Functional and biological studies of α-galactosidase A variants with uncertain significance from newborn screening in Taiwan

• Published in: Molecular genetics and metabolism Vol. 123; no. 2; pp. 140 - 147
• Main Authors: Liao, Hsuan-Chieh, Hsu, Ting-Rong, Young, Leslie, Chiang, Chuan-Chi, Huang, Chun-Kai, Liu, Hao-Chuan, Niu, Dau-Ming, Chen, Yann-Jang
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.02.2018
• Subjects: Alpha-galactosidase; alpha-Galactosidase - blood; alpha-Galactosidase - genetics; Biological Assay; Biomarkers - blood; Blood Specimen Collection; Dried Blood Spot Testing; Fabry disease; Fabry Disease - diagnosis; Fabry Disease - epidemiology; Fabry Disease - genetics; Fabry Disease - metabolism; Female; Humans; Infant, Newborn; Lyso-Gb3; Male; Mutation; Neonatal Screening; Newborn screening; Taiwan - epidemiology; Variants of uncertain significance; Taiwan; Fabry disease; Newborn screening; Variants of uncertain significance; Alpha-galactosidase; Lyso-Gb3
• ISSN: 1096-7192; 1096-7206; 1096-7206
• DOI: 10.1016/j.ymgme.2017.06.002

Fabry disease is an X-linked disorder resulted from deficiency of α-galactosidase A (GLA) activity. In Taiwan, a total of 792,247 newborns were screened from 2008 to 2014 in two newborn screening centers, and 13 variants of uncertain significance (VOUS) in the GLA gene were identified. To determine whether these variants were pathogenic or not, functional, biochemical, clinical and pedigree analyses were performed. In vitro functional assay was established through site-directed mutagenesis, and four in silico tools were used to predict pathogenesis. The enzyme activity of dried blood spots and plasma metabolite lyso-Gb3 level from subjects with the variants were measured. Additionally, clinical manifestations were evaluated extensively from the subjects and their relatives. Our results revealed that p.G104V, p.I232T, p.D322H, and p.G360C all exhibited relatively low residual enzyme activities and elevated plasma lyso-Gb3 level. These data strongly suggest that these Fabry mutations may cause classical or later-onset phenotypes. In contrast, neither significantly clinical symptoms nor elevated lyso-Gb3 level was found in cases with p.P60S, p.A108T, p.S304T, p.R356Q, and p.P362T variants, which may be non-pathogenic or milder forms of Fabry variants. More data need to be included for the patients with p.N53D, p.P210S, p.M296L, and p.K391T variants. The established system provides us more information to classify these GLA variants. •Thirteen variants of uncertain significance in the GLA gene were identified in 792,247 newborns from newborn screening in Taiwan.•Variants of p.G104V, p.I232T, p.D322H, and p.G360C may cause classical or later-onset of Fabry disease; while variants of p.P60S, p.A108T, p.S304T, p.R356Q, and p.P362T may be non-pathogenic or milder forms of Fabry disease.