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Alpha-1 antitrypsin (AAT) deficiency is a genetic disease that can affect both the lung and the liver. The vast majority of patients harbor a mutation in the SERPINA1 gene resulting in a single substitution from glutamic acid to lysine at amino acid position 342 (p.E342K). The AAT encoded by the Z allele (ATZ) is not properly folded and accumulates in the endoplasmic reticulum (ER) of hepatocytes resulting in liver disease through a gain of function mechanism. The liver disease is a prototype of conformational disorder due to protein misfolding and aggregation. Intracellular retention of ATZ triggers a complex injury cascade including autophagy, ER-stress and other mechanisms. Nevertheless, several aspects of the disease pathogenesis are still unclear. I found that ATZ induces activation of c-JUN N-terminal kinase (JNK) and c-JUN signaling in livers of a mouse model (PiZ mice) of the disease. JNK activation was confirmed in human livers of patients homozygous for the Z allele with severe liver disease requiring hepatic transplantation. In mice, genetic ablation of Jnk1 or Jnk2 decreased ATZ levels by reducing c-JUN mediated SERPINA1 expression. Moreover, I have found up-regulation of genes associated with response to ER stress in PiZ mouse livers by expression array profiling. Among the differentially expressed genes, I focused on the CCAAT/Enhancer-Binding Protein Homologous Protein (Chop) that was significantly up-regulated in both mouse and human livers expressing ATZ. To investigate the role of CHOP in ATZ-induced liver damage, I crossed PiZ with Chop null (Chop-/-) mice. Genetic ablation of Chop resulted in a marked reduction of hepatic ATZ levels in juvenile PiZ mice. SERPINA1 mRNA levels in livers of PiZ/Chop-/- mice were also significantly reduced compared to PiZ controls, suggesting that CHOP induces ATZ accumulation by increasing SERPINA1 transcription. CHOP was indeed found to up-regulate SERPINA1 expression through binding with C/EBP? and c-JUN on SERPINA1 regulatory elements. So far, JNK and CHOP have been involved in the pathogenesis of several liver disorders but not in hepatic disease induced by ATZ. The results of my studies show that JNK and CHOP are important players in the disease pathogenesis and are novel therapeutic targets.

Alpha1-antitrypsin deficiency is a genetic disease that can affect both the lung and the liver. The vast majority of patients harbor a mutation in the SERPINA1 gene resulting in a single amino acid substitution that results in an unfolded protein that is prone to polymerization. Therefore, the liver disease is caused by a gain of function mechanism due to accumulation of the mutant Z alpha1-antitrypsin (ATZ) and is a key example of an important disease mechanism induced by protein toxicity. Intracellular retention of ATZ triggers a complex injury cascade including apoptosis and other mechanisms, although several aspects of the disease pathogenesis are still unclear. We show that ATZ induces activation of JNK and c-JUN and genetic ablation of JNK1 or JNK2 decreased ATZ levels in vivo by reducing c-JUN mediated SERPINA1 expression. JNK activation was confirmed in livers of patients homozygous for the Z allele with severe liver disease requiring hepatic transplantation. Treatment of patient-derived induced pluripotent stem cell (iPSCs)-hepatic cells with a JNK inhibitor reduced accumulation of ATZ. In conclusion, these data reveal that JNK is a key pathway in the disease pathogenesis and add new therapeutic entry points for liver disease caused by ATZ. This article is protected by copyright. All rights reserved.

α1 -antitrypsin (AAT) deficiency is one of the most common genetic disorders and the liver disease due to the Z mutant of α1 -antitrypsin (ATZ) is a prototype of conformational disorder due to misfolding of protein with consequent aberrant intermolecular protein aggregation. In the present study, we found that livers of PiZ transgenic mice expressing the human ATZ have altered expression of a network of hepatocyte transcriptional factors including HNF4-α, that is early downregulated and induces a transcriptional repression of ATZ expression. Reduced HNF-4α was associated with activation of β-catenin that regulates liver zonation. Livers of PiZ mice and human patients with AAT deficiency were both found to have a severe perturbation of liver zonation. Functionally, PiZ mice showed a severe defect of ureagenesis, as shown by increased baseline ammonia, and reduced urea production and survival after an ammonia challenge. Downregulation of HNF-4α expression and defective zonation in livers have not been yet recognized as features of the liver disease caused by ATZ and are likely responsible for metabolic disturbances and for the increased risks of hepatocellular carcinoma in patients with AAT deficiency. In conclusion, these findings are consistent with the concept that abnormal AAT protein conformation and intrahepatic accumulation have broad effect on metabolic liver functions. This article is protected by copyright. All rights reserved.

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM, Life-threatening hyperammonemia occurs in both inherited and acquired liver diseases affecting ureagenesis, the main pathway for detoxification of neurotoxic ammonia in mammals. Protein O-GlcNAcylation is a reversible and nutrient-sensitive post-translational modification using as substrate UDP-GlcNAc, the end-product of hexosamine biosynthesis pathway. Here we show that increased liver UDP-GlcNAc during hyperammonemia increases protein O-GlcNAcylation and enhances ureagenesis. Mechanistically, O-GlcNAcylation on specific threonine residues increased the catalytic efficiency for ammonia of carbamoyl phosphate synthetase 1 (CPS1), the rate-limiting enzyme in ureagenesis. Pharmacological inhibition of O-GlcNAcase, the enzyme removing O-GlcNAc from proteins, resulted in clinically relevant reductions of systemic ammonia in both genetic (hypomorphic mouse model of propionic acidemia) and acquired (thioacetamide-induced acute liver failure) mouse models of liver diseases. In conclusion, by fine-tuned control of ammonia entry into ureagenesis, hepatic O-GlcNAcylation of CPS1 increases ammonia detoxification and is a novel target for therapy of hyperammonemia in both genetic and acquired diseases, This work was supported by grants of Fondazione Telethon Italy (to N.B.‐P.), MIUR (PRIN2017 to N.B.‐P.), of the Swiss National Science Foundation (grant 320030_176088 to J.H.), of the US National Institutes of Health grants (R21NS091654 and R01NS100979 both to G.S.L.), of the Spanish Ministry of Science and Innovation (PID2019-105344RB-I00/AEI/10.13039/501100011033 toL.R.D. and E.R.), and by a Wellcome Trust Investigator Award (110061to D.M.F.v.A.)

Multiple sulfatase deficiency (MSD) is an ultrarare lysosomal storage disorder due to deficiency of all known sulfatases. MSD is caused by mutations in the Sulfatase Modifying Factor 1 (SUMF1) gene encoding the enzyme responsible for the post-translational modification and activation of all sulfatases. Most MSD patients carry hypomorph SUMF1 variants resulting in variable degrees of residual sulfatase activities. In contrast, Sumf1 null mice with complete deficiency in all sulfatase enzyme activities, have very short lifespan with significant pre-wean lethality, owing to a challenging preclinical model. To overcome this limitation, we genetically engineered and characterized in mice two commonly identified patient-based SUMF1 pathogenic variants, namely p.Ser153Pro and p.Ala277Val. These pathogenic missense variants correspond to variants detected in patients with attenuated MSD presenting with partial-enzyme deficiency and relatively less severe disease. These novel MSD mouse models have a longer lifespan and show biochemical and pathological abnormalities observed in humans. In conclusion, mice harboring the p.Ser153Pro or the p.Ala277Val variant mimic the attenuated MSD and are attractive preclinical models for investigation of pathogenesis and treatments for MSD.

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We performed whole exome sequencing in individuals from a family with autosomal dominant gastropathy resembling Méné trier disease, a premalignant gastric disorder with epithelial hyperplasia and enhanced EGFR signalling. Méné trier disease is believed to be an acquired disorder, but its aetiology is unknown. In affected members, we found a missense p.V742G variant in MIB2, a gene regulating NOTCH signalling that has not been previously linked to human diseases. The variant segregated with the disease in the pedigree, affected a highly conserved amino acid residue, and was predicted to be deleterious although it was found with a low frequency in control individuals. The purified protein carrying the p.V742G variant showed reduced ubiquitination activity in vitro and white blood cells from affected individuals exhibited significant reductions of HES1 and NOTCH3 expression reflecting alteration of NOTCH signalling. Because mutations of MIB1, the homolog of MIB2, have been found in patients with left ventricle non-compaction (LVNC), we investigated members of our family with Méné trier-like disease for this cardiac abnormality. Asymptomatic left ventricular hypertrabeculation, the mildest end of the LVNC spectrum, was detected in two members carrying the MIB2 variant. Finally, we identified an additional MIB2 variant (p.V984L) affecting protein stability in an unrelated isolated case with LVNC. Expression of both MIB2 variants affected NOTCH signalling, proliferation and apoptosis in primary rat cardiomyocytes. In conclusion, we report the first example of left ventricular hypertrabeculation/LVNC with germline MIB2 variants resulting in altered NOTCH signalling that might be associated with a gastropathy clinically overlapping with Méné trier disease.