Fibronectin mRNA splice variant in articular cartilage lacks bases encoding the V, III-15, and I-10 protein segments.
Fibronectin is an extracellular matrix glycoprotein encoded by a single gene. Alternative RNA splicing has been reported at three sites, ED (extra type III domain)-A, ED-B, and the variable or V region. Articular cartilage fibronectin monomers are rarely (ED-A)+, but approximately 25% are (ED-B)+. RNA gel electrophoresis and Northern blot analysis identified two (ED-B)+ and two (ED-B)- fibronectin transcripts in cartilage, each pair differing by approximately 750 bases. This difference results from a previously unreported RNA splicing pattern that eliminates not only the V region but also nucleotides encoding protein segments III-15 and I-10. This new splice variant, which we designate (V+C)-, represents the majority of fibronectin transcripts in equine, canine, and rabbit articular cartilage but is absent in the liver. Reverse transcriptase-polymerase chain reaction analyses of 11 additional equine tissues failed to detect the (V+C)- splice variant, except for very low levels in lymph node, bone, aorta, and skin. Furthermore, chondrocytes grown in monolayer culture maintain high levels of fibronectin expression but stop expressing (V+C)- transcripts over time. The tissue-specific expression pattern of this novel fibronectin isoform suggests that it may have an important function in the matrix organization of cartilage.
MacLeod
J N
JN
Department of Physiology, James A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA.
Burton-Wurster
N
N
Gu
D N
DN
Lust
G
G
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002358:Cartilage, Articular / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D004285:Dogs; D005353:Fibronectins / Q000737:chemistry / Q000235:genetics*; D014644:Genetic Variation; D006736:Horses; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D011817:Rabbits; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
D017931:DNA Primers; D018076:DNA, Complementary; D005353:Fibronectins; D012333:RNA, Messenger