IDENTIFICATION OF AN ARGININE(452) TO HISTIDINE SUBSTITUTION IN THE ERYTHROID 5-AMINOLEVULINATE SYNTHETASE GENE IN A LARGE PEDIGREE WITH X-LINKED HEREDITARY SIDEROBLASTIC ANEMIA

The coding region of the erythroid 5-aminolaevulinate synthetase gene (ALAS2) from a large pedigree with pyridoxine responsive X-linked here ditary sideroblastic anaemia was examined for mutations. In three affe cted males from this pedigree, single strand conformational polymorphi sm (SSCP) analysis shea ed anomalous migration of a PCR product spanni ng exon 9. Sequencing of amplified genomic DNA from one of these affec ted males revealed a guanine to adenine transition at nucleotide 1407 of the cDNA sequence in exon 9 of the gene. This mutation results in t he loss of an HhaI restriction enzyme digest site. An HhaI digest assa y demonstrated the presence of this mutation in other affected males b ut not in unaffected males and unrelated individuals The point mutatio n results in an arginine to histidine substitution at amino acid resid ue 452. The arginine residue is conserved in both the erythroid and ho usekeeping ALAS genes in all known vertebrate sequence This arginine i s located in the middle of a predicted alpha-helix.