Hepatic fibrinogen storage disease due to the fibrinogen γ375 Arg → Trp mutation "fibrinogen Aguadilla" is present in Arabs

Protein Misfolding and Aggregation: The Relatedness between Parkinson's Disease and Hepatic Endoplasmic Reticulum Storage Disorders

Dysfunction of cellular homeostasis can lead to misfolding of proteins thus acquiring conformations prone to polymerization into pathological aggregates. This process is associated with several disorders, including neurodegenerative diseases, such as Parkinson’s disease (PD), and endoplasmic reticulum storage disorders (ERSDs), like alpha-1-antitrypsin deficiency (AATD) and hereditary hypofibrinogenemia with hepatic storage (HHHS). Given the shared pathophysiological mechanisms involved in such conditions, it is necessary to deepen our understanding of the basic principles of misfolding and aggregation akin to these diseases which, although heterogeneous in symptomatology, present similarities that could lead to potential mutual treatments. Here, we review: (i) the pathological bases leading to misfolding and aggregation of proteins involved in PD, AATD, and HHHS: alpha-synuclein, alpha-1-antitrypsin, and fibrinogen, respectively, (ii) the evidence linking each protein aggregation to the stress mechanisms occurring in the endoplasmic reticulum (ER) of each pathology, (iii) a comparison of the mechanisms related to dysfunction of proteostasis and regulation of homeostasis between the diseases (such as the unfolded protein response and/or autophagy), (iv) and clinical perspectives regarding possible common treatments focused on improving the defensive responses to protein aggregation for diseases as different as PD, and ERSDs.

Hepatic and Extrahepatic Sources and Manifestations in Endoplasmic Reticulum Storage Diseases

Alpha-1-antitrypsin (AAT) and fibrinogen are secretory acute phase reactant proteins. Circulating AAT and fibrinogen are synthesized exclusively in the liver. Mutations in the encoding genes result in conformational abnormalities of the two molecules that aggregate within the rough endoplasmic reticulum (RER) instead of being regularly exported. That results in AAT-deficiency (AATD) and in hereditary hypofibrinogenemia with hepatic storage (HHHS). The association of plasma deficiency and liver storage identifies a new group of pathologies: endoplasmic reticulum storage disease (ERSD).

Hereditary Hypofibrinogenemia with Hepatic Storage

Fibrinogen is a 340-kDa plasma glycoprotein constituted by two sets of symmetrical trimers, each formed by the Aα, Bβ, and γ chains (respectively coded by the FGA, FGB, and FGG genes). Quantitative fibrinogen deficiencies (hypofibrinogenemia, afibrinogenemia) are rare congenital disorders characterized by low or unmeasurable plasma fibrinogen antigen levels. Their genetic basis is represented by mutations within the fibrinogen genes. To date, only eight mutations, all affecting a small region of the fibrinogen γ chain, have been reported to cause hereditary hypofibrinogenemia with hepatic storage (HHHS), a disorder characterized by protein aggregation in the endoplasmic reticulum, hypofibrinogenemia, and liver disease of variable severity. Here, we will briefly review the clinic characteristics of HHHS patients and the histological feature of their hepatic inclusions, and we will focus on the molecular genetic basis of this peculiar type of coagulopathy.

Structural Characteristics in the γ Chain Variants Associated with Fibrinogen Storage Disease Suggest the Underlying Pathogenic Mechanism

Particular fibrinogen γ chain mutations occurring in the γ-module induce changes that hamper γ-γ dimerization and provoke intracellular aggregation of the mutant fibrinogen, defective export and plasma deficiency. The hepatic storage predisposes to the development of liver disease. This condition has been termed hereditary hypofibrinogenemia with hepatic storage (HHHS). So far, seven of such mutations in the fibrinogen γ chain have been detected. We are reporting on an additional mutation occurring in a 3.5-year-old Turkish child undergoing a needle liver biopsy because of the concomitance of transaminase elevation of unknown origin and low plasma fibrinogen level. The liver biopsy showed an intra-hepatocytic storage of fibrinogen. The molecular analysis of the three fibrinogen genes revealed a mutation (Fibrinogen Trabzon Thr371Ile) at exon 9 of the γ chain in the child and his father, while the mother and the brother were normal. Fibrinogen Trabzon represents a new fibrinogen γ chain mutation fulfilling the criteria for HHHS. Its occurrence in a Turkish child confirms that HHHS can present in early childhood and provides relevant epidemiological information on the worldwide distribution of the fibrinogen γ chain mutations causing this disease. By analyzing fibrinogen crystal structures and calculating the folding free energy change (ΔΔG) to infer how the variants can affect the conformation and function, we propose a mechanism for the intracellular aggregation of Fibrinogen Trabzon and other γ-module mutations causing HHHS.

Rethinking fibrinogen storage disease of the liver: ground glass and globular inclusions do not represent a congenital metabolic disorder but acquired collective retention of proteins

Three types of intracytoplasmic inclusions immunoreactive to fibrinogen are collectively diagnosed as hepatic fibrinogen storage disease. This study aimed to better characterize ground glass (type II) and globular (type III) fibrinogen inclusions by the pathological examination of 3 cases and a literature review. Three adults (age: 32-64 years; male/female = 2:1) were unexpectedly found to have fibrinogen-positive ground glass changes (type II inclusions) by liver needle biopsy, against a background of acute hepatitis E, resolving acute cholangitis, or severe lobular hepatitis of unknown etiology. One patient also had fibrinogen-positive intracytoplasmic globules (type III inclusions) in the first biopsy, but they were not present in a second biopsy. None had coagulation abnormalities or hypofibrinogenemia. On immunostaining, both inclusions were strongly positive for not only fibrinogen but also C-reactive protein and C4d. Ultrastructurally, ground glass changes corresponded to membrane-bound cytoplasmic inclusions containing amorphous, granular material. The pathological features of type II fibrinogen inclusions were identical to those of pale bodies in hepatocellular carcinoma. The literature review suggested that type I fibrinogen inclusions characterized by a polygonal appearance are strongly associated with mutations in fibrinogen genes, coagulopathy, and family history, whereas type II/III inclusions are immunoreactive to multiple proteins and typically develop in cases of other unrelated liver diseases. In conclusion, type II and III fibrinogen inclusions do not represent a true hereditary storage disease but instead the collective retention of multiple proteins. Given the lack of clinical significance, a less specific name (e.g., pale body) may be more appropriate for those inclusions.

Hepatic fibrinogen storage disease and hypofibrinogenemia caused by fibrinogen Aguadilla mutation: a case report

Hepatic fibrinogen storage disease is a rare autosomal dominant genetic disorder characterized by hypofibrinogenemia, as well as the retention of variant fibrinogen within the hepatocellular endoplasmic reticulum. Here, we describe an asymptomatic 4-year-old boy with abnormal liver function test results and unexpected hypofibrinogenemia. Liver biopsy showed circular eosinophil inclusion bodies in the hepato-cytoplasm. Immunostaining results of eosinophil inclusion bodies were positive for fibrinogen. Following pretreatment with diastase, the inclusion bodies failed to stain with the periodic acid–Schiff technique; moreover, immunostaining results were positive for fibrinogen, but negative for alpha-1-antitrypsin. Genetic analysis identified a heterozygous missense mutation c.1201C > T (p. Arg401Trp) within the fibrinogen γ-chain (FGG) gene and an additional single nucleotide polymorphism c.-58 A > G within the 5′-untranslated region of the fibrinogen Aα-chain (FGA) gene. Thus, the patient was diagnosed with hepatic fibrinogen storage disease. Our results indicate that, for patients who exhibit chronic liver disease with unexpected hypofibrinogenemia, hepatic fibrinogen storage disease should be considered in the differential diagnosis. Moreover, our findings emphasize the importance of molecular diagnosis in patients with cryptogenic liver disease.

Clinical Consequences and Molecular Bases of Low Fibrinogen Levels

The study of inherited fibrinogen disorders, characterized by extensive allelic heterogeneity, allows the association of defined mutations with specific defects providing significant insight into the location of functionally important sites in fibrinogen and fibrin. Since the identification of the first causative mutation for congenital afibrinogenemia, studies have elucidated the underlying molecular pathophysiology of numerous causative mutations leading to fibrinogen deficiency, developed cell-based and animal models to study human fibrinogen disorders, and further explored the clinical consequences of absent, low, or dysfunctional fibrinogen. Since qualitative disorders are addressed by another review in this special issue, this review will focus on quantitative disorders and will discuss their diagnosis, clinical features, molecular bases, and introduce new models to study the phenotypic consequences of fibrinogen deficiency.

Fibrinogen Gamma Chain Mutations Provoke Fibrinogen and Apolipoprotein B Plasma Deficiency and Liver Storage

p.R375W (Fibrinogen Aguadilla) is one out of seven identified mutations (Brescia, Aguadilla, Angers, Al du Pont, Pisa, Beograd, and Ankara) causing hepatic storage of the mutant fibrinogen γ. The Aguadilla mutation has been reported in children from the Caribbean, Europe, Japan, Saudi Arabia, Turkey, and China. All reported children presented with a variable degree of histologically proven chronic liver disease and low plasma fibrinogen levels. In addition, one Japanese and one Turkish child had concomitant hypo-APOB-lipoproteinemia of unknown origin. We report here on an additional child from Turkey with hypofibrinogenemia due to the Aguadilla mutation, massive hepatic storage of the mutant protein, and severe hypo-APOB-lipoproteinemia. The liver biopsy of the patient was studied by light microscopy, electron microscopy (EM), and immunohistochemistry. The investigation included the DNA sequencing of the three fibrinogen and APOB-lipoprotein regulatory genes and the analysis of the encoded protein structures. Six additional Fibrinogen Storage Disease (FSD) patients with either the Aguadilla, Ankara, or Brescia mutations were investigated with the same methodology. A molecular analysis revealed the fibrinogen gamma p.R375W mutation (Aguadilla) but no changes in the APOB and MTTP genes. APOB and MTTP genes showed no abnormalities in the other study cases. Light microscopy and EM studies of liver tissue samples from the child led to the demonstration of the simultaneous accumulation of both fibrinogen and APOB in the same inclusions. Interestingly enough, APOB-containing lipid droplets were entrapped within the fibrinogen inclusions in the hepatocytic Endoplasmic Reticulum (ER). Similar histological, immunohistochemical, EM, and molecular genetics findings were found in the other six FSD cases associated with the Aguadilla, as well as with the Ankara and Brescia mutations. The simultaneous retention of fibrinogen and APOB-lipoproteins in FSD can be detected in routinely stained histological sections. The analysis of protein structures unraveled the pathomorphogenesis of this unexpected phenomenon. Fibrinogen gamma chain mutations provoke conformational changes in the region of the globular domain involved in the "end-to-end" interaction, thus impairing the D-dimer formation. Each monomeric fibrinogen gamma chain is left with an abnormal exposure of hydrophobic patches that become available for interactions with APOB and lipids, causing their intracellular retention and impairment of export as a secondary unavoidable phenomenon.

The fibrous form of intracellular inclusion bodies in recombinant variant fibrinogen-producing cells is specific to the hepatic fibrinogen storage disease-inducible variant fibrinogen

Fibrinogen storage disease (FSD) is a rare disorder that is characterized by the accumulation of fibrinogen in hepatocytes and induces liver injury. Six mutations in the γC domain (γG284R, γT314P, γD316N, the deletion of γG346-Q350, γG366S, and γR375W) have been identified for FSD. Our group previously established γ375W fibrinogen-producing Chinese hamster ovary (CHO) cells and observed aberrant large granular and fibrous forms of intracellular inclusion bodies. The aim of this study was to investigate whether fibrous intracellular inclusion bodies are specific to FSD-inducible variant fibrinogen. Thirteen expression vectors encoding the variant γ-chain were stably or transiently transfected into CHO cells expressing normal fibrinogen Aα- and Bβ-chains or HuH-7 cells, which were then immunofluorescently stained. Six CHO and HuH-7 cell lines that transiently produced FSD-inducible variant fibrinogen presented the fibrous (3.2-22.7 and 2.1-24.5%, respectively) and large granular (5.4-25.5 and 7.7-23.9%) forms of intracellular inclusion bodies. Seven CHO and HuH-7 cell lines that transiently produced FSD-non-inducible variant fibrinogen only exhibit the large granular form. These results demonstrate that transiently transfected variant fibrinogen-producing CHO cells and inclusion bodies of the fibrous form may be useful in non-invasive screening for FSD risk factors for FSD before its onset.

Fibrinogen storage disease in a Chinese boy with de novo fibrinogen Aguadilla mutation: Incomplete response to carbamazepine and ursodeoxycholic acid

Background

Fibrinogen storage disease (FSD) is a rare autosomal-dominant disorder caused by mutation in FGG, encoding the fibrinogen gamma chain. Here we report the first Han Chinese patient with FSD, caused by de novo fibrinogen Aguadilla mutation, and his response to pharmacologic management.

Case presentation

Epistaxis and persistent clinical-biochemistry test-result abnormalities prompted liver biopsy in a boy, with molecular study of FGG in him and his parents. He was treated with the autophagy enhancer carbamazepine, reportedly effective in FSD, and with ursodeoxycholic acid thereafter. Inclusion bodies in hepatocellular cytoplasm stained immune-histochemically for fibrinogen. Selective analysis of FGG found the heterozygous mutation c.1201C > T (p.Arg401Trp), absent in both parents. Over more than one year’s follow-up, transaminase and gamma-glutamyl transpeptidase activities have lessened but not normalized.

Conclusion

This report expands the epidemiology of FSD and demonstrates idiosyncrasy in response to oral carbamazepine and/or ursodeoxycholic acid in FSD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-016-0507-3) contains supplementary material, which is available to authorized users.

Fibrinogen storage disease and cirrhosis associated with hypobetalipoproteinemia owing to fibrinogen Aguadilla in a Turkish child

BACKGROUND AND AIMS

Fibrinogen gene mutations can rarely result in hepatic fibrinogen storage disease (HFSD). Herein, we report on the first Turkish family carrying the mutation p.Arg375Trp (fibrinogen Aguadilla) in the γ-chain of the fibrinogen (FGG) gene.

METHODS

Clinical, laboratory and histopathological findings of the patient were documented. Molecular study of fibrinogen gene was performed in the patient and her family members.

RESULTS

The proband was 5 years old girl presenting with advanced liver fibrosis of unknown origin. The child had very low plasma levels of fibrinogen and hypobetalipoproteinemia. Immunomorphologic and electron microscopic studies showed selective and exclusive accumulation of fibrinogen within the endoplasmic reticulum in liver biopsy of the patient. Patient, mother, two sisters and one brother carried p.Arg375Trp mutation (fibrinogen Aguadilla) in FGG gene. The patient was treated with ursodeoxycholic acid and carbamazepine. After 3 months, carbamazepine was suspended upon family decision and unresponsiveness of carbamazepine.

CONCLUSIONS

HFSD is characterized by hypofibrinogenemia and accumulation of abnormal fibrinogen within hepatocytes. In addition, hypofibrinogenemia is associated with hypobetalipoproteinemia in Aguadilla mutation.

Hypofibrinogenemia and liver disease: a new case of Aguadilla fibrinogen and review of the literature

INTRODUCTION

Fibrinogen storage disease (FSD) is characterized by hypofibrinogenemia and hepatic inclusions due to impaired release of mutant fibrinogen which accumulates and aggregates in the hepatocellular endoplasmic reticulum. Liver disease is variable.

AIM

We studied a new Swiss family with fibrinogen Aguadilla. In order to understand the molecular peculiarity of FSD mutations, fibrinogen Aguadilla and the three other causative mutations, all located in the γD domain, were modelled.

METHOD

The proband is a Swiss girl aged 4 investigated because of fatigue and elevated liver enzymes. Protein structure models were prepared using the Swiss-PdbViewer and POV-Ray software.

RESULTS

The proband was found to be heterozygous for fibrinogen Aguadilla: FGG Arg375Trp. Familial screening revealed that her mother and maternal grandmother were also affected and, in addition, respectively heterozygous and homozygous for the hereditary haemochromatosis mutation HFE C282Y. Models of backbone and side-chain interactions for fibrinogen Aguadilla in a 10-angstrom region revealed the loss of five H-bonds and the gain of one H-bond between structurally important amino acids. The structure predicted for fibrinogen Angers showed a novel helical structure in place of hole 'a' on the outer edge of γD likely to have a negative impact on fibrinogen assembly and secretion.

CONCLUSION

The mechanism by which FSD mutations generate hepatic intracellular inclusions is still not clearly established although the promotion of aberrant intermolecular strand insertions is emerging as a likely cause. Reporting new cases is essential in the light of novel opportunities of treatment offered by increasing knowledge of the degradation pathway and autophagy.