Hypomorphic variants of SEL1L-HRD1 ER-associated degradation are associated with neurodevelopmental disorders
Huilun H. Wang, Liangguang L. Lin, Zexin J. Li, Xiaoqiong Wei, Omar Askander, Gerarda Cappuccio, Mais O. Hashem, Laurence Hubert, Arnold Munnich, Mashael Alqahtani, Qi Pang, Margit Burmeister, You Lu, Karine Poirier, Claude Besmond, Shengyi Sun, Nicola Brunetti-Pierri, Fowzan S. Alkuraya, Ling Qi
Huilun H. Wang, Liangguang L. Lin, Zexin J. Li, Xiaoqiong Wei, Omar Askander, Gerarda Cappuccio, Mais O. Hashem, Laurence Hubert, Arnold Munnich, Mashael Alqahtani, Qi Pang, Margit Burmeister, You Lu, Karine Poirier, Claude Besmond, Shengyi Sun, Nicola Brunetti-Pierri, Fowzan S. Alkuraya, Ling Qi
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Research Article Cell biology

Hypomorphic variants of SEL1L-HRD1 ER-associated degradation are associated with neurodevelopmental disorders

Abstract

Recent studies using cell type–specific knockout mouse models have improved our understanding of the pathophysiological relevance of suppressor of lin-12-like–HMG-CoA reductase degradation 1 (SEL1L-HRD1) endoplasmic reticulum–associated (ER-associated) degradation (ERAD); however, its importance in humans remains unclear, as no disease variant has been identified. Here, we report the identification of 3 biallelic missense variants of SEL1L and HRD1 (or SYVN1) in 6 children from 3 independent families presenting with developmental delay, intellectual disability, microcephaly, facial dysmorphisms, hypotonia, and/or ataxia. These SEL1L (p.Gly585Asp, p.Met528Arg) and HRD1 (p.Pro398Leu) variants were hypomorphic and impaired ERAD function at distinct steps of ERAD, including substrate recruitment (SEL1L p.Gly585Asp), SEL1L-HRD1 complex formation (SEL1L p.Met528Arg), and HRD1 activity (HRD1 p.Pro398Leu). Our study not only provides insights into the structure-function relationship of SEL1L-HRD1 ERAD, but also establishes the importance of SEL1L-HRD1 ERAD in humans.

Authors

Huilun H. Wang, Liangguang L. Lin, Zexin J. Li, Xiaoqiong Wei, Omar Askander, Gerarda Cappuccio, Mais O. Hashem, Laurence Hubert, Arnold Munnich, Mashael Alqahtani, Qi Pang, Margit Burmeister, You Lu, Karine Poirier, Claude Besmond, Shengyi Sun, Nicola Brunetti-Pierri, Fowzan S. Alkuraya, Ling Qi

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Figure 3

SEL1L and HRD1 variants are hypomorphic with impaired ERAD function toward misfolded endogenous and model substrates.

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SEL1L and HRD1 variants are hypomorphic with impaired ERAD function tow...
(A and B) Western blot analysis of known ERAD endogenous substrates IRE1α, OS9, and CD147 in KI HEK293T cells, with quantitation shown in B. n = 4–16 (IRE1α); n = 4–12 (OS9); n = 3–12 (CD147). OS9.1 and OS9.2 were quantified together as OS9. SEL1L–/– and HRD1–/– HEK293T cells were included as controls. (C and D) Cycloheximide (CHX) chase analysis of known ERAD endogenous substrates IRE1α, OS9, and CD147 in KI HEK293T cells, with quantitation shown in D. n = 3–8 (IRE1α); n = 3–6 (OS9); n = 3–8 (CD147). SEL1L and HRD1 variants were analyzed separately with their own WT controls. Quantitation normalized to WT controls. Western blot data for ERAD KO samples shown in Supplemental Figure 3. (E and F) Reducing and nonreducing SDS-PAGE and Western blot analysis of HMW aggregates of proAVP(G57S) in KI HEK293T cells, with quantitation shown in F. n = 3–6 for group. n, individual cell samples. For A, C, and E, SEL1L and HRD1-KO HEK293T cells were included as controls and quantitated as ERAD KO. The replicates in Western blot are technical replicates. Data are represented as means ± SEM. Quantitation of the band intensities was compared using 1-way ANOVA with post hoc Tukey-Kramer test (B and F) or 2-way ANOVA followed by multiple comparisons test (D). For B, comparisons between different letters (a–d) represents P < 0.05. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.