To elucidate the novel molecular cause in two unrelated consanguineous families with autosomal recessive intellectual disability. A combination of homozygosity mapping and exome sequencing was used to Show more
To elucidate the novel molecular cause in two unrelated consanguineous families with autosomal recessive intellectual disability. A combination of homozygosity mapping and exome sequencing was used to locate the plausible genetic defect in family F162, while only exome sequencing was followed in the family PKMR65. The protein 3D structure was visualized with the University of California-San Francisco Chimera software. All five patients from both families presented with severe intellectual disability, aggressive behavior, and speech and motor delay. Four of the five patients had microcephaly. We identified homozygous missense variants in LINGO1, p.(Arg290His) in family F162 and p.(Tyr288Cys) in family PKMR65. Both variants were predicted to be pathogenic, and segregated with the phenotype in the respective families. Molecular modeling of LINGO1 suggests that both variants interfere with the glycosylation of the protein. LINGO1 is a transmembrane receptor, predominantly found in the central nervous system. Published loss-of-function studies in mouse and zebrafish have established a crucial role of LINGO1 in normal neuronal development and central nervous system myelination by negatively regulating oligodendrocyte differentiation and neuronal survival. Taken together, our results indicate that biallelic LINGO1 missense variants cause autosomal recessive intellectual disability in humans. Show less
Mendelian cardiomyopathies and arrhythmias are characterized by an important genetic heterogeneity, rendering Sanger sequencing very laborious and expensive. As a proof of concept, we explored multipl Show more
Mendelian cardiomyopathies and arrhythmias are characterized by an important genetic heterogeneity, rendering Sanger sequencing very laborious and expensive. As a proof of concept, we explored multiplex targeted high-throughput sequencing (HTS) as a fast and cost-efficient diagnostic method for individuals suffering from Mendelian cardiac disorders. We designed a DNA capture assay including all exons from 130 genes involved in cardiovascular Mendelian disorders and analysed simultaneously four samples by multiplexing. Two patients had familial hypertrophic cardiomyopathy (HCM) and two patients suffered from long QT syndrome (LQTS). In patient 1 with HCM, we identified two known pathogenic missense variants in the two most frequently mutated sarcomeric genes MYH7 and MYBPC. In patient 2 with HCM, a known acceptor splice site variant in MYBPC3 was found. In patient 3 with LQTS, two missense variants in the genes SCN5A and KCNQ were identified. Finally, in patient 4 with LQTS a known missense variant was found in MYBPC3, which is usually mutated in patients with cardiomyopathy. Our results showed that multiplex targeted HTS works as an efficient and cost-effective tool for molecular diagnosis of heterogeneous disorders in clinical practice and offers new insights in the pathogenesis of these complex diseases. Show less