Miao, Chen Yiling, Li Jiaxiang, Xia Haibin, Chen Jiawen, Wang Bo, Wu Sheng, Xie Fei, Feng Jianhua, Cen Zhidong, Luo Wei
Department of Neurology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China.
Department of Neurology, Zhuji People's Hospital of Zhejiang Province, Shaoxing, China.
Mov Disord. 2024 Dec;39(12):2190-2198. doi: 10.1002/mds.30004. Epub 2024 Sep 4.
Primary familial brain calcification (PFBC) is a monogenic disorder characterized by bilateral calcifications in the brain. The genetic basis remains unknown in over half of the PFBC patients, indicating the existence of additional novel causative genes. NAA60 was a recently reported novel causative gene for PFBC.
The aim was to identify the probable novel causative gene in an autosomal recessive inherited PFBC family.
We performed a comprehensive genetic study on a consanguineous Chinese family with 3 siblings diagnosed with PFBC. We evaluated the effect of the variant in a probable novel causative gene on the protein level using Western blot, immunofluorescence, and coimmunoprecipitation. Possible downstream pathogenic mechanisms were further explored in gene knockout (KO) cell lines and animal models.
We identified a PFBC co-segregated homozygous variant of c.460_461del (p.D154Lfs*113) in NAA60. Functional assays showed that this variant disrupts NAA60 protein localization to Golgi and accelerated protein degradation. The mutant NAA60 protein alters its interaction with the PFBC-related proteins PiT2 and XPR1, affecting intracellular phosphate homeostasis. Further mass spectrometry analysis in NAA60 KO cell lines revealed decreased expression of multiple brain calcification-associated proteins, including reduced folate carrier (RFC), a folate metabolism-related protein.
Our study replicated the identification of NAA60 as a novel causative gene for autosomal recessive PFBC, demonstrating our causative variant leads to NAA60 loss of function. The NAA60 loss of function disrupts not only PFBC-related proteins (eg, PiT2 and XPR1) but also a wide range of other brain calcification-associated membrane protein substrates (eg, RFC), and provided a novel probable pathogenic mechanism for PFBC. © 2024 International Parkinson and Movement Disorder Society.
原发性家族性脑钙化（PFBC）是一种单基因疾病，其特征为脑部双侧钙化。超过半数的PFBC患者的遗传基础仍不清楚，这表明存在其他新的致病基因。NAA60是最近报道的一种新的PFBC致病基因。
旨在确定一个常染色体隐性遗传的PFBC家族中可能的新致病基因。
我们对一个有3名被诊断为PFBC的兄弟姐妹的近亲中国家庭进行了全面的遗传学研究。我们使用蛋白质免疫印迹法、免疫荧光法和免疫共沉淀法评估了一个可能的新致病基因中的变异在蛋白质水平上的影响。在基因敲除（KO）细胞系和动物模型中进一步探索了可能的下游致病机制。
我们在NAA60基因中鉴定出一个与PFBC共分离的纯合变异c.460_461del（p.D154Lfs*113）。功能分析表明，该变异破坏了NAA60蛋白在高尔基体中的定位，并加速了蛋白质降解。突变的NAA60蛋白改变了其与PFBC相关蛋白PiT2和XPR1的相互作用，影响细胞内磷酸盐稳态。在NAA60基因敲除细胞系中进行的进一步质谱分析显示，多种脑钙化相关蛋白的表达降低，包括与叶酸代谢相关的蛋白——还原型叶酸载体（RFC）。
我们的研究重复了NAA60作为常染色体隐性PFBC新致病基因的鉴定，证明我们发现的致病变异导致NAA60功能丧失。NAA6失功能不仅破坏了PFBC相关蛋白（如PiT2和XPR1），还破坏了广泛的其他脑钙化相关膜蛋白底物（如RFC），并为PFBC提供了一种新的可能致病机制。© 2024国际帕金森和运动障碍协会。
