Functional characterization of novel variants found in patients with suspected Fabry disease

Clin Chim Acta. 2022 Sep 1;534:156-160. doi: 10.1016/j.cca.2022.07.012.

PMID: 35870541

Patrícia Varela-Calais, Priscila Nicolicht, Renan Paulo Martin

Highlights: This paper presents four novel variants found in patients with suspicion of Fabry disease (FD).

Abstract

Background: The X-linked disorder Fabry disease (FD), which is uncommon and underdiagnosed, is brought on by a deficit in or lack of the lysosomal hydrolase α-Galactosidase A. The symptoms of FD, which can differ greatly across men and women in the same family, are directly related to the mutation in the gene encoding α-Galactosidase A (GLA) and the residual activity of the enzyme.

Objective: This article discusses four novel variants that were discovered in patients who may have FD.

Results: Enzymatic activity and/or DNA sequencing were used to test the patients for FD, and the results revealed four novel GLA missense variants. Site-directed mutagenesis was used to verify if these variations would be pathogenic. Mammalian cells were transfected with GLA wild-type and mutant plasmids, and RNA and proteins were collected for study of expression and enzymatic activity. The GLA variants that the patients had included p.Ile133Asn, p.Lys140Thr, p.Lys168Gln, and p.Pro323Thr. Three variants and one tolerated variant had pathogenic potential, according to in vitro study. The variant p.Lys140Thr, which provided 22% of residual activity, was regarded a mild variant leading to non-classical phenotype. The variants p.Ile133Asn and p.Lys168Gln showed no residual activity and, consequently, leading to classical phenotype. The variant p.Pro323Thr showed 66.7% of residual activity, which is insufficient to produce FD on its own.

Keywords: Fabry disease, GLA gene, Missense variant, Novel variant, α-Galactosidase A