Primary hyperoxaluria type 1 and brachydactyly mental retardation syndrome caused by a novel mutation in AGXT and a terminal deletion of chromosome 2

Abstract

Primary hyperoxaluria type 1 (PH1) is an autosomal recessive disorder caused by mutations in the alanine:glyoxylate aminotransferase (AGXT) gene, located on chromosome 2q37. Mutant AGXT leads to excess production and excretion of oxalate, resulting in accumulation of calcium oxalate in the kidney, and progressive loss of renal function. Brachydactyly mental retardation syndrome (BDMR) is an autosomal dominant disorder, caused by haploinsufficiency of histone deacetylase 4 (HDAC4), also on chromosome 2q37. It is characterized by skeletal abnormalities and developmental delay. Here, we report on a girl who had phenotypes of both PH1 and BDMR. PCR-sequencing of the coding regions of AGXT showed a novel missense mutation, c.32C>G (p.Pro11Arg) inherited from her mother. Functional analyses demonstrated that it reduced the enzymatic activity to 31% of the wild-type and redirected some percentage of the enzyme away from the peroxisome. Microsatellite and array-CGH analyses indicated that the proband had a paternal de novo telomeric deletion of chromosome 2q, which included HDAC4. To our knowledge, this is the first report of PH1 and BDMR, with a novel AGXT mutation and a de novo telomeric deletion of chromosome 2q.