Functional and pharmacological evaluation of novel GLA variants in Fabry disease identifies six (two de novo) causative mutations and two amenable variants to the chaperone DGJ

Allelic heterogeneity is an important feature of the GLA gene for which almost 900 known genetic variants have been discovered so far. Pathogenetic GLA variants cause alpha-galactosidase A (α-Gal A) enzyme deficiency leading to the X-linked lysosomal storage disorder Fabry disease (FD). Benign GLA i...

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Bibliographic Details
Published in:	Clinica chimica acta Vol. 481; pp. 25 - 33
Main Authors:	Ferri, Lorenzo, Malesci, Duccio, Fioravanti, Antonella, Bagordo, Gaia, Filippini, Armando, Ficcadenti, Anna, Manna, Raffaele, Antuzzi, Daniela, Verrecchia, Elena, Donati, Ilaria, Mignani, Renzo, Cavicchi, Catia, Guerrini, Renzo, Morrone, Amelia
Format:	Journal Article
Language:	English
Published:	Netherlands Elsevier B.V 01-06-2018
Subjects:	1-Deoxygalactonojirimycin Adolescent Adult Aged alpha-Galactosidase - genetics alpha-Galactosidase - metabolism Atypical variants Computational Biology De novo mutation DGJ Fabry Disease - drug therapy Fabry Disease - genetics Fabry Disease - pathology Female Genetic Variation - drug effects Genetic Variation - genetics Humans Lipofectamine Male Middle Aged Molecular Chaperones - pharmacology Mutation RNA, Messenger - genetics Site-directed mutagenesis Atypical variants Lipofectamine 1-Deoxygalactonojirimycin VUS De novo mutation α-Gal A DGJ Site-directed mutagenesis FD
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Summary:	Allelic heterogeneity is an important feature of the GLA gene for which almost 900 known genetic variants have been discovered so far. Pathogenetic GLA variants cause alpha-galactosidase A (α-Gal A) enzyme deficiency leading to the X-linked lysosomal storage disorder Fabry disease (FD). Benign GLA intronic and exonic variants (e.g. pseudodeficient p.Asp313Tyr) have also been described. Some GLA missense variants, previously deemed to be pathogenetic (e.g. p.Glu66Gln and p.Arg118Cys), they have been reclassified as benign after re-evaluation by functional and population studies. Hence, the functional role of novel GLA variants should be investigated to assess their clinical relevance. We identified six GLA variants in 4 males and 2 females who exhibited symptoms of FD: c.159C>G p.(Asn53Lys), c.400T>C p.(Tyr134His), c.680G>C (p.Arg227Pro), c.815A>T p.(Asn272Ile), c.907A>T p.(Ile303Phe) and c.1163_1165delTCC (p.Leu388del). We evaluated their impact on the α-Gal A protein by bioinformatic analysis and homology modelling, by analysis of the GLA mRNA, and by site-directed mutagenesis and in vitro expression studies. We also measured their responsiveness to the pharmacological chaperone DGJ. The six detected GLA variants cause deficient α-Gal A activity and impairment or loss of the protein wild-type structure. We found p.Asn53Lys and p.Ile303Phe variants to be susceptible to DGJ. [Display omitted] •Knowing the clinical significance of a VUS bears correct counselling and therapy.•GLA variants of unknown significance (VUS) cause diagnostic uncertainty.•Functional studies are essential to assess the clinical significance of a GLA VUS.•The T134H, R227P, N272I and L388del variants cause absent α-Gal A activity and FD.•The N53K and I303F variants cause partial α-Gal A deficiency and respond to DGJ.
ISSN:	0009-8981 1873-3492
DOI:	10.1016/j.cca.2018.02.021