title: Hepatic fibrinogen storage disease: identification of two novel mutations (p.Asp316Asn, fibrinogen Pisa and p.Gly366Ser, fibrinogen Beograd) impacting on the fibrinogen γ-module.
abstract: BACKGROUND
  Quantitative fibrinogen deficiencies (hypofibrinogenemia and afibrinogenemia) are rare congenital disorders characterized by low/unmeasurable plasma fibrinogen antigen levels. Their genetic basis is invariably represented by mutations within the fibrinogen genes (FGA, FGB and FGG coding for the Aα, Bβ and γ chains). Currently, only four mutations (p.Gly284Arg, p.Arg375Trp, delGVYYQ 346-350, p.Thr314Pro), all affecting the fibrinogen γ chain, have been reported to cause fibrinogen storage disease (FSD), a disorder characterized by protein aggregation, endoplasmic reticulum retention and hypofibrinogenemia.
  
  
  OBJECTIVE
  To investigate the genetic basis of FSD in two hypofibrinogenemic patients.
  
  
  METHODS
  The mutational screening of the fibrinogen genes was performed by direct DNA sequencing. The impact of identified mutations on fibrinogen structure was investigated by in-silico molecular modeling. Liver histology was evaluated by light microscopy, electron microscopy and immunocytochemistry.
  
  
  RESULTS
  Here, we describe two hypofibrinogenemic children with persistent abnormal liver function parameters. Direct sequencing of the coding portion of fibrinogen genes disclosed two novel FGG missense variants (p.Asp316Asn, fibrinogen Pisa; p.Gly366Ser, fibrinogen Beograd), both present in the heterozygous state and affecting residues located in the fibrinogen C-terminal γ-module. Liver sections derived from biopsies of the two patients were examined by immunocytochemical analyses, revealing hepatocyte cytoplasmic inclusions immunoreactive to anti-fibrinogen antibodies.
  
  
  CONCLUSIONS
  Our work strongly confirms the clustering of mutations causing FSD in the fibrinogen γ chain between residues 284 and 375. Based on an in-depth structural analysis of all FSD-causing mutations and on their resemblance to mutations leading to serpinopathies, we also comment on a possible mechanism explaining fibrinogen polymerization within hepatocytes.
authors.affiliation: Department of Biomedical Sciences, Humanitas University, Rozzano, Milan, Italy.|Humanitas Clinical and Research Center, Rozzano, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Asselta
authors.affiliation: Department of Biomedical Sciences, Humanitas University, Rozzano, Milan, Italy.|Humanitas Clinical and Research Center, Rozzano, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Robusto
authors.affiliation: Pathology Department, S. Paolo Hospital, Milan, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Braidotti
authors.affiliation: Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy.|Angelo Bianchi Bonomi Haemophilia and Thrombosis Centre, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico and Luigi Villa Foundation, Milan, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Peyvandi
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Pediatric Gastroenterology, University Hospital Santa Chiara, Pisa, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Nastasio
authors.affiliation: Paediatric Liver, GI and Transplantation, Azienda Ospedaliera Papa Giovanni XXIII, Bergamo, Italy.
authors.forename: L
authors.initials: L
authors.lastname: D'Antiga
authors.affiliation: Department of Gastroenterology and Hepatology, University Children's Hospital, Belgrade, Serbia.
authors.forename: V N
authors.initials: VN
authors.lastname: Perisic
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Pediatric Gastroenterology, University Hospital Santa Chiara, Pisa, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Maggiore
authors.affiliation: Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, Università degli Studi di Milano, Segrate, Milan, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Caccia
authors.affiliation: Department of Biomedical Sciences, Humanitas University, Rozzano, Milan, Italy.|Humanitas Clinical and Research Center, Rozzano, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Duga
mesh_terms: D000347:Afibrinogenemia / Q000175:diagnosis / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D005260:Female; D005340:Fibrinogen / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015241:Fibrinogens, Abnormal / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D020022:Genetic Predisposition to Disease; D006579:Heterozygote; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008107:Liver Diseases / Q000175:diagnosis / Q000235:genetics* / Q000378:metabolism; D008111:Liver Function Tests; D008297:Male; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010641:Phenotype; D011487:Protein Conformation; D013329:Structure-Activity Relationship
chemical_list: D015241:Fibrinogens, Abnormal; C000608150:fibrinogen Beograd; C000608149:fibrinogen Pisa; C027539:fibrinopeptides gamma; D005340:Fibrinogen
keywords: congenital; fibrinogen; hypofibrinogenemia; immunocytochemistry; liver diseases; missense mutation