Aagenaes syndrome/lymphedema cholestasis syndrome 1 is caused by a founder variant in the 5'-untranslated region of UNC45A

A New Unc45a 5'utr Variant In Patients With Aagenaes Syndrome

Aagenaes syndrome, also known as lymphoedema cholestasis syndrome 1 (LCS1), is a rare autosomal recessive disorder characterized by neonatal cholestasis and chronic lymphedema, primarily affecting the lower extremities. The genetic basis for this syndrome was recently linked to a variant in the 5'-untranslated region (5'-UTR) of the UNC45A gene, located on chromosome 15q. This study aimed to identify the genetic mutations associated with Aagenaes syndrome in two siblings and to explore their clinical implications. Whole-exome sequencing (WES) was conducted on two siblings with neonatal cholestasis and lymphedema. WES identified a single base pair change in the 5'-untranslated region (5'-UTR) of the UNC45A gene (c.-88G>A) in both siblings. Additionally, both were heterozygous for an exonic loss-of-function variant (c.1591C>T; p.Arg531Ter) in UNC45A. Clinically, both siblings presented with neonatal cholestasis and lymphedema; however, one sibling developed severe liver failure, requiring a liver transplant. Despite carrying the same variants, the clinical outcomes differed between the two patients. The identification of a novel 5'-UTR variant (c.-88G>A), along with an exonic variant in UNC45A, expands the genetic and clinical understanding of Aagenaes syndrome. This study confirms the involvement of the 5'-UTR region of UNC45A in the disease pathogenesis, while demonstrating that Aagenaes syndrome is not exclusively associated with the previously reported c.-98G>T variant found in Norwegian cases. These findings underscore the importance of genetic screening for accurate diagnosis and management of Aagenaes syndrome and provide new insights into the critical regulatory role of the 5'-UTR in disease development. Further research is needed to elucidate the mechanisms underlying phenotypic variability in this rare disorder. Evaluation of mRNA and protein levels would have been valuable to better understand the functional effects of these variants; however, due to current resource constraints, such studies could not be conducted.

Differences in bile acid profiles between cholestatic diseases - Development of a high throughput assay for dried bloodspots

BACKGROUND

Cholestasis causes accumulation of bile acids (BAs) and changes the circulating bile acid profile. Quantification of circulating BAs in dried bloodspots (DBS) may demonstrate obstruction of bile flow and altered bile acid metabolism in the liver. High sample throughput enables rapid screening of cholestatic diseases.

MATERIALS AND METHODS

Ultra high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) was used for optimizing separation and detection of the primary unconjugated BAs cholic acid (CA) and chenodeoxycholic acid (CDCA); the secondary unconjugated BAs ursodeoxycholic acid (UDCA), hyodeoxycholic acid (HDCA) and deoxycholic acid (DCA), as well as the glycine- and taurine-conjugated variants of CA, CDCA, DCA and UDCA. Donor blood was obtained to prepare DBS calibrators and quality controls for method development and validation.

RESULTS

We developed a quantitative bile acid assay with a run-time of two minutes, and one-step sample preparation of 3.2 mm DBS discs. Validation results demonstrated overall good performance and was considered fit for purpose. Children with Alagille syndrome, Aagenaes syndrome and alpha-1 antitrypsin deficiency had increased BAs in DBS from newborn screening samples compared with age matched controls, and had different bile acids profiles.

CONCLUSION

We propose that our high throughput assay allows bile acid profiling in DBS that can be a valuable assessment tool for early screening of cholestasis in children. Assaying BAs in dried bloodspots is key for early detection of cholestasis, and provides transferability to a newborn screening setting.

Intracellular Trafficking Defects in Congenital Intestinal and Hepatic Diseases

Enterocytes and liver cells fulfill important metabolic and barrier functions and are responsible for crucial vectorial secretive and absorptive processes. To date, genetic diseases affecting metabolic enzymes or transmembrane transporters in the intestine and the liver are better comprehended than mutations affecting intracellular trafficking. In this review, we explore the emerging knowledge on intracellular trafficking defects and their clinical manifestations in both the intestine and the liver. We provide a detailed overview including more investigated diseases such as the canonical, variant and associated forms of microvillus inclusion disease, as well as recently described pathologies, highlighting the complexity and disease relevance of several trafficking pathways. We give examples of how intracellular trafficking hubs, such as the apical recycling endosome system, the trans-Golgi network, lysosomes, or the Golgi-to-endoplasmic reticulum transport are involved in the pathomechanism and lead to disease. Ultimately, understanding these processes could spark novel therapeutic approaches, which would greatly improve the quality of life of the affected patients.

Regulation of Epithelial and Endothelial Barriers by Molecular Chaperones

The integrity and permeability of epithelial and endothelial barriers depend on the formation of tight junctions, adherens junctions, and a junction-associated cytoskeleton. The establishment of this junction-cytoskeletal module relies on the correct folding and oligomerization of its protein components. Molecular chaperones are known regulators of protein folding and complex formation in different cellular compartments. Mammalian cells possess an elaborate chaperone network consisting of several hundred chaperones and co-chaperones. Only a small part of this network has been linked, however, to the regulation of intercellular adhesions, and the systematic analysis of chaperone functions at epithelial and endothelial barriers is lacking. This review describes the functions and mechanisms of the chaperone-assisted regulation of intercellular junctions. The major focus of this review is on heat shock protein chaperones, their co-chaperones, and chaperonins since these molecules are the focus of the majority of the articles published on the chaperone-mediated control of tissue barriers. This review discusses the roles of chaperones in the regulation of the steady-state integrity of epithelial and vascular barriers as well as the disruption of these barriers by pathogenic factors and extracellular stressors. Since cytoskeletal coupling is essential for junctional integrity and remodeling, chaperone-assisted assembly of the actomyosin cytoskeleton is also discussed.