PHENYLKETONURIA MUTATION ANALYSIS IN NORTHERN-IRELAND - A RAPID STEPWISE APPROACH

We present a multistep approach for the rapid analysis of phenylketonu ria (PKU) mutations. In the first step, three common mutations and a p olymorphic short tandem repeat (STR) system are rapidly analyzed with a fluorescent multiplex assay. In the second step, mini-haplotypes com bining STR and VNTR data are used to determine rare mutations likely t o be present in an investigated patient, which are then confirmed by r estriction enzyme analysis. The remaining mutations are analyzed with denaturant gradient-gel electrophoresis and sequencing. The first two steps together identify both mutations in 90%-95% of PKU patients, and results can be obtained within 2 d. We have investigated 121 Northern Irish families with hyperphenylalaninemia, including virtually all pa tients born since 1972, and have found 34 different mutations on 241 o f the 242 mutant alleles. Three mutations (R408W, I65T, and F39L) acco unt for 57.5% of mutations, while 14 mutations occur with a frequency of 1%-6%. The present analysis system is efficient and inexpensive and is particularly well suited to routine mutation analysis in a diagnos tic setting.