Identification of galactose-1-phosphate uridyl transferase gene common mutations in dried blood spots

The California newborn screening program uses newborns' dried blood spots (DBS) to screen for more than 45 genetic disorders. Deficiency of galactose-1-phosphate uridyl transferase (GALT) is one of the metabolic genetic disorders screened using newborn DBS. During follow-up tests, common mutations of the GALT gene have been identified using whole blood samples. To avoid the stress of drawing an additional blood sample from newborns who are identified as presumptive positive for galactosemia, we developed a method to test common mutations in the GALT gene using blood spots.

This method involves DNA extraction from DBS, followed by polymerase chain reaction (PCR), and single nucleotide extension (SNE). SNE products were detected by capillary electrophoresis.

In a double-blind study, GALT gene common mutations/variants: IVS2-2A>G, p.S135L, p.T138M, p.Q188R, p.L195P, p.Y209C, p.L218L, p.K285N, and p.N314D were detected in seventy-three DBS which had previously been screened and confirmed as positive in the California Newborn Screening Program. Mutations found using blood spots gave 100% concordance with mutations from previously genotyped whole blood samples.

This blood spot method decreases the genomic test turnaround time of GALT screened positive patients and potentially reduces emotional stress on families required to provide an additional blood draw.