Fibrinogen angers with a new deletion (γ GVYYQ 346‐350) causes hypofibrinogenemia with hepatic storage

Abstract

To cite this article: Dib N, Quelin F, Ternisien C, Hanss M, Michalak S, de Mazancourt P, Rousselet MC, Calè s P. Fibrinogen angers with a new deletion Summary. Introduction: This study reports a family with chronically abnormal blood liver function tests (LFT) and congenital hypofibrinogenemia. The proposita had cirrhosis initially related to alcohol abuse and chronic viral hepatitis C (HCV), but abnormal LFT persisted even when alcohol intake was stopped and despite HCV treatment was efficient based on serum RNA negative testing. Results: Needle biopsy specimens of the proposita and her brother showed eosinophilic intracytoplasmic inclusions that reacted strongly with fibrinogen antisera on direct immunofluorescence. Electron microscopic examination showed that the rough endoplasmic reticulum was filled with inclusions that consisted of densely packed, curved tubular structures arranged in a fingerprint-like pattern. Coagulation studies revealed low functional and antigenic fibrinogen concentrations suggestive of hypofibrinogenemia. Amplification and DNA sequencing showed a heterozygous deletion of the a7690 to g7704 nucleotides of the c chain gene in the 3¢end of exon 8 (g 7690_7704del14; Genbank access M10014); this deletion encompassed the splicing site at position 7703 and predicts in a new putative consensus splicing sequence (AATGgtatgtt). RNA was extracted from a liver specimen from the propositaÕs brother. The cDNA obtained by reverse transcription polymerase chain reaction confirmed the usage of a newly generated donor site at position 7688 of the genomic sequence resulting in an in-frame heterozygous 5 amino acid deletion p.G372_Q376del) and that this mutation is responsible for a new splicing site at position 7688 of the genomic sequence. Conclusion: we suggest that the molecular defect in fibrinogen Angers results in an impaired assembly and causes defective secretion and hepatic storage of fibrinogen.

γ375W fibrinogen-synthesizing CHO cells indicate the accumulation of variant fibrinogen within endoplasmic reticulum

“…These results demonstrated that assembled and non-secreted 375W fibrinogen was accumulated in the dilated ER and aggregated variant fibrinogen was seen as regularly structured fibular material, being similar to the fingerprint-like pattern observed at inclusion bodies in patients' hepatocytes affected with HERSD [10][11][12][13][14]. In addition to R375W mutation, G284R [8], T314P [9], and deletion of G346-Q350 [15], all mutations residing in the globular D domain, have been reported as HERSD with hypofibrinogenemia, and all also demonstrated the presence of hepatocellular cytoplasmic inclusion bodies filled with anti-fibrinogen antibody-reacting materials and were also observed as tubular materials with a 16 fingerprint-like pattern by electron microscopy [8,9,15]. ER accumulation of variant protein inducing liver cirrhosis (HERSD) was originally reported in a deficiency (homozygotes) of A1AT (G342K, Z-mutation) [17].…”

“…Another four identical variant fibrinogens also reported lower levels of plasma fibrinogen and were diagnosed as hypofibrinogenemia [11][12][13][14]. Overall, 15 considering the excretion pattern of 375W we conclude that our recombinant fibrinogen-producing system using CHO cells gives results similar to patients with hypofibrinogenemia.…”

“…Genetic abnormalities in patients with these diseases have been found in all three genes and identified as missense, nonsense, or frameshift mutations; splice-site abnormalities; or large deletions, as listed in the fibrinogen variant database [updated on 26/01/2012, http://site.geht.org/site/Pratiques-Professionnelles/Base-de-donnees-Fibrinogene/Base-d e-donnees/Base-de-donnees-des-variants-du-Fibrinogene_40_.html]. Some patients with only four variant types of hypofibrinogenemia, substitution of G284R [8], T314P [9], and R375W mutation [10][11][12][13][14], and deletion of G346-Q350 [15] (all numbered as mature protein without signal peptide) have been reported to show onset of liver disease in so-called hepatic ER storage disease (HERSD) [16] or fibrinogen storage disease, being in the same category as genetic deficiency of -1-antitrypsin (A1AT) (G342K, Z-mutation) [17].…”

Recombinant variant fibrinogens substituted at residues γ326Cys and γ339Cys demonstrated markedly impaired secretion of assembled fibrinogen

“…When protein breakdown occurs by this system, an endoplasmic reticulum storage disease (ERSD) might be induced. ERSD caused by the storage of variant fibrinogen has been reported in four families of heterozygous variant fibrinogens, γ 284G >R [20], γ375R>W [21,22]), and deletion of γ346-350 [23]). All of these patients showed no significant levels of the variant fibrinogen in plasma, namely, hypofibrinogenemia.…”

Unique de-novo mutation of fibrinogen gene in a Chinese girl with hypofibrinogenemia

“…Clinically, most patients with hypofibrinogenemia are asymptomatic, whereas several cases present with bleeding, thrombosis or spontaneous abortion [3][4][5]. Up to date, many mutational analyses have defined key residues that are essential for fibrinogen structure or function, providing insights into the pathological mechanisms responsible for hypofibrinogenemia [6][7][8].…”