Large-scale functional LIPA variant characterization to improve birth prevalence estimates of lysosomal acid lipase deficiency.

Abstract

Lysosomal acid lipase (LAL) deficiency is an autosomal recessive disorder caused by LIPA gene mutations that disrupt LAL activity. We performed in vitro functional testing of 149 LIPA variants to increase the understanding of the variant effects on LAL deficiency and to improve disease prevalence estimates. Chosen variants had been reported in literature or population databases. Functional testing was done by plasmid transient transfection and LAL activity assessment. We assembled a set of 165 published LAL deficient patient genotypes to evaluate this assay's effectiveness to recapitulate genotype/phenotype relationships. Rapidly progressive LAL deficient patients showed negligible enzymatic activity (<1%), whereas patients with childhood/adult LAL deficiency typically have 1-7% average activity. We benchmarked six in silico variant effect prediction algorithms with these functional data. PolyPhen-2 was shown to have a superior area under the receiver operating curve performance. We used functional data along with Genome Aggregation Database (gnomAD) allele frequencies to estimate LAL deficiency birth prevalence, yielding a range of 3.45-5.97 cases per million births in European-ancestry populations. The low estimate only considers functionally assayed variants in gnomAD. The high estimate computes allele frequencies for variants absent in gnomAD, and uses in silico scores for unassayed variants. Prevalence estimates are lower than previously published, underscoring LAL deficiency's rarity.

• Authors: Guillermo Del Angel, Andrew T Hutchinson, Nina K Jain, Chris D Forbes, John Reynders
• Journal: Human mutation (Hum Mutat) Vol. 40 Issue 11 Pg. 2007-2020 (11 2019) ISSN: 1098-1004 [Electronic] United States
• PMID: 31180157 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2019 The Authors. Human Mutation Published by Wiley Periodicals, Inc.

Chemical References

• LIPA protein, human
• Sterol Esterase

Topics

• Algorithms
• Gene Expression
• Genetic Association Studies
• Genetic Predisposition to Disease
• Genetic Variation
• Genotype
• Humans
• Models, Genetic
• Mutation
• Phenotype
• Prevalence
• ROC Curve
• Sterol Esterase (genetics)
• Wolman Disease (epidemiology, genetics)