Identification of two new nucleotide mutations (HPRT_Utrecht and HPRT_Madrid) in exon 3 of the human hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene

Abstract

Mutations in the X-linked hypoxanthine-guanine phosphoribosyl transferase gene (HPRT) result in deficiencies of HPRT enzyme activity, which may cause either a severe form of gout or Lesch-Nyhan syndrome depending on the residual enzyme activity. Mutations leading to these diseases are heterogeneous and include DNA base substitutions, DNA deletions, DNA base insertions and errors in RNA splicing. Identification of mutations has been performed at the RNA and DNA level. Sequencing genomic DNA of the HPRT gene offers the possibility of direct diagnostic analysis independent on the expression of the mature HPRT mRNA. We describe a Dutch and a Spanish family, in which the Lesch-Nyhan syndrome and a severe partial HPRT-deficient phenotype, respectively, were diagnosed. Direct sequencing of the exons coding for the HPRT gene was performed in both families. Two new exon 3 mutations have been identified. At position 16676, the normally present G was substituted by an A in the Dutch kindred (HPRT_Utrecht), and led to an arginine for glycine change at residue 70. At position 16680, the G was substituted by a T in the Spanish family (HPRT_Madrid); this substitutes a valine for glycine at residue 71. These new mutations are located within one of the clusters of hotspots in exon 3 of the HPRT gene in which HPRT_Yale and HPRT_{New Haven} have previously been identified.