ABSTRACT
The R408W phenylketonuria mutation in Europe has arisen by recurrent mutation in the human phenylalanine hydroxylase (PAH) locus and is associated with two major PAH haplotypes. R408W-2.3 exhibits a west-to-east cline of relative frequency reaching its maximum in the Balto-Slavic region, while R408W-1.8 exhibits an east-to-west cline peaking in Connacht, the most westerly province of Ireland. Spatial autocorrelation analysis has demonstrated that the R408W-2.3 cline, like that of R408W-1.8, is consistent with a pattern likely to have been established by human dispersal. Genetic diversity within wild-type and R408W chromosomes in Europe was assessed through variable number tandem repeat (VNTR) nucleotide sequence variation and tetranucleotide short tandem repeat (STR) allelic associations. Wild-type VNTR-8 chromosomes exhibited two major cassette sequence organizations: (a1)5-b3-b2-c1 and (a1)5-b5-b2-c1. R408W-1.8 was predominantly associated with (a1)5-B5-B2-C1. Both wild-type vntr-3 and r408w-2.3 chromosomes exhibited a single invariant cassette sequence organization, a2-b2-c1. STR allele distributions associated with the cassette variants were consistent with greater diversity in the wild-type VNTR-8 lineage and were suggestive of different levels of diversity between R408W-1.8 and R408W-2.3. The finding of greater genetic diversity within the wild-type VNTR-8 lineage compared to VNTR-3 suggests that VNTR-8 may be older within the European population. However, in the absence of a more extensive STR data-set, no such conclusions are possible for the respective R408W mutant lineages.
