Increased expression or activation of TRPML1 reduces hepatic storage of toxic Z alpha-1 antitrypsin.

Mutant Z alpha-1 antitrypsin (ATZ) accumulates in globules in the liver and is the prototype of proteotoxic hepatic disease. Therapeutic strategies aiming at clearance of polymeric ATZ are needed. Transient receptor potential mucolipin-1 (TRPML1) is a lysosomal Ca2+ channel that maintains lysosomal homeostasis. In this study, we show that by increasing lysosomal exocytosis, TRPML1 gene transfer or small-molecule-mediated activation of TRPML1 reduces hepatic ATZ globules and fibrosis in PiZ transgenic mice that express the human ATZ. ATZ globule clearance induced by TRPML1 occurred without increase in autophagy or nuclear translocation of TFEB. Our results show that targeting TRPML1 and lysosomal exocytosis is a novel approach for treatment of the liver disease due to ATZ and potentially other diseases due to proteotoxic liver storage.

Up-regulation of miR-34b/c by JNK and FOXO3 protects from liver fibrosis.

α1-Antitrypsin (AAT) deficiency is a common genetic disease presenting with lung and liver diseases. AAT deficiency results from pathogenic variants in the SERPINA1 gene encoding AAT and the common mutant Z allele of SERPINA1 encodes for Z α1-antitrypsin (ATZ), a protein forming hepatotoxic polymers retained in the endoplasmic reticulum of hepatocytes. PiZ mice express the human ATZ and are a valuable model to investigate the human liver disease of AAT deficiency. In this study, we investigated differential expression of microRNAs (miRNAs) between PiZ and control mice and found that miR-34b/c was up-regulated and its levels correlated with intrahepatic ATZ. Furthermore, in PiZ mouse livers, we found that Forkhead Box O3 (FOXO3) driving microRNA-34b/c (miR-34b/c) expression was activated and miR-34b/c expression was dependent upon c-Jun N-terminal kinase (JNK) phosphorylation on Ser574 Deletion of miR-34b/c in PiZ mice resulted in early development of liver fibrosis and increased signaling of platelet-derived growth factor (PDGF), a target of miR-34b/c. Activation of FOXO3 and increased miR-34c were confirmed in livers of humans with AAT deficiency. In addition, JNK-activated FOXO3 and miR-34b/c up-regulation were detected in several mouse models of liver fibrosis. This study reveals a pathway involved in liver fibrosis and potentially implicated in both genetic and acquired causes of hepatic fibrosis.

Cholangiopathies and the noncoding revolution.

PURPOSE OF REVIEW: Noncoding RNAs (ncRNAs), including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) among others, have attracted a great deal of attention for their potential role as master regulators of gene expression and as therapeutic targets. This review focuses on recent advances on the role of ncRNAs in the pathogenesis, diagnosis and treatment of diseases of the cholangiocytes (i.e. cholangiopathies). RECENT FINDINGS: In the recent years, there has been an exponential growth in the knowledge on ncRNAs and their role in cholangiopathies, particularly cholangiocarcinoma. SUMMARY: Although several studies focused on miRNAs as noninvasive biomarkers for diagnosis and staging, several studies also highlighted their functions and provided new insights into disease mechanisms.

CHOP and c-JUN up-regulate the mutant Z α1-antitrypsin, exacerbating its aggregation and liver proteotoxicity.

α1-Antitrypsin (AAT) encoded by the SERPINA1 gene is an acute-phase protein synthesized in the liver and secreted into the circulation. Its primary role is to protect lung tissue by inhibiting neutrophil elastase. The Z allele of SERPINA1 encodes a mutant AAT, named ATZ, that changes the protein structure and leads to its misfolding and polymerization, which cause endoplasmic reticulum (ER) stress and liver disease through a gain-of-function toxic mechanism. Hepatic retention of ATZ results in deficiency of one of the most important circulating proteinase inhibitors and predisposes to early-onset emphysema through a loss-of-function mechanism. The pathogenetic mechanisms underlying the liver disease are not completely understood. C/EBP-homologous protein (CHOP), a transcription factor induced by ER stress, was found among the most up-regulated genes in livers of PiZ mice that express ATZ and in human livers of patients homozygous for the Z allele. Compared with controls, juvenile PiZ/Chop-/- mice showed reduced hepatic ATZ and a transcriptional response indicative of decreased ER stress by RNA-Seq analysis. Livers of PiZ/Chop-/- mice also showed reduced SERPINA1 mRNA levels. By chromatin immunoprecipitations and luciferase reporter-based transfection assays, CHOP was found to up-regulate SERPINA1 cooperating with c-JUN, which was previously shown to up-regulate SERPINA1, thus aggravating hepatic accumulation of ATZ. Increased CHOP levels were detected in diseased livers of children homozygous for the Z allele. In summary, CHOP and c-JUN up-regulate SERPINA1 transcription and play an important role in hepatic disease by increasing the burden of proteotoxic ATZ, particularly in the pediatric population.

MIB2 variants altering NOTCH signalling result in left ventricle hypertrabeculation/non-compaction and are associated with Ménétrier-like gastropathy.

We performed whole exome sequencing in individuals from a family with autosomal dominant gastropathy resembling Ménétrier disease, a premalignant gastric disorder with epithelial hyperplasia and enhanced EGFR signalling. Ménétrier 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 Ménétrier-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 Ménétrier disease.

Down-regulation of hepatocyte nuclear factor-4α and defective zonation in livers expressing mutant Z α1-antitrypsin.

α1 -Antitrypsin (AAT) deficiency is one of the most common genetic disorders and the liver disease due to the Z mutant of AAT (ATZ) is a prototype of conformational disorder due to protein misfolding with consequent aberrant intermolecular protein aggregation. In the present study, we found that livers of PiZ transgenic mice expressing human ATZ have altered expression of a network of hepatocyte transcriptional factors, including hepatocyte nuclear factor-4α, that is early down-regulated and induces a transcriptional repression of ATZ expression. Reduced hepatocyte nuclear factor-4α was associated with activation of ß-catenin, which 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. Down-regulation of hepatocyte nuclear factor-4α expression and defective zonation in livers have not been recognized so far as features of the liver disease caused by ATZ and are likely involved in metabolic disturbances and in the increased risk of hepatocellular carcinoma in patients with AAT deficiency. CONCLUSION: The findings of this study are consistent with the concept that abnormal AAT protein conformation and intrahepatic accumulation have broad effects on metabolic liver functions. (Hepatology 2017;66:124-135).

SR-A and SREC-I are Kupffer and endothelial cell receptors for helper-dependent adenoviral vectors.

Helper-dependent adenoviral (HDAd) vectors can mediate long-term, high-level transgene expression from transduced hepatocytes with no chronic toxicity. However, a toxic acute response with potentially lethal consequences has hindered their clinical applications. Liver sinusoidal endothelial cells (LSECs) and Kupffer cells are major barriers to efficient hepatocyte transduction. Understanding the mechanisms of adenoviral vector uptake by non-parenchymal cells may allow the development of strategies aimed at overcoming these important barriers and to achieve preferential hepatocyte gene transfer with reduced toxicity. Scavenger receptors on Kupffer cells bind adenoviral particles and remove them from the circulation, thus preventing hepatocyte transduction. In the present study, we show that HDAd particles interact in vitro and in vivo with scavenger receptor-A (SR-A) and with scavenger receptor expressed on endothelial cells-I (SREC-I) and we exploited this knowledge to increase the efficiency of hepatocyte transduction by HDAd vectors in vivo through blocking of SR-A and SREC-I with specific fragments antigen-binding (Fabs).

Safe and effective liver-directed AAV-mediated homology-independent targeted integration in mouse models of inherited diseases.

Liver-directed adeno-associated viral (AAV) vector-mediated homology-independent targeted integration (AAV-HITI) by CRISPR-Cas9 at the highly transcribed albumin locus is under investigation to provide sustained transgene expression following neonatal treatment. We show that targeting the 3' end of the albumin locus results in productive integration in about 15% of mouse hepatocytes achieving therapeutic levels of systemic proteins in two mouse models of inherited diseases. We demonstrate that full-length HITI donor DNA is preferentially integrated upon nuclease cleavage and that, despite partial AAV genome integrations in the target locus, no gross chromosomal rearrangements or insertions/deletions at off-target sites are found. In line with this, no evidence of hepatocellular carcinoma is observed within the 1-year follow-up. Finally, AAV-HITI is effective at vector doses considered safe if directly translated to humans providing therapeutic efficacy in the adult liver in addition to newborn. Overall, our data support the development of this liver-directed AAV-based knockin strategy.

Balloon catheter delivery of helper-dependent adenoviral vector results in sustained, therapeutic hFIX expression in rhesus macaques.

Hemophilia B is an excellent candidate for gene therapy because low levels of factor IX (FIX) (≥1%) result in clinically significant improvement of the bleeding diathesis. Helper-dependent adenoviral (HDAd) vectors can mediate long-term transgene expression without chronic toxicity. To determine the potential for HDAd-mediated liver-directed hemophilia B gene therapy, we administered an HDAd expressing hFIX into rhesus macaques through a novel and minimally invasive balloon occlusion catheter-based method that permits preferential, high-efficiency hepatocyte transduction with low, subtoxic vector doses. Animals given 1 × 10(12) and 1 × 10(11) virus particle (vp)/kg achieved therapeutic hFIX levels for the entire observation period (up to 1,029 days). At 3 × 10(10) and 1 × 10(10) vp/kg, only subtherapeutic hFIX levels were achieved which were not sustained long-term. Balloon occlusion administration of HDAd was well tolerated with negligible toxicity. Five of six animals developed inhibitors to hFIX. These results provide important information in assessing the clinical utility of HDAd for hemophilia B gene therapy.

Genome editing without nucleases confers proliferative advantage to edited hepatocytes and corrects Wilson disease.

Application of classic liver-directed gene replacement strategies is limited in genetic diseases characterized by liver injury due to hepatocyte proliferation, resulting in decline of therapeutic transgene expression and potential genotoxic risk. Wilson disease (WD) is a life-threatening autosomal disorder of copper homeostasis caused by pathogenic variants in copper transporter ATP7B and characterized by toxic copper accumulation, resulting in severe liver and brain diseases. Genome editing holds promise for the treatment of WD; nevertheless, to rescue copper homeostasis, ATP7B function must be restored in at least 25% of the hepatocytes, which surpasses by far genome-editing correction rates. We applied a liver-directed, nuclease-free genome editing approach, based on adeno-associated viral vector-mediated (AAV-mediated) targeted integration of a promoterless mini-ATP7B cDNA into the albumin (Alb) locus. Administration of AAV-Alb-mini-ATP7B in 2 WD mouse models resulted in extensive liver repopulation by genome-edited hepatocytes holding a proliferative advantage over nonedited ones, and ameliorated liver injury and copper metabolism. Furthermore, combination of genome editing with a copper chelator, currently used for WD treatment, achieved greater disease improvement compared with chelation therapy alone. Nuclease-free genome editing provided therapeutic efficacy and may represent a safer and longer-lasting alternative to classic gene replacement strategies for WD.

Autosomal dominant Ménétrier-like disease.

BACKGROUND: Familial occurrence of Ménétrier disease is rare and has been reported only in few instances. METHODS: Affected patients from a large pedigree were evaluated at the clinical, endoscopic, and pathological levels. RESULTS: Affected members presented with gastropathy of variable severity but without protein loss. Endoscopy and pathology findings were consistent with Ménétrier disease; however, gastric transforming growth factor α (TGF-α) immunohistochemistry and real-time polymerase chain reaction showed no increase in TGF-α expression. CONCLUSIONS: We describe a unique, 4-generation pedigree with autosomal dominant gastropathy exhibiting the typical clinical, endoscopic, and pathological findings of Ménétrier-like disease, though in the absence of protein loss and with no increase in the levels of gastric TGF-α. Members of this family may be affected by a novel and previously unrecognised hereditary form of gastric hyperplasia.

Full-length ATP7B reconstituted through protein trans-splicing corrects Wilson disease in mice.

Wilson disease (WD) is a genetic disorder of copper homeostasis, caused by deficiency of the copper transporter ATP7B. Gene therapy with recombinant adeno-associated vectors (AAV) holds promises for WD treatment. However, the full-length human ATP7B gene exceeds the limited AAV cargo capacity, hampering the applicability of AAV in this disease context. To overcome this limitation, we designed a dual AAV vector approach using split intein technology. Split inteins catalyze seamless ligation of two separate polypeptides in a highly specific manner. We selected a DnaE intein from Nostoc punctiforme (Npu) that recognizes a specific tripeptide in the human ATP7B coding sequence. We generated two AAVs expressing either the 5'-half of a codon-optimized human ATP7B cDNA followed by the N-terminal Npu DnaE intein or the C-terminal Npu DnaE intein followed by the 3'-half of ATP7B cDNA, under the control of a liver-specific promoter. Intravenous co-injection of the two vectors in wild-type and Atp7b -/- mice resulted in efficient reconstitution of full-length ATP7B protein in the liver. Moreover, Atp7b -/- mice treated with intein-ATP7B vectors were protected from liver damage and showed improvements in copper homeostasis. Taken together, these data demonstrate the efficacy of split intein technology to drive the reconstitution of full-length human ATP7B and to rescue copper-mediated liver damage in Atp7b -/- mice, paving the way to the development of a new gene therapy approach for WD.

Liver-directed gene-based therapies for inborn errors of metabolism.

INTRODUCTION: Inborn errors of metabolism include several genetic disorders due to disruption of cellular biochemical reactions. Although individually rare, collectively they are a large and heterogenous group of diseases affecting a significant proportion of patients. Available treatments are often unsatisfactory. Liver-directed gene therapy has potential for treatment of several inborn errors of metabolism. While lentiviral vectors and lipid nanoparticle-mRNA have shown attractive features in preclinical studies and still have to be investigated in humans, adeno-associated virus (AAV) vectors have shown clinical success in both preclinical and clinical trials for in vivo liver-directed gene therapy. AREAS COVERED: In this review, we discussed the most relevant clinical applications and the challenges of liver-directed gene-based approaches for therapy of inborn errors of metabolism. EXPERT OPINION: Challenges and prospects of clinical gene therapy trials and preclinical studies that are believed to have the greatest potential for clinical translation are presented.

The growth hormone-insulin-like growth factor axis in glycogen storage disease type 1: evidence of different growth patterns and insulin-like growth factor levels in patients with glycogen storage disease type 1a and 1b.

OBJECTIVES: To investigate the growth hormone (GH)-insulin-like growth factor (IGF) system in patients with glycogen storage disease type 1 (GSD1). STUDY DESIGN: This was a prospective, case-control study. Ten patients with GSD1a and 7 patients with GSD1b who were given dietary treatment and 34 sex-, age-, body mass index-, and pubertal stage-matched control subjects entered the study. Auxological parameters were correlated with circulating GH, either at basal or after growth hormone releasing hormone plus arginine test, insulin-like growth factors (IGF-I and IGF-II), and anti-pituitary antibodies (APA). RESULTS: Short stature was detected in 10.0% of patients with GSD1a, 42.9% of patients with GSD1b (P = .02), and none of the control subjects. Serum IGF-I levels were lower in patients with GSD1b (P = .0001). An impaired GH secretion was found in 40% of patients with GSD1a (P = .008), 57.1% of patients with GSD1b (P = .006), and none of the control subjects. Short stature was demonstrated in 3 of 4 patients with GSD1b and GH deficiency. The prevalence of APA was significantly higher in patients with GSD1b than in patients with GSD1a (P = .02) and control subjects (P = .03). The GH response to the provocative test inversely correlated with the presence of APA (P = .003). Compared with levels in control subjects, serum IGF-II and insulin levels were higher in both groups of patients, in whom IGF-II levels directly correlated with height SD scores (P = .003). CONCLUSION: Patients with GSD1a have an impaired GH secretion associated with reference range serum IGF-I levels and normal stature, whereas in patients with GSD1b, the impaired GH secretion, probably because of the presence of APA, was associated with reduced IGF-I levels and increased prevalence of short stature. The increased IGF-II levels, probably caused by increased insulin levels, in patients with GSD1 are presumably responsible for the improved growth pattern observed in patients receiving strict dietary treatment.

Terminal osseous dysplasia with pigmentary defects (TODPD): Follow-up of the first reported family, characterization of the radiological phenotype, and refinement of the linkage region.

Terminal osseous dysplasia with pigmentary defects (TODPD) is an X-linked dominant syndrome with distal limb anomalies and pigmentary skin defects. We have previously described this syndrome in several females from a large, four-generation pedigree. The presentation in the affected patients included multiple anomalies, hypertelorism, iris colobomas, punched-out pigmentary abnormalities over the face and scalp, brachydactyly, and digital fibromatosis. The phenotype was highly variable thus suggesting that X-inactivation plays an important role in the expression of the disease. Following our initial description of this condition there have been reports of more cases supporting the initial phenotypic description of this disease. We report on the follow-up of this family at about 10 years from the first evaluation. A detailed clinical follow-up and a review of the skeletal surveys suggests that although the most striking features involves the hands and feet, the skeletal involvement is more generalized and affects many other areas. Our previous linkage analysis has demonstrated mapping to Xq27.3-Xq28. Using a 6,056 SNP array, we have further refined the critical region within the Xq28 region. We have also excluded two candidate genes (FLNA and FAM58A) mapping in the critical region. The identification of the gene responsible for this rare condition will shed light on the molecular pathways leading to the various congenital anomalies of TODPD and will allow a more accurate genetic counseling to the affected individuals.

Skin fibroblasts of patients with geleophysic dysplasia due to FBN1 mutations have lysosomal inclusions and losartan improves their microfibril deposition defect.

BACKGROUND: Geleophysic dysplasia (GPHYSD) is a disorder characterized by dysmorphic features, stiff joints and cardiac involvement due to defects of TGF-ß signaling. GPHYSD can be caused by mutations in FBN1, ADAMTLS2, and LTBP3 genes. METHODS AND RESULTS: Consistent with previous reports, we found intracellular inclusions of unknown material by electron microscopy (EM) in skin fibroblasts of two GPHYSD individuals carrying FBN1 mutations. Moreover, we found that the storage material is enclosed within lysosomes and is associated with the upregulation of several lysosomal genes. Treatment of GPHYSD fibroblasts carrying FBN1 mutations with the angiotensin II receptor type 1 inhibitor losartan that inhibits TGF-ß signaling did not reduce the storage but improved the extracellular deposition of fibrillin-1 microfibrils. CONCLUSION: Losartan is a promising candidate drug for treatment of GPHYSD due to FBN1 defects.

Geleophysic dysplasia: novel missense variants and insights into ADAMTSL2 intracellular trafficking.

Geleophysic dysplasia (GPHYSD1, MIM231050; GPHYSD2, MIM614185; GPHYSD3, MIM617809) is an autosomal disorder characterized by short-limb dwarfism, brachydactyly, cardiac valvular disease, and laryngotracheal stenosis. Mutations in ADAMTSL2, FBN1, and LTBP3 genes are responsible for this condition. We found that three previously described cases of GPHYSD diagnosed clinically were homozygote or compound heterozygotes for five ADAMTSL2 variants, four of which not being previously reported. By electron microscopy, skin fibroblasts available in one case homozygote for an ADAMTSL2 variant showed a defective intracellular localization of mutant ADAMTSL2 protein that did not accumulate within lysosome-like intra-cytoplasmic inclusions. Moreover, this mutant ADAMTSL2 protein was less secreted in medium and resulted in increased SMAD2 phosphorylation in transfected HEK293 cells.

Gene therapy for inherited diseases of liver metabolism.

Gene therapy is entering the stage of initial clinical development to treat a growing number of inherited metabolic diseases. This review outlines the development of liver-directed gene therapy for diseases caused by deficiencies of enzymes that are primarily expressed in the liver and discusses the disorders that appear most promising for clinical translation.

Challenges and Prospects for Helper-Dependent Adenoviral Vector-Mediated Gene Therapy.

Helper-dependent adenoviral (HDAd) vectors that are devoid of all viral coding sequences are promising non-integrating vectors for gene therapy because they efficiently transduce a variety of cell types in vivo, have a large cloning capacity, and drive long-term transgene expression without chronic toxicity. The main obstacle preventing clinical applications of HDAd vectors is the host innate inflammatory response against the vector capsid proteins that occurs shortly after intravascular vector administration and result in acute toxicity, the severity of which is dose dependent. Intense efforts have been focused on elucidating adenoviral vector-host interactions and the factors involved in the acute toxicity. This review focuses on the recent acquisition of data on such interactions and on strategies investigated to improve the therapeutic index of HDAd vectors.