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A family of fibronectin mRNAs in human normal and transformed cells
Abstract:
Previously, two fibronectin mRNAs, generated by alternative splicing of the extra domain (ED) and type III connecting segments (IIICS) sequences, have been described in a human transformed cell line and in human liver, respectively. We now report on a family of fibronectin mRNAs identified by Northern blotting analysis in two normal human fibroblast strains (HEL 299 and Flow 7000) and five transformed cell lines (8387 and HT-1080, fibrosarcomas; G-361, melanoma; JEG-3, choriocarcinoma; and RD, rhabdomyosarcoma). Seven different fibronectin mRNA forms with electrophoretic mobilities ranging between 8.6 and 7.7 kb were identified. Each cell line contains three (HEL 299, Flow 7000 and 8387) or two (HT-1080, G-361, JEG-3 and RD) fibronectin mRNAs species with characteristic size. In all cell lines we detected one fibronectin mRNA form which lacks the ED sequence (ED- fibronectin mRNA) and one or two fibronectin mRNAs containing it (ED+ fibronectin mRNA). These data show that the presence of ED+ and ED- fibronectin mRNAs is a general feature of all cells tested. Moreover, the fibronectin mRNA pattern is characteristic of the cell type analyzed, suggesting the occurrence of specifically programmed splicing mechanisms in each cell line.
Insights
Researchers identified multiple fibronectin messenger RNA (mRNA) forms in normal and transformed human cells. The presence of extra domain (ED) positive and negative fibronectin mRNA variants is common across cell types, with specific patterns indicating cell-type-programmed splicing.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Alternative splicing of fibronectin mRNA generates different protein isoforms.
- Previous studies identified two fibronectin mRNA variants in specific human cell types.
Purpose of the Study:
- To investigate the diversity of fibronectin mRNA forms in various human cell lines.
- To determine if the presence of extra domain (ED) containing fibronectin mRNA is universal.
- To explore cell-type-specific fibronectin mRNA expression patterns.
Main Methods:
- Northern blotting analysis was employed to detect and characterize fibronectin mRNA.
- Analysis was performed on two normal human fibroblast strains and five human transformed cell lines.
Main Results:
- Seven distinct fibronectin mRNA forms, ranging from 8.6 to 7.7 kilobases, were identified.
- All tested cell lines expressed fibronectin mRNA lacking the ED sequence (ED-) and containing the ED sequence (ED+).
- Each cell line exhibited a characteristic pattern of fibronectin mRNA species, with 2 or 3 distinct forms.
Conclusions:
- The expression of both ED+ and ED- fibronectin mRNAs is a general characteristic of human cells.
- Fibronectin mRNA profiles are cell-type-specific, suggesting regulated alternative splicing mechanisms.
- These findings highlight the complexity of fibronectin gene expression regulation.