Mutation and Linkage Analysis in Genetic Counseling for Phenylketonuria in Kuwait

Objective: Phenylketonuria (PKU) is caused by mutations in the PAH gene. More than 250 PAH mutations have been identified, and their distribution among different populations varies significantly. Though PKU is prevalent in Kuwait, the molecular bases of the underlying genetic variants have never been studied. Methods: DNA from 20 PKU patients belonging to 11 families of Arabic origin as well as 30 healthy relatives was extracted using a ‘salting-out’ method. DNA samples were analyzed by polymerase chain reaction (PCR)/restriction fragment length polymorphism (RFLP) tests for 5 common PAH mutations (IVS10nt546, R261Q, IVS12nt1, IVS2nt1, R408W). Linkage analysis and PAH haplotyping was carried out by the study of variable number tandem repeat and BglI, PvuII-a, PvuII-b, MspI, XmnI polymorphism by PCR or PCR/RFLP tests. Results: Seven patients from 4 families were found to be homozygous for IVS10nt546, thus proving the frequency of this mutation among PKU chromosomes in Kuwait to be 36.4%. The four other PAH mutations were absent among the patients studied. The linkage analysis was informative in all but 1 of the families. Seven PAH haplotypes were identified among 22 PKU chromosomes from Kuwait. All the IVS10nt546 chromosomes had identical haplotype.