NUS1 encodes the Nogo-B receptor, a critical regulator for unfolded protein reaction (UPR) signaling. Although several loss-of-function variants of NUS1 have been identified in patients with developmental and epileptic encephalopathy (DEE), the role of the NUS1 variant in Lennox-Gastaut syndrome (LGS), a severe child-onset DEE, remains unknown. In this study, we identified two de novo variants of NUS1, a missense variant (c.868 C > T/p.R290C) and a splice site variant (c.792-2 A > G), in two unrelated LGS patients using trio-based whole-exome sequencing performed in a cohort of 165 LGS patients. Both variants were absent in the gnomAD population and showed a significantly higher observed number of variants than expected genome-wide. The R290C variant was predicted to damage NUS1 and decrease its protein stability. The c.792-2 A > G variant caused premature termination of the protein. Knockdown of NUS1 activated the UPR pathway, resulting in apoptosis of HEK293T cells. Supplementing cells with expression of wild-type NUS1, but not the mutant (R290C), rescued UPR activation and apoptosis in NUS1 knockdown cells. Compared to wild-type Drosophila, seizure-like behaviors and excitability in projection neurons were significantly increased in Tango14 (homolog of human NUS1) knockdown and Tango14^R290C/+ knock-in Drosophila. Additionally, abnormal development and a small body size were observed in both mutants. Activated UPR signaling was also detected in both mutants. Thus, NUS1 is a causative gene for LGS with dominant inheritance. The pathogenicity of these variants is related to the UPR signaling activation, which may be a common pathogenic mechanism of DEE.

NUS1编码 Nogo-B 受体，这是未折叠蛋白反应 (UPR) 信号传导的关键调节因子。尽管在发育性癫痫性脑病 (DEE) 患者中已发现NUS1的几种功能丧失变异，但NUS1变异在 Lennox-Gastaut 综合征 (LGS)（一种严重的儿童发病 DEE）中的作用仍不清楚。在这项研究中，我们在两名不相关的 LGS 患者中鉴定了NUS1的两种从头变异，即错义变异 (c.868 C > T/p.R290C) 和剪接位点变异 (c.792-2 A > G)。对 165 名 LGS 患者进行了基于三重奏的全外显子组测序。这两种变体在 gnomAD 群体中都不存在，并且观察到的变体数量明显高于全基因组范围内的预期。 R290C 变体预计会损害 NUS1 并降低其蛋白质稳定性。 c.792-2 A > G 变体导致蛋白质过早终止。NUS1的敲低激活了 UPR 通路，导致 HEK293T 细胞凋亡。在细胞中补充野生型NUS1的表达，而不是突变型（R290C）的表达，可以挽救NUS1敲低细胞中的UPR激活和细胞凋亡。与野生型果蝇相比， Tango14（人类NUS1同源物）敲低和Tango14 ^R290C/+敲入果蝇的癫痫样行为和投射神经元兴奋性显着增加。此外，在两种突变体中都观察到发育异常和体型较小。在两种突变体中也检测到激活的 UPR 信号。因此，NUS1是具有显性遗传的LGS的致病基因。这些变异体的致病性与UPR信号激活有关，这可能是DEE常见的致病机制。