Penetrance estimation of Alzheimer disease in SORL1 loss-of-function variant carriers using a family-based strategy and stratification by APOE genotypes

Genome Med. 2022 Jun 28;14(1):69. doi: 10.1186/s13073-022-01070-6.


Background: Alzheimer disease (AD) is a common complex disorder with a high genetic component. Loss-of-function (LoF) SORL1 variants are one of the strongest AD genetic risk factors. Estimating their age-related penetrance is essential before putative use for genetic counseling or preventive trials. However, relative rarity and co-occurrence with the main AD risk factor, APOE-ε4, make such estimations difficult.

Methods: We proposed to estimate the age-related penetrance of SORL1-LoF variants through a survival framework by estimating the conditional instantaneous risk combining (i) a baseline for non-carriers of SORL1-LoF variants, stratified by APOE-ε4, derived from the Rotterdam study (N = 12,255), and (ii) an age-dependent proportional hazard effect for SORL1-LoF variants estimated from 27 extended pedigrees (including 307 relatives ≥ 40 years old, 45 of them having genotyping information) recruited from the French reference center for young Alzheimer patients. We embedded this model into an expectation-maximization algorithm to accommodate for missing genotypes. To correct for ascertainment bias, proband phenotypes were omitted. Then, we assessed if our penetrance curves were concordant with age distributions of APOE-ε4-stratified SORL1-LoF variant carriers detected among sequencing data of 13,007 cases and 10,182 controls from European and American case-control study consortia.

Results: SORL1-LoF variants penetrance curves reached 100% (95% confidence interval [99-100%]) by age 70 among APOE-ε4ε4 carriers only, compared with 56% [40-72%] and 37% [26-51%] in ε4 heterozygous carriers and ε4 non-carriers, respectively. These estimates were fully consistent with observed age distributions of SORL1-LoF variant carriers in case-control study data.

Conclusions: We conclude that SORL1-LoF variants should be interpreted in light of APOE genotypes for future clinical applications.

Keywords: APOE; Alzheimer; Expectation-maximization algorithm; Lifetime risk; Missing genotypes; Pedigree; Penetrance; SORL1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alzheimer Disease* / genetics
  • Apolipoproteins E / genetics
  • Case-Control Studies
  • Genotype
  • Humans
  • LDL-Receptor Related Proteins* / genetics
  • Membrane Transport Proteins* / genetics
  • Penetrance


  • ApoE protein, human
  • Apolipoproteins E
  • LDL-Receptor Related Proteins
  • Membrane Transport Proteins
  • SORL1 protein, human