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New insights into cystinuria: 40 new mutations, genotype-phenotype correlation, and digenic inheritance causing
M Font-Llitjós1, M Jiménez-Vidal, L Bisceglia
1Centre of Medical and Molecular Genetics (IRO), Hospital Duran i Reynals, Barcelona, Spain.
Journal of Medical Genetics
|January 7, 2005
Summary
Digenic inheritance rarely causes cystinuria, with most cases linked to single gene mutations in SLC3A1 or SLC7A9. Mixed types involve both genes, but digenic inheritance has a minor impact on aminoaciduria.
Area of Science:
- Genetics
- Molecular Biology
- Biochemistry
Background:
- Cystinuria is a genetic disorder affecting amino acid reabsorption in the kidneys.
- Understanding genotype-phenotype correlations is crucial for diagnosing and managing cystinuria.
- The role of digenic inheritance in cystinuria requires further elucidation.
Purpose of the Study:
- To clarify the genotype-phenotype correlation in cystinuria.
- To investigate the contribution of digenic inheritance to cystinuria.
- To analyze mutations in SLC3A1 and SLC7A9 genes.
Main Methods:
- Screening of 164 probands for mutations in SLC3A1 and SLC7A9.
- Classification of probands based on urine excretion of cystine and dibasic amino acids.
- Analysis of obligate heterozygote phenotypes.
Main Results:
- Mutations in SLC3A1 and SLC7A9 were identified in 97% of probands, with 40 new mutations discovered.
- Type A heterozygotes typically showed phenotype I, while Type B heterozygotes showed phenotype non-I.
- Digenic inheritance (mutations in both genes) was observed in two families, leading to greater aminoaciduria.
Conclusions:
- Digenic inheritance is an infrequent cause of cystinuria with a limited impact on aminoaciduria.
- Mutational analysis can be gene-specific for Type I (SLC3A1) and Type non-I (SLC7A9) probands.
- For mixed cystinuria types, analysis of both SLC3A1 and SLC7A9 is recommended, prioritizing SLC7A9.