Molecular basis of phenylketonuria in Venezuela: Presence of two novel null mutations

Abstract

This report describes the mutational spectrum and linked haplotypes of the phenylalanine hydroxylase gene in Venezuela. In this study, we have detected European mutations such as IVS10nt‐11, R243Q, and R408W on the same haplotype background (6.7, 1.8, and 2.3, respectively) as in Europe. In this sample, we have found two novel mutations: S349L detected in two homozygous siblings on the background of haplotype 6.7, and a small deletion, P314fsdelC, that results in a frameshift and a premature stop codon detected on the background of haplotype 4.3. The definite demonstration that mutation S349L results in a nonfunctional protein was shown by expression analysis in prokaryotic and eukaryotic systems. This mutation results in an unstable phenylalanine hydroxylase (PAH) protein completely devoid of enzymatic activity well correlated with the severe form of the disease exhibited by the homozygous patients. Hum Mutat 11:354–359, 1998. © 1998 Wiley‐Liss, Inc.

Mutations of the phenylalanine hydroxylase (PAH) gene in Brazilian patients with phenylketonuria

“…The wide genetic heterogeneity observed in the present study and the analysis of the association between mutations and haplotype indicate a predominantly European origin of these mutations as a consequence of historical migrations, a fact that has also been described for other Latin-American populations [Desviat et al, 1993;Pérez et al, 1996;De Lucca et al, 1998;Pérez et al, 1999]. The Brazilian population originates from a complex racial mixture predominantly of western and southern Europeans, African blacks, and Amerindians.…”

In vitro expression analysis of R68G and R68S mutations in phenylalanine hydroxylase gene.

“…Expression analysis was performed in Escherichia coli, using pMAL-c2 expression system. The in-frame gene encoding a fusion protein with human phenylalanine hydroxylase and maltose binding protein (MBP) was obtained as described previously [6]. PAH activity was measured using conversion of [ 14 C]phenylalanine to [ 14 C]tyrosine, with total cell lysate protein and fusion protein purified using affinity chromatography (amylose resin) as described previously [7].…”