To examine the role of the fibrinogen ␥ chain in the assembly and secretion of this multichain protein, we synthesized a series of fibrinogen variants with truncated ␥ chains, terminating between residues ␥379 and the C-terminus, ␥411. The variant fibrinogens were synthesized from altered ␥-chain complementary DNAs in cultured Chinese hamster ovary cells. Immunoassays of the culture media demonstrated that only those variants with ␥ chain longer than 386 residues were secreted and that the concentration of fibrinogen decreased with the length of the ␥ chain, from 1.4 g/mL for normal fibrinogen to 0.39 g/mL for ␥ 387 fibrinogen. Immunoassays of cell lysates showed that all variant ␥ chains were synthesized, although the levels varied significantly. For variants longer than 386 residues, levels decreased with length but remained near normal. In contrast, expression of the 4 variants with 386 residues or less was about 20-fold reduced. Quantitative reverse transcription-polymerase chain reaction demonstrated that the ␥-chain messenger RNA level was independent from chain length. Western blot analyses showed that lysates expressing variants with 387 residues or more contained species comparable to the known intermediates in fibrinogen assembly, including half-molecules. For shorter variants, these intermediates were not evident. We conclude that residues near the C-terminus of the ␥ chain are essential for fibrinogen assembly, and more specifically, that ␥387 is critical. We propose that the loss of residue ␥387 destabilized the structure of ␥ chain, preventing assembly of ␣␥ and ␥ dimers, essential intermediates in the assembly of normal fibrinogen. IntroductionFibrinogen is a 340-kd plasma glycoprotein consisting of 2 copies of 3 polypeptide chains, A␣, B, and ␥, linked by an extensive network of 29 intrachain and interchain disulfide bonds. 1,2 A separate gene encodes each polypeptide chain. The 3 chains are synthesized, assembled into the 6-chain molecule, and secreted from hepatocytes into the plasma. Studies of fibrinogen expressed from the endogenous genes in human hepatocytes or from transfected complementary DNAs (cDNAs) in baby hamster kidney (BHK) cells have shown that assembly occurs through specific intermediates. 3,4 These intermediates, ␣␥ dimers, ␥ dimers, and ␣␥ half-molecules, all include the ␥ chain.Normal fibrinogen levels are 2 to 4 mg/mL in plasma. Hypofibrinogenemia or afibrinogenemia, defined as reduced or immeasurable levels of fibrinogen in plasma, can be hereditary. Although the first case of afibrinogenemia was reported in 1920, 5 the genetic basis of these abnormalities was first demonstrated in 1999. 6 Since that time, 26 different mutations have been identified in cases of afibrinogenemia or hypofibrinogenemia. [7][8][9][10][11][12][13][14][15][16][17][18][19] These mutations were found in all 3 genes, and include missense, nonsense, and frameshift mutations; splice-site abnormalities; and large deletions. Thus, fibrinogen deficiencies are associated with a variety of genetic chan...
The linear stability of the two-dimensional Taylor–Green vortices, which is a spatially periodic array of vortices, in rotating stratified fluids is investigated by local and modal stability analysis. Five types of instability appear in general: the pure hyperbolic instability, the strato-hyperbolic instability, the rotational-hyperbolic instability, the centrifugal instability and the elliptic instability. The condition for each instability and the estimate of the growth rate, which are useful in interpreting numerical results, are obtained in the framework of local stability analysis. Realizability of an instability is introduced to predict whether an unstable mode corresponding to an unstable region found in the local stability analysis exists at finite Reynolds numbers. In the absence of stratification, the pure hyperbolic instability is dominant for weak rotation; it is stabilized for strong rotation. For strong anti-cyclonic rotation, the elliptic instability or the centrifugal instability becomes dominant depending on the parameter values; further stronger rotation stabilizes both instabilities. For strong cyclonic rotation, the rotational-hyperbolic instability or the elliptic instability becomes dominant, although the growth rate is smaller than the anti-cyclonic cases. Strong stratification changes the stability properties. The strato-hyperbolic instability occurs for weak rotation. The rotational-hyperbolic instability and the elliptic instability are weakened under cyclonic rotation, while the latter survives and extends the unstable range under anti-cyclonic rotation. The pure hyperbolic instability and the centrifugal instability are less affected by stratification. The mode structures of each instability are in good agreement with the corresponding solution to local stability equations, confirming the physical mechanism of the instability.
Two siblings with typical features of the Cockayne syndrome were studied at autopsy. Many glomeruli revealed a paucity of capillary loops and had thickened capillary walls. Some glomeruli with advanced lesions showed collapse of the glomerular tufts or complete hyalinization. Atrophy of tubules and interstitial fibrosis were also observed. There were no significant arteriosclerotic changes in the vessels. Ultrastructural studies demonstrated thickened glomerular basement membranes with bends and folds. These histopathological findings are different to those previously reported with the exception of the 1966 report by Ohno and Hirooka.
A rare -thalassemia mutation at the splicing junction [namely, G→C in intervening sequence (IVS) I-1] was found in a Japanese family. The proband and his mother were heterozygous for the mutation. Analysis of mRNA extracted from the reticulocyte-rich fraction obtained from the proband's mother revealed that the mutant -globin gene did not produce any detectable, stable mRNA including exon 1 and exon 2, since the polymorphism in exon 1 on her mutant gene was not detected in the RT-PCR products. Am.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.