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Identification of a complete Cek7 receptor protein tyrosine kinase coding sequence and cDNAs of alternatively spliced
1Department of Microbiology and Immunology, Pennsylvania State University, College of Medicine, Hershey 17033.
Abstract:
Receptor protein tyrosine kinases (RPTK) are critical components of signal transduction pathways in multicellular organisms. Identification of new RPTK constitutes an initial step in understanding the variety of signalling pathways in which these proteins participate. In this study, a cDNA containing a complete coding sequence for Cek7 (chicken RPTK) has been cloned from a chicken embryo expression library using anti-phosphotyrosine antibodies (Ab). Cek7 is a member of the EPH (human RPTK) subfamily of RPTK; this subfamily is characterized by extracellular domains containing an immunoglobulin-like motif, a Cys-rich region and two fibronectin type-III repeats. Analysis of additional cDNAs revealed that two positions of alternative splicing in primary transcripts may produce several isoforms of this RPTK; cDNAs corresponding to three isoforms of this receptor are reported. These isoforms are predicted to have altered extracellular ligand-binding domains and/or altered cytoplasmic juxtamembrane regions. The nucleotide sequence of cek7 cDNAs identified in this study diverges at the 3' end from the sequence found in a recently described partial cek7 cDNA [Sajjadi and Pasquale, Oncogene 8 (1993) 1807-1813]. Therefore, a third position of alternative splicing may produce Cek7 RPTK with divergent C-terminal tails. RNA blot analysis revealed expression of this receptor at highest levels in the central nervous system and eyes of 10-day-old chicken embryos.
Insights
Researchers identified the complete coding sequence for chicken Cek7 receptor protein tyrosine kinase (RPTK). This discovery aids in understanding diverse signaling pathways involving RPTKs and their isoforms.
Area of Science:
- Molecular Biology
- Cell Signaling
- Developmental Biology
Background:
- Receptor protein tyrosine kinases (RPTKs) are crucial for signal transduction in multicellular organisms.
- Identifying novel RPTKs is essential for mapping diverse cellular signaling pathways.
Purpose of the Study:
- To clone and characterize the complete coding sequence of Cek7, a chicken RPTK.
- To investigate potential isoforms of Cek7 arising from alternative splicing.
Main Methods:
- Cloning of Cek7 cDNA from a chicken embryo expression library using anti-phosphotyrosine antibodies.
- Analysis of additional cDNAs to identify alternative splicing events.
- RNA blot analysis to determine Cek7 expression patterns.
Main Results:
- The complete coding sequence for chicken Cek7 (a member of the EPH subfamily) was successfully cloned.
- Evidence suggests at least three isoforms of Cek7 exist due to alternative splicing, potentially affecting ligand-binding and juxtamembrane domains.
- Cek7 expression is highest in the central nervous system and eyes of 10-day-old chicken embryos.
Conclusions:
- The study provides a comprehensive characterization of the Cek7 RPTK, including its isoforms.
- Alternative splicing generates Cek7 variants with potentially distinct functional properties.
- High expression in the nervous system and eyes suggests a significant role for Cek7 in these tissues during embryonic development.