Hyperinsulinism/hyperammonemia syndrome caused by biallelic SLC25A36 mutation

VARista: a free web platform for streamlined whole-genome variant analysis across T2T, hg38, and hg19

With the increasing importance of genomic data in understanding genetic diseases, there is an essential need for efficient and user-friendly tools that simplify variant analysis. Although multiple tools exist, many present barriers such as steep learning curves, limited reference genome compatibility, or costs. We developed VARista, a free web-based tool, to address these challenges and provide a streamlined solution for researchers, particularly those focusing on rare monogenic diseases. VARista offers a user-centric interface that eliminates much of the technical complexity typically associated with variant analysis. The tool directly supports VCF files generated using reference genomes hg19, hg38, and the emerging T2T, with seamless remapping capabilities between them. Features such as gene summaries and links, tissue and cell-specific gene expression data for both adults and fetuses, as well as automated PCR design and integration with tools such as SpliceAI and AlphaMissense, enable users to focus on the biology and the case itself. As we demonstrate, VARista proved effective in narrowing down potential disease-causing variants, prioritizing them effectively, and providing meaningful biological context, facilitating rapid decision-making. VARista stands out as a freely available and comprehensive tool that consolidates various aspects of variant analysis into a single platform that embraces the forefront of genomic advancements. Its design inherently supports a shift in focus from technicalities to critical thinking, thereby promoting better-informed decisions in genetic disease research. Given its unique capabilities and user-centric design, VARista has the potential to become an essential asset for the genomic research community. https://VARista.link.

Mitochondrial targets in hyperammonemia: Addressing urea cycle function to improve drug therapies

The urea cycle (UC) is a critically important metabolic process for the disposal of nitrogen (ammonia) produced by amino acids catabolism. The impairment of this liver-specific pathway induced either by primary genetic defects or by secondary causes, namely those associated with hepatic disease or drug administration, may result in serious clinical consequences. Urea cycle disorders (UCD) and certain organic acidurias are the major groups of inherited rare diseases manifested with hyperammonemia (HA) with UC dysregulation. Importantly, several commonly prescribed drugs, including antiepileptics in monotherapy or polytherapy from carbamazepine to valproic acid or specific antineoplastic agents such as asparaginase or 5-fluorouracil may be associated with HA by mechanisms not fully elucidated. HA, disclosing an imbalance between ammoniagenesis and ammonia disposal via the UC, can evolve to encephalopathy which may lead to significant morbidity and central nervous system damage. This review will focus on biochemical mechanisms related with HA emphasizing some poorly understood perspectives behind the disruption of the UC and mitochondrial energy metabolism, namely: i) changes in acetyl-CoA or NAD+ levels in subcellular compartments; ii) post-translational modifications of key UC-related enzymes, namely acetylation, potentially affecting their catalytic activity; iii) the mitochondrial sirtuins-mediated role in ureagenesis. Moreover, the main UCD associated with HA will be summarized to highlight the relevance of investigating possible genetic mutations to account for unexpected HA during certain pharmacological therapies. The ammonia-induced effects should be avoided or overcome as part of safer therapeutic strategies to protect patients under treatment with drugs that may be potentially associated with HA.

Bridging the gaps: recent advances in diagnosis, care, and outcomes in congenital hyperinsulinism

PURPOSE OF REVIEW

To highlight advances in congenital hyperinsulinism (HI), including newly described molecular mechanisms of disease, novel therapeutic interventions, and improved understanding of long-term outcomes.

RECENT FINDINGS

Important advances have been made elucidating the molecular mechanisms responsible for HI. Non-coding variants in HK1 have been found to cause aberrant hexokinase expression. Inactivating mutations in SLC25A36 have been identified in children with features of the hyperinsulinism hyperammonemia syndrome. Low-level mosaic mutations in known HI genes have been detected in cases of 'genetic testing negative' HI. Identification and localization of focal HI lesions remains a priority, since focal HI can be cured with surgery. Use of 68 Ga-NODAGA-exendin-4 PET has been proposed to localize focal lesions. Additional studies are needed before this technique replaces 18 F-DOPA PET as standard of care. Treatment options for children with diffuse HI remain limited. The long-acting somatostatin analog, lanreotide, was shown to significantly improve glycemic control in a large series of children with HI. New therapies are under development, with promising preliminary results. Long-term quality of life and neurodevelopmental outcomes remain suboptimal.

SUMMARY

Advanced genetic and epigenomic analytic techniques have uncovered novel molecular mechanisms of HI. Development of new drugs holds promise to improve long-term outcomes for individuals with HI.