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Identification of tuberous sclerosis 2 messenger RNA splice variants that are conserved and differentially expressed
1Division of Medical Science, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
Abstract:
Tuberous sclerosis 2 (Tsc2) gene is the target of a germline insertion in the Eker rat model of inherited cancer susceptibility. This tumor suppressor gene, when mutated, gives rise to a spectrum of epithelial and nonepithelial neoplasms in the rat, as well as multisystem involvement of hamartomas in the human. In this study, we characterized the rat Tsc2 cDNA and found that it is highly homologous with the human gene, including a conserved rap1GAP catalytic domain. Sequence analysis of independent rat clones from a kidney cDNA library revealed distinct but related variants of the Tsc2 transcripts stemming from alternative splicing involving two noncontiguous exons within the translated region. The first of these, located at amino acids 947 to 990, gives rise to isoforms with or without the 129-bp exon. There exists another variant related to the use of a "cryptic" splice acceptor site in the downstream exon that results in an in-frame 3-bp deletion. A separate 69-bp exon encoding a novel serine-rich amino acid sequence (1272 to 1295) was also alternatively spliced. Together, we have found a minimum of four and potentially eight Tsc2 isoforms that are differentially expressed in a tissue-specific manner. These splice variants are highly conserved in the human gene, suggesting a possible functional role of these Tsc2 isoforms in various cell regulatory and developmental processes.
Insights
The Tuberous sclerosis 2 (Tsc2) gene in Eker rats, a model for inherited cancer, exhibits alternative splicing. This generates multiple Tsc2 isoforms with potential roles in cell regulation and development.
Area of Science:
- Genetics
- Molecular Biology
- Cancer Research
Background:
- The Tuberous sclerosis 2 (Tsc2) gene is implicated in inherited cancer susceptibility, as demonstrated by germline insertion in the Eker rat model.
- Mutations in this tumor suppressor gene lead to various neoplasms in rats and hamartomas in humans.
Purpose of the Study:
- To characterize the rat Tsc2 cDNA and identify alternative splicing variants.
- To investigate the homology between rat and human Tsc2 genes and their functional implications.
Main Methods:
- Sequence analysis of rat Tsc2 cDNA clones from a kidney library.
- Identification and characterization of alternatively spliced transcripts and their encoded protein domains.
Main Results:
- Rat Tsc2 cDNA is highly homologous to human Tsc2, including a conserved rap1GAP catalytic domain.
- Alternative splicing of Tsc2 transcripts results in isoforms with variations in exon inclusion/exclusion and cryptic splice site usage.
- A minimum of four and potentially eight differentially expressed Tsc2 isoforms were identified in a tissue-specific manner.
Conclusions:
- The identified Tsc2 splice variants are conserved in humans, suggesting a significant functional role.
- These Tsc2 isoforms likely play roles in diverse cell regulatory and developmental processes.