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-epsilon 4, 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-epsilon 4, 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-epsilon 4-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-epsilon 4 epsilon 4 carriers only, compared with 56% [40-72%] and 37% [26-51%] in epsilon 4 heterozygous carriers and epsilon 4 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.

Penetrance estimation of Alzheimer disease in SORL1 loss-of-function variant carriers using a family-based strategy and stratification by APOE genotypes / Schramm, Catherine; Charbonnier, Camille; Zaréa, Aline; Lacour, Morgane; Wallon, David; Boland, Anne; Deleuze, Jean-François; Olaso, Robert; Alarcon, Flora; Campion, Dominique; Nuel, Grégory; Nicolas, Gaël; Nacmias, Benedetta. - In: GENOME MEDICINE. - ISSN 1756-994X. - ELETTRONICO. - 14:(2022), pp. 1-15. [10.1186/s13073-022-01070-6]

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

Nacmias, Benedetta
2022

Abstract

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-epsilon 4, 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-epsilon 4, 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-epsilon 4-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-epsilon 4 epsilon 4 carriers only, compared with 56% [40-72%] and 37% [26-51%] in epsilon 4 heterozygous carriers and epsilon 4 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.
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Schramm, Catherine; Charbonnier, Camille; Zaréa, Aline; Lacour, Morgane; Wallon, David; Boland, Anne; Deleuze, Jean-François; Olaso, Robert; Alarcon, Flora; Campion, Dominique; Nuel, Grégory; Nicolas, Gaël; Nacmias, Benedetta
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2158/1286044
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