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

Alagille Syndrome: Unraveling the Complexities of Genotype-Phenotype Relationships and Exploring Avenues for Improved Diagnosis and Treatment

Alagille syndrome (ALGS) is a rare genetic disorder caused by mutations in the JAG1 and NOTCH2 genes, leading to a wide range of clinical manifestations. This review explores the complex genetic and clinical landscape of ALGS, emphasizing the challenges in understanding genotype-phenotype relationships due to its rarity and the lack of suitable research models. The review projects a clinical overview of the disease, emphasizing the influence of potential gene modifiers on its clinical presentation and the lack of mechanistic studies for over 100 mutations identified in the last 24 years from various populations, representing a significant gap in our current knowledge and advocating for further exploration. The review addresses the diagnostic challenges posed by the variable expressivity and overlapping symptoms of ALGS. It summarizes current treatment options and discusses emerging approaches such as antisense oligonucleotides (ASOs) and gene therapies. Further, the need for improved diagnostic tools, a deeper understanding of the underlying mechanisms, and the development of targeted therapies are emphasized using zebrafish and mice models, as well as genome editing for variant analysis and stem cell organoid models for disease modeling and drug discovery. The importance of cohort-based studies in understanding the natural history and outcomes of ALGS in diverse populations is highlighted. The review concludes by emphasizing the need for multi-disciplinary collaborative research to address the challenges in ALGS diagnosis, prognosis, and treatment, particularly for underrepresented populations.

Case Report: Novel JAG1 gene mutations in two infants with alagille syndrome characterized by cholestasis

Background

Infants with Alagille syndrome (ALGS) need to be promptly differentiated from biliary atresia (BA) at an early stage. ALGS is an autosomal, dominant, multisystem disorder with variable phenotypic penetrance caused by heterozygous mutations in JAG1 or NOTCH2, which encode the Notch signaling pathway.

Case presentation

We report two cases, both with cholestatic jaundice as the main manifestation, in which BA was excluded and finally diagnosed as ALGS based on characteristic facial features, serological tests, imaging, laparoscopic cholangiography, pathology and genetic findings. Both cases are novel mutant genes on chromosome 20 that have not been reported in the literature. The mutation in patient 1 was a novel heterozygous nonsense mutation (NM_000214 exon20, c.2419G > T, p.E807Ter), which was a spontaneous mutation. Followed up to 1 year and 6 months, the symptoms resolved with ursodeoxycholic acid and cholestyramine, and the jaundice has now subsided. Patient 2 was a novel heterozygous frameshift mutation (NM_000214 exon19, c.2367-2368dupTC, p.P790Lfs*31), which was inherited from his mother. This patient was followed up to 9 months and is currently awaiting liver transplantation.

Conclusion

Both cholestatic infants reported combined to exclude BA, avoid Kasai portoenterostomy (KPE), and definitively diagnose ALGS. Broadening the spectrum of JAG1 gene mutations.