Two Novel Mutations in the JAG1 Gene in Pediatric Patients with Alagille Syndrome: The First Case Series in Czech Republic.

BACKGROUND: Alagille syndrome (ALGS) is a highly variable multisystem disorder inherited in an autosomal dominant pattern with incomplete penetration. The disorder is caused by mutations in the JAG1 gene, only rarely in the NOTCH2 gene, which gives rise to malformations in multiple organs. Bile duct paucity is the main characteristic feature of the disease. METHODS: Molecular-genetic examination of genes JAG1 and NOTCH2 in four probands of Czech origin who complied with the diagnostic criteria of ALGS was performed using targeted next-generation sequencing of genes JAG1 and NOTCH2. Segregation of variants in a family was assessed by Sanger sequencing of parental DNA. RESULTS: Mutations in the JAG1 gene were confirmed in all four probands. We identified two novel mutations: c.3189dupG and c.1913delG. Only in one case, the identified JAG1 mutation was de novo. None of the parents carrying JAG1 pathogenic mutation was diagnosed with ALGS. CONCLUSION: Diagnosis of the ALGS is complicated due to the absence of clear genotype-phenotype correlations and the extreme phenotypic variability in the patients even within the same family. This fact is of particular importance in connection to genetic counselling and prenatal genetic testing.

Types of congenital nonsyndromic ichthyoses.

Congenital ichthyoses are a very heterogeneous group of diseases manifested by dry, rough and scaling skin. In all forms of ichthyoses, the skin barrier is damaged to a certain degree. Congenital ichthyoses are caused by various gene mutations. Clinical manifestations of the individual types vary as the patient ages. Currently, the diagnosis of congenital ichthyoses is based on molecular analysis, which also allows a complete genetic counseling and genetic prevention. It is appropriate to refer the patients to specialized medical centers, where the cooperation of a neonatologist, a pediatric dermatologist, a geneticist and other specialists is ensured.

Inherited ichthyoses: molecular causes of the disease in Czech patients.

Inherited ichthyoses belong to a large and heterogeneous group of mendelian disorders of cornification, and can be distinguished by the quality and distribution of scaling and hyperkeratosis, by other dermatologic and extracutaneous involvement, and by inheritance. We present the genetic analysis results of probands with X-linked ichthyosis, autosomal recessive congenital ichthyosis, keratinopathic ichthyosis, and a patient with Netherton syndrome. Genetic diagnostics was complemented by in silico missense variant analysis based on 3D protein structures and commonly used prediction programs to compare the yields of these two approaches to each other. This analysis revealed various structural defects in proteins coded by mutated genes while no defects were associated with known polymorphisms. Two patients with pathogenic variants in the ABCA12 gene have a premature termination codon mutation on one allele and a silent variant on the second. The silent variants c.69G > A and c.4977G > A are localised in the last nucleotide of exon 1 and exon 32, respectively, and probably affect mRNA splicing. The phenotype of both patients is very severe, including a picture harlequin foetus after birth; later (at 3 and 6 years of age, respectively) ectropin, eclabion, generalised large polygonal scaling and erythema.