Overview

Clinical Phenotype: Alzheimer's Disease
Position: (GRCh38/hg38):Chr11:121577364 G>A
Position: (GRCh37/hg19):Chr11:121448073 G>A
dbSNP ID: NA
Coding/Non-Coding: Coding
DNA Change: Substitution
Expected Protein Consequence: Missense
Codon Change: GAC to AAC
Reference Isoform: SORL1 Isoform 1 (2214 aa)
Genomic Region: Exon 25

Findings

In a pan-European cohort of 1,255 Alzheimer’s cases and 1,938 controls from the European Early Onset Dementia Consortium, a Spanish AD patient was found to be a heterozygous carrier of this variant (Verheijen et al., 2016). The patient began exhibiting symptoms at 59 years and there was a family history of AD.

No additional carriers were found among 5,198 AD cases and 4,491 controls from the Alzheimer’s Disease Sequencing Project from whom whole-exome sequencing data were available, 1,779 AD cases and 1,273 controls from the Alzheimer Disease Exome Sequencing France project, 332 cases and 676 controls of European ancestry from the United Kingdom and North America (Campion et al., 2019), or 640 cases and 1268 controls from a multi-center Dutch sample (Holstege et al., 2017).

This variant is classified as likely pathogenic by the criteria of Holstege et al. (Holstege et al., 2017).

Functional Consequences

The SORL1 protein contains 11 complement-type repeats (CRs). A majority of known SORL1 ligands, including APP, bind to the CR cluster, and ligand binding is Ca²⁺-dependent. In proteins with CR domains, each CR contains four amino acids whose acidic side chains, together with the backbone carbonyls of two additional residues, form an octahedral Ca²⁺ cage critical for proper folding of the domain. Residue 1182 is a component of the Ca²⁺ cage in CR3.

Andersen and colleagues predicted that variants affecting residues that contribute their acidic side chains to the Ca²⁺ cages are highly likely to increase AD risk (Andersen et al., 2023). Domain mapping of disease mutations revealed that several variants associated with medical conditions—in genes including LDLR (familial hypercholesterolemia), LRP2 (intellectual disability, Stickler syndrome), LRP5 (exudative vitreoretinopathy 4), TMPRSS3 (deafness), and TMPRSS6 (iron-refractory iron deficiency anemia)—occur in Ca²⁺-cage residues. Furthermore, analysis of data from the Alzheimer’s Disease Sequencing Project and the Alzheimer Disease European Sequencing consortium showed that SORL1 Ca²⁺-cage variants significantly increased the risk of AD (OR = infinity), leading to the suggestion that these variants be considered causative for AD (Andersen et al., 2023).

The following Ca²⁺-cage variants are listed in the Alzforum database: D1108N, D1182N, D1219G, D1261G, D1267N, D1267E, D1345N, D1439N, D1502G, D1535N, D1545N, D1545G, D1545E. With the exception of D1267E, all carriers of these variants were Alzheimer’s casesThe variant was predicted to be damaging by SIFT, disease-causing by Mutation Taster, and probably damaging by PolyPhen-2 (Verheijen et al., 2016).

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References

Paper Citations

1. Verheijen J, Van den Bossche T, van der Zee J, Engelborghs S, Sanchez-Valle R, Lladó A, Graff C, Thonberg H, Pastor P, Ortega-Cubero S, Pastor MA, Benussi L, Ghidoni R, Binetti G, Clarimon J, Lleó A, Fortea J, de Mendonça A, Martins M, Grau-Rivera O, Gelpi E, Bettens K, Mateiu L, Dillen L, Cras P, De Deyn PP, Van Broeckhoven C, Sleegers K. A comprehensive study of the genetic impact of rare variants in SORL1 in European early-onset Alzheimer's disease. Acta Neuropathol. 2016 Aug;132(2):213-24. Epub 2016 Mar 30 PubMed.
2. Campion D, Charbonnier C, Nicolas G. SORL1 genetic variants and Alzheimer disease risk: a literature review and meta-analysis of sequencing data. Acta Neuropathol. 2019 Aug;138(2):173-186. Epub 2019 Mar 25 PubMed.
3. Holstege H, van der Lee SJ, Hulsman M, Wong TH, van Rooij JG, Weiss M, Louwersheimer E, Wolters FJ, Amin N, Uitterlinden AG, Hofman A, Ikram MA, van Swieten JC, Meijers-Heijboer H, van der Flier WM, Reinders MJ, van Duijn CM, Scheltens P. Characterization of pathogenic SORL1 genetic variants for association with Alzheimer's disease: a clinical interpretation strategy. Eur J Hum Genet. 2017 Aug;25(8):973-981. Epub 2017 May 24 PubMed.
4. Andersen OM, Monti G, Jensen AM, deWaal M, Hulsman M, Olsen JG, Holstege H. Relying on the relationship with known disease-causing variants in homologous proteins to predict pathogenicity of SORL1 variants in Alzheimer's disease. 2023 Feb 27 10.1101/2023.02.27.524103 (version 1) bioRxiv.

Further Reading

No Available Further Reading