The major allele of the alanine:glyoxylate aminotransferase gene: nine novel mutations and polymorphisms associated with primary hyperoxaluria type 1

Abstract

We describe nine novel mutations and polymorphisms occurring on the major allele of the human alanine:glyoxylate aminotransferase gene in patients with primary hyperoxaluria type 1, an autosomal recessive disease resulting from a deficiency of the liver peroxisomal enzyme alanine:glyoxylate aminotransferase (AGT; EC 2.6.1.44). The PH1 mutations include two small frameshift mutations, 327delG and 117_118insCA, a large deletion spanning exon 9 and portions of the flanking introns, a splice junction mutation, IVS6+5G>C, and two missense mutations, G161R and S218L. Expression studies of the two missense mutations indicated very little enzymatic activity associated with either of them. Three polymorphisms in the coding sequence were also identified, I279T, A280V, and T235T. Expression studies of I279T and A280V suggested essentially normal AGT activity. I279T, found in two cases, was located on a 33_34insC allele. A280V and T235T were both located on the same allele as IVS6+5G>C. We have also identified recurrences of previously reported rare mutations, 33delC, IVS7-1G>C, and IVS4-1G>A. Five of the six novel PH1 mutations occurred in a compound heterozygous state with either of two common PH1 mutations, G170R or 33_34insC. S218L was apparently homozygous in two individuals. These findings contribute to our overall picture of heterogeneity of mutations in PH1 and the AGT major allele.