Fabry Disease: Incidence of the Common Later-Onset α-Galactosidase A IVS4+919G→A Mutation in Taiwanese Newborns—Superiority of DNA-Based to Enzyme-Based Newborn Screening for Common Mutations

Abstract

Fabry disease is a panethnic, X-linked, inborn error of glycosphingolipid metabolism resulting from mutations in the α-galactosidase A gene (GLA) that lead to the deficient activity of the lysosomal enzyme, α-galactosidase A (α-Gal A). Affected males with no α-Gal A activity have the early-onset classic phenotype, whereas those with residual activity present with the lateronset subtype. Recently, we reported that newborn enzyme-based screening using dried blood spots (DBS) in Taiwan revealed a high incidence of newborn males who had the GLA c.936+919G→A (IVS4+919G→A) mutation. This lesion causes cryptic splicing, markedly reducing the amount of wild-type GLA mRNA, and has been found in males with the later-onset Fabry phenotype, manifesting as cardiac, renal and/or cerebrovascular disease. To more accurately determine the incidence of the IVS4+919G→A mutation, 20,063 consecutive newborns were screened by a deoxyribonucleic acid (DNA)-based assay. Of the 10,499 males, 12 (1/875) and 24 of the 9,564 females (1/399) had the mutation. On the basis of these frequencies, the previous newborn enzymebased DBS screening (cutoff: <30% of the normal mean) only identified 67% and 17% of mutation-positive males and females, respectively. The mean DBS α-Gal A activities in the mutation-positive males and females were 23% (1.54 U) and 55% (3.63 U) of normal mean male/female values, respectively. These studies confirm the high incidence of the IVS4+919G→A mutation in the Taiwanese population and indicate that its detectability by enzyme-based DBS screening is unreliable, especially in females. These studies emphasize the superiority of DNA-based newborn screening for common mutations, particularly for X-linked diseases.

Newborn screening for lysosomal storage disorders

“…The diagnosis of asymptomatic carrier females, therefore, is limited to molecular genetic analysis of the GLA gene. 48 However, regardless of the severity of symptoms, male and female patients typically show an increased excretion of GL3 in urine 49 but this urine marker is not reliable during the first few weeks of life, probably because of physiological renal changes in the kidneys. 50 Another disease biomarker detectable in blood is globotriaosylsphingosine, but its usefulness in the neonatal period and in the context of NBS requires more study.…”

Globotriaosylsphingosine (lyso-Gb3) might not be a reliable marker for monitoring the long-term therapeutic outcomes of enzyme replacement therapy for late-onset Fabry patients with the Chinese hotspot mutation (IVS4+919G>A)

“…Another DNA-based newborn screening program for this mutation in Taiwan revealed a higher incidence (1/875 in males and 1/399 in females) [11]. Patients who carried the IVS4 + 919G > A mutation and were older than 40 years had a higher prevalence of hypertrophic cardiomyopathy (72% of males and 35% of females) [12].…”

Using CRISPR/Cas9-Mediated GLA Gene Knockout as an In Vitro Drug Screening Model for Fabry Disease

“…The fibroblasts derived from FD patients with GLA IVS4 + 919G>A mutation—the most common type of GLA mutation in Taiwan—in addition to the alternative splicing that introduces a 57-nucleotide (nt) intronic sequence to the α-Gal A transcript from intron 4 of the gene, have been identified [27,28,29] as expressing a lower level of endogenous GLA enzyme activity and protein expression compared with the fibroblasts derived from healthy subjects (Figure 4A). The GLA IVS4 + 919G>A mutation was confirmed by RT-PCR and DNA sequencing (Figure S1D,E).…”