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Successful Linkage Analysis in Classical Phenylketonuria Families Followed by Direct Sequencing and Mutation
Insights
Linkage analysis offers a reliable method for identifying carriers in phenylketonuria (PKU) families. This approach is effective even without prior knowledge of specific causative mutations, aiding in genetic screening.
Area of Science:
- Genetics
- Metabolic Disorders
Background:
- Phenylketonuria (PKU) is a common inherited metabolic disorder.
- PKU prevalence is higher in the Middle East due to consanguinity.
- Identifying PKU carriers is crucial for genetic counseling.
Purpose of the Study:
- To evaluate linkage analysis as a carrier detection method for PKU.
- To assess the reliability of linkage analysis in Iranian PKU families.
- To explore the utility of novel genetic markers and primers.
Main Methods:
- Enrolled ten Iranian PKU families.
- Employed linkage analysis with PAH gene-linked markers (VNTR, PAHSTR, XmnI).
- Utilized new primers for PCR, Sanger sequencing, and capillary electrophoresis (CE) for validation.
Main Results:
- Successfully genotyped nine out of ten families using linkage analysis.
- Confirmed the specificity of new primers via Sanger sequencing.
- Validated linkage analysis results with direct mutation detection in half of the families.
Conclusions:
- Linkage analysis is a powerful tool for PKU carrier detection, especially in previously unscreened families.
- The approach shows potential for PKU preliminary diagnosis, autozygosity confirmation, and prenatal/preimplantation genetic testing.
- Labeled primers and CE facilitate fast, cost-effective, and reliable mutation detection for PKU and hyperphenylalaninemia.
Background:
Phenylketonuria (PKU) is the most common disorder of inborn errors of metabolism. Prevalence of PKU is about 1:10000 live births; however, due to high rate of consanguinity in the Middle East and North of Africa the prevalence of PKU is more than in other areas. It is estimated between 1:2600 in Turkey and 1:3672 in Iran. The best way to identify carriers in PKU families is studying causative mutations, but this approach could be costly and time consuming. As a result, linkage analysis can be considered as a reliable way to detect carriers.
Methods:
Ten non-related classical PKU families from Iran-Fars province were enrolled. Linkage analysis was performed through application of highly linked genetic markers to the PAH gene (VNTR, PAHSTR, and XmnI marker) with new designed primers for polymerase chain reaction (PCR). Reliability of approach was assessed by Sanger sequencing, mutation detection, and capillary electrophoresis (CE).
Results:
Through application of linkage analysis, nine out of ten families were genotyped successfully. Heterozygosity of chromosome 12 was not detected in any of the enrolled PKU patients. Specificity of new designed primers for linkage analysis was confirmed by Sanger dideoxy sequencing. Results obtained from linkage analysis were confirmed by direct sequencing and detecting causative mutations in half of the genotyped families. All the results were the same as the linkage analysis results. Labeled primers were capable and linkage analysis by CE was successful.
Conclusions:
Linkage analysis is a powerful and reliable approach for detecting carriers in PKU families which have not been previously screened for causative mutations. We suggest studying the feasibility of the approach in preliminary diagnosis of PKU and confirming autozygosity of chromosome 12, prenatal diagnosis, and preimplantation genetic testing. Also, we recommend using labeled primers for constructing faithful local PKU associated haplotype databases to provide fast, cheap, and reliable detection of causative mutations in new cases of hyperphenylalaninemia.
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