Identification of a novel R21X mutation in the liver-type arginase gene (ARG1) in four Portuguese patients with argininemia.

Argininemia is a rare autossomal recessive disorder caused by deficiency in the cytosolic liver-type arginase enzyme (L-arginine urea-hydrolase; E.C. 3.5.3.1). In order to investigate the molecular basis for argininemia in four unrelated Portuguese patients (two from northern Portugal and two from Madeira Island) we performed a DNA sequence analysis of all the exons and exon/intron boundaries of the liver-type arginase gene (ARG1). All patients were found to be homozygous for a newly identified C ->T transition in codon 21 (exon 2) substituting arginine for a premature stop codon (R21X: CGA to TGA) and generating a NlaIII restriction site. Restriction digestion following PCR amplification of ARG1 exon 2 confirmed the presence of the mutation.