Individuals With Normal GLA Gene Sequence May Present Abnormally Spliced Alpha-Galactosidase mRNA Transcripts

Abstract

Background: Deficient lysosomal α-galactosidase activity leads to intracellular accumulation of globotriaosylceramide (Gb3), which is the pathologic hallmark of Fabry disease (FD). There are over 750 pathogenic variants identified in the α-galactosidase gene (GLA). In rare patients, the cause of α-galactosidase deficiency is the overexpression of a GLA transcript with a cryptic exon in intron 4, which is physiologically present at trace levels. Objectives: We aim to report abnormally spliced alpha-galactosidase mRNA transcripts found with a cDNA-based GLA genotyping protocol performed in 482 patients. Patients and Methods: Genomic DNA and total RNA specimens were obtained from peripheral blood leukocytes of patients with premature stroke prospectively enrolled in the PORTYSTROKE study, or of patients with possible clinical manifestations of FD who have been referred for molecular diagnostic workup. Results: Approximately 20% of the patients expressed alternatively spliced transcripts of GLA mRNA involving exon 3. We additionally report that such non-canonical transcripts are physiologically expressed at trace levels in healthy individuals, and that their expression in leukocytes markedly increased in blood samples kept at room-temperature for 48 hours before RNA extraction. Conclusions: Production of alternatively spliced GLA transcripts might be involved in the regulation of GLA gene expression, and its deregulated overexpression, particularly if restricted to specific cells or tissues, might be the cause of organ-limited Gb3 pathology. Elucidation of the molecular mechanisms underlying the production of the non-canonical GLA transcripts warrants further investigation, as it may contribute important new data to the understanding of the molecular pathology of FD and Gb3-related disorders.