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The structure and expression of the FGF receptor-1 mRNA isoforms in rat tissues
1Department of Biological Chemistry, Kyoto University, Faculty of Pharmaceutical Sciences, Japan.
Abstract:
In this paper, we describe the structure of rat FGF receptor-1 mRNA isoforms and their expression in a variety of rat tissues. The rat FGFR-1 has the characteristics of FGFR-1 as well as mouse, human and chicken homologs. FGFR-1 mRNA was detectable in all the tissues examined by Northern analysis or polymerase chain reaction, indicating that FGFR-1 mRNA is widely expressed in rat tissues. The rat FGFR-1 mRNA has isoforms in both the extracellular and intracellular regions. The extracellular isoforms which have two or three immunoglobulin-like domains, are expressed almost equally in the tissues except for brain. However, the large form is a major form in the brain. Furthermore, in the brain, half of FGFR-1 mRNAs have the six nucleotides, which encode a potential serine-threonine kinase phosphorylation site in the intracellular juxta-membrane region, deleted. In contrast to the brain, the deletion isoform is a minor form in the other tissues. The tissue-specific expression of the isoforms indicates that they have different physiological functions. Although other isoforms of FGFR-1 mRNA in tumor cell lines have been reported, the isoforms were undetectable in all rat tissues examined, indicating the isoforms are products of abnormal alternative splicing in tumor cell lines.
Insights
This study details rat fibroblast growth factor receptor-1 (FGFR-1) mRNA structures and their tissue-specific expression. Isoforms vary, particularly in the brain, suggesting distinct physiological roles for FGFR-1.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Fibroblast Growth Factor Receptor-1 (FGFR-1) is crucial for cellular processes.
- Understanding FGFR-1 mRNA structure and expression is key to deciphering its functions.
- Previous studies identified FGFR-1 isoforms in tumor cells, but their presence in normal tissues was unclear.
Purpose of the Study:
- To characterize rat FGFR-1 mRNA isoforms.
- To investigate the tissue-specific expression patterns of these isoforms.
- To differentiate normal FGFR-1 splicing from aberrant splicing in tumor cells.
Main Methods:
- Northern blot analysis to detect FGFR-1 mRNA.
- Polymerase chain reaction (PCR) to amplify and identify FGFR-1 mRNA sequences.
- Comparative analysis of FGFR-1 mRNA structures across different rat tissues.
Main Results:
- FGFR-1 mRNA is widely expressed in all examined rat tissues.
- Rat FGFR-1 exhibits extracellular isoforms (2-3 immunoglobulin-like domains) with near-equal expression, except in the brain where a larger form predominates.
- A specific deletion isoform, lacking a kinase phosphorylation site, is prevalent in the brain but minor in other tissues.
- Tumor-specific isoforms were not detected in normal rat tissues.
Conclusions:
- Rat FGFR-1 mRNA exists in multiple isoforms with distinct tissue-specific expression patterns, especially in the brain.
- These variations suggest specialized physiological functions for different FGFR-1 isoforms.
- The absence of previously reported tumor-specific isoforms in normal tissues indicates they arise from abnormal splicing in cancer cells.