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Identification of four novel PCDH19 Mutations and prediction of their functional impact
Emanuela Leonardi1, Stefano Sartori2, Marilena Vecchi3
1Molecular Genetics of Neurodevelopment, Department of Women's and Children's Health, University of Padua, Padua, Italy.
Insights
This study investigates novel mutations in the PCDH19 gene, linked to epilepsy and intellectual disability (ID) in girls. The research uses computational methods to assess mutation impact, revealing varied molecular effects and their correlation with disease severity.
Area of Science:
- Genetics and Molecular Biology
- Neuroscience
- Biochemistry
Background:
- The PCDH19 gene encodes protocadherin-19, crucial for neuronal connections.
- Mutations in PCDH19 cause epilepsy and intellectual disability (ID) primarily in females.
- Pathogenicity assessment of novel PCDH19 variants is challenging due to limited male phenotypes.
Purpose of the Study:
- To evaluate the pathogenicity of four novel PCDH19 mutations.
- To elucidate the molecular mechanisms underlying PCDH19-related disorders.
- To correlate mutation effects with clinical phenotypes.
Main Methods:
- Integrated approach combining segregation analysis and in silico computational methods.
- Comparative analysis of multiple computational prediction tools for mutation effects.
- Homology modeling to generate structural models of PCDH19 EC-domains for wild-type and mutant comparisons.
Main Results:
- Four novel PCDH19 mutations were analyzed for their pathogenic potential.
- In silico analysis revealed diverse molecular impacts: altered functional residues, impaired EC-domain stability, and truncated protein formation.
- A frame-shift mutation resulted in a truncated protein lacking the intracellular domain.
- The most severe phenotype was observed in a girl with a putative loss-of-function mutation.
Conclusions:
- Novel PCDH19 mutations exhibit varied molecular mechanisms contributing to disease.
- Computational and segregation analyses are effective for assessing variant pathogenicity.
- Understanding mutation-specific effects can inform genotype-phenotype correlations in PCDH19 disorders.
Abstract:
The PCDH19 gene encodes protocadherin-19, a transmembrane protein with six cadherin (EC) domains, containing adhesive interfaces likely to be involved in neuronal connection. Over a hundred mostly private mutations have been identified in girls with epilepsy, with or without intellectual disability (ID). Furthermore, transmitting hemizygous males are devoid of seizures or ID, making it difficult to establish the pathogenic nature of newly identified variants. Here, we describe an integrated approach to evaluate the pathogenicity of four novel PCDH19 mutations. Segregation analysis has been complemented with an in silico analysis of mutation effects at the protein level. Using sequence information, we compared different computational prediction methods. We used homology modeling to build structural models of two PCDH19 EC-domains, and compared wild-type and mutant models to identify differences in residue interactions or biochemical properties of the model surfaces. Our analysis suggests different molecular effects of the novel mutations in exerting their pathogenic role. Two of them interfere with or alter functional residues predicted to mediate ligand or protein binding, one alters the EC-domain folding stability; the frame-shift mutation produces a truncated protein lacking the intracellular domain. Interestingly, the girl carrying the putative loss of function mutation presents the most severe phenotype.
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