Linkage disequilibrium between phenylketonuria and RFLP haplotype 1 at the phenylalanine hydroxylase locus in Portugal.
RFLPs of 36 normal and 41 mutant alleles at the phenylalanine hydroxylase locus were determined in 31 Portuguese kindreds. A total of 14 haplotypes including 10 normal and 7 mutant alleles were observed. Almost 75% of all mutant alleles were confined within only two haplotypes, namely haplotype 9 (17.1%) and haplotype 1 (56.1%). This frequency of mutant haplotype 1 in Portugal is, to our knowledge, the highest for this mutant haplotype in all studies reported to date. Other mutant haplotypes were either rare (haplotype 2, 9.7%) or totally absent (haplotype 3, 0%). Only 24.5% of all mutant alleles were found to consistently carry identified mutations, particularly R261Q (9.8%), R252W (3.3%), R408W (1.6%) and delta I94 (3.3%). A new mutation, L249F, located in the seventh exon of the gene, accounted for 6.5% of all mutant alleles in our series. Interestingly, this mutant genotype was consistently associated with mutant haplotype 1 (P less than 0.01), as also observed for the R261Q mutation. It appears, therefore, that mutant haplotype 1 is genotypically heterogeneous in Portugal and that more than two mutations account for its prevalence in this country.
Unité de Recherches sur les Handicaps Génétiques de l'Enfant INSERM U-12, Hôpital des Enfants-Malades, Paris, France.
C
C
Caillaud
L
L
Vilarinho
A
A
Vilarinho
F
F
Rey
M
M
Berthelon
R
R
Santos
S
S
Lyonnet
M L
ML
Briard
R V
RV
Osorio
J
J
Rey
D000483:Alleles; D001483:Base Sequence; D005260:Female; D006239:Haplotypes; D006801:Humans; D015810:Linkage Disequilibrium / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010651:Phenylalanine Hydroxylase / Q000235:genetics*; D010661:Phenylketonurias / Q000201:enzymology* / Q000235:genetics; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length
D010651:Phenylalanine Hydroxylase