Haplotype distribution at the phenylalanine hydroxylase locus in PKU families from the Moravian area of Czechoslovakia

Mutation spectrum and phenylalanine hydroxylase RFLP/VNTR background in 44 Romanian phenylketonuric alleles

The mutation spectrum and polymorphic haplotype background in 22 Romanian families have been analysed in this study using the restriction digestion of phenylalanine hydroxylase (PAH) regions specifically amplified or the DGGE/direct sequencing methods. Eleven PAH mutations specifically associated with six mutant haplotypes were detected. In spite of the relative heterogeneity of the molecular defects in the PAH gene, three mutations covered almost 70% of all alleles: R408W, 47.72%, 21/44; K363fsdelG 13.63%, 6/44; and P225T 6.81%, 3/44. Among these, R408W, the most frequent mutation in our population, represented 50% of all the phenylketonuric (PKU) chromosomes. Splice mutation IVS12nt1g-->a affected two PAH alleles (4.54%); the remaining seven mutations were rare, each having an effect on just one chromosome (1/44), resulting in a relative frequency of 2.27%. A high frequency was observed in our PKU samples for the relatively uncommon mutations, K363fsdelG and P225T mutation, suggesting a possible founder effect at origin. Within the investigated panel, these mutations, both very rare among other Caucasians were exclusively linked to haplotype 5.8 and 1.7, respectively. These results provide a basis for the development of a routine molecular analysis of Romanian PKU families.

Mutation and haplotype analysis of phenylalanine hydroxylase alleles in classical PKU patients from the Czech Republic: identification of four novel mutations

Mutations, haplotypes, and other polymorphic markers in the phenylalanine hydroxylase (PAH) gene were analysed in 133 unrelated Czech families with classical phenylketonuria (PKU). Almost 95% of all mutant alleles were identified, using a combination of PCR and restriction analysis, denaturing gradient gel electrophoresis (DGGE), and sequencing. A total of 30 different mutations, 16 various RFLP/VNTR haplotypes, and four polymorphisms were detected on 266 independent mutant chromosomes. The most common molecular defect observed in the Czech population was R408W (54.9%). Each of the other 29 mutations was present in no more than 5% of alleles and 13 mutations were found in only one PKU allele each (0.4%). Four novel mutations G239A, R270fsdel5bp, A342P, and IVS11nt-8g-->a were identified. In 14 (5.1%) alleles, linked to four different RFLP/VNTR haplotypes, the sequence alterations still remain unknown. Our results confirm that PKU is a heterogeneous disorder at the molecular level. Since there is evidence for the gene flow coming from northern, western, and southern parts of Europe into our Slavic population, it is clear that human migration has been the most important factor in the spread of PKU alleles in Europe.

Phenylketonuria mutations and their relation to RFLP haplotypes at the PAH locus in Czech PKU families

A detailed study of the mutant phenylalanine hydroxylase (PAH) gene from the eastern part of the Czech Republic (Moravia) is reported. A total of 190 mutant alleles from 95 phenylketonuria (PKU) families were analyzed for 21 prevalent Caucasian mutations and restriction fragment length polymorphism/variable number of tandem repeats (RFLP/VNTR) haplotypes. Eighty per cent of all mutant alleles were found to carry 11 mutations. The most common molecular defect was the mutation R408W (55.3%), with a very high degree of homozygosity (34.6%). Each of four other mutations (R158Q, R243X, G272X, IVS12nt1) accounted for more than 3% of PKU alleles. Rarely present were mutations IVS10nt546 (2.6%), R252W (2.6%), L48S (2.1%), R261Q (1.6%), Y414C (1.0%) and 165T (0.5%). Mutations that have been predominantly described in southern Europe (IVS7nt1, A259V, Y277D, R241H, T278N) were not detected. A total of 14 different mutant haplotypes were observed. Three unusual genotype-haplotype associations were identified (R158Q on haplotypes 2.3 and 7.8 and R252W on haplotype 69.3). There was a strong association between the mutation R408W and haplotype 2.3 (54.7%). Heterogeneity was found at mutations R408W (haplotypes 2.3 and 5.9), R158Q (haplotypes 4.3, 2.3 and 7.8) and IVS10nt546 (haplotypes 6.7 and 34.7). The molecular basis of PKU in the Moravian area appears to be relatively homogeneous in comparison with other southern and western European populations, thus providing a good starting point for prenatal diagnosis and early clinical classification.