Per
ClinVar there are 150 recognized pathogenic variants of the GLA gene. None are recognized by a professional society
and none are identified by an expert panel.
According
to Genetests, 51 laboratories in the US offer diagnostic testing related to the
GLA gene. A variety of different
methodologies are offered including Micro-array, Deletion/Duplication/Copy
Number, Quantitative Biochemical Analysis, Sequencing, and Genotyping.
According
to NCBI Genetic Test Registry (GTR), 46 labs in the U.S. offer testing related
to GLA variants which are associated with Fabry’s Disease. Testing methods include Biochemical Genetics
(Analyte, Enzyme Assay) and Molecular Genetics (Sequence analysis of the entire
coding region, Deletion/duplication analysis, Sequence analysis of select exons,
Targeted variant analysis).
Identification
of a potential RFLP test for the 1066C>T variant of the GLA sequence was not
possible as there were no changes in enzyme sites of the codon associated with
this variant. Therefore, ClinVar was used
to identify the 677G>A variant which did result in a new restriction enzyme (Bpu101)
site at position 675 of the ORF of the variant that was not present in the ORF
of the normal GLA gene sequence. (The Bpu101
enzyme is an infrequent cutter with 3 sites in the native GLA sequence as
compared to 4 sites in 677G>A variant sequence.)
Agarose
gel simulations for the Bpu101 enzyme of the native GLA sequence and the
677G>A sequence are depicted below. The additional Bpu101 enzyme site in the 677G>A variant resulted in creating 4 bands (602bp, 322bp, 259bp,235bp) as compared to 3 bands (602bp,494bp,322bp) in the native sequence of the GLA gene.
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| Native GLA sequence |
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| Native GLA sequence |
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| 677G>A variant |
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| 677G>A variant |
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