In addition , each affected child was heterozygous for the G1681A mutation in exon 7 that led to an Ala467Thr substitution in POLG , within the linker region of the protein .
O O O O O O O O O O B-SequenceVariant O O O O O O O O B-SequenceVariant O O B-GeneOrGeneProduct O O O O O O O O O