An A-to-G mutation at the +3 position of intron 8 of the HEXA gene is associated with exon 8 skipping and Tay-Sachs disease.

Tay-Sachs disease (TSD) results from a deficiency of beta-hexosaminidase A (EC 3.2.1.52) activity. A child with late-infantile TSD was found to have two HEXA mutations, 986 + 3A-->G (A-->G at the +3 position of intron 8) and 533G-->A, associated with the variant B1 form of TSD. We were able to detect exon 8-deleted, but no correctly spliced HEXA mRNA, from the non-533G-->A allele in this patient. This suggests that 986 + 3A-->G results in missplicing and, together with 533G-->A, TSD.