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.