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Relative expression of the RET9 and RET51 isoforms in human pheochromocytomas
H Le Hir1, N Charlet-Berguerand, A Gimenez-Roqueplo
1Centre de G¿en¿etique Mol¿eculaire, Laboratoire associ¿e ¿a l'Universit¿e Pierre et Marie Curie, Gif-sur-Yvette, France.
Abstract:
Activating mutations of the RET oncogene cause the inheritance of multiple endocrine neoplasia type 2 (MEN2). The RET pre-mRNA is spliced into several transcripts coding for multiple isoforms, including Ret9 and Ret51. When harboring activating mutations in the cytoplasmic region, the Ret51 protein displays a higher in vitro transforming efficiency as compared to the corresponding Ret9 isoform. We investigated whether a more transforming isoform was preferentially expressed in MEN2 tumors as compared to normal tissues or sporadic pheochromocytomas. By quantitative RNases protection assays, we measured the absolute abundance of the 3' splice variants in pheochromocytomas and in normal tissues. The proportion of RET51 transcripts was highly dispersed between tumors and normal tissues. In familial tumors the proportion of RET51 transcripts was significantly larger (48.1%) than in sporadic tumors (36.75%). This result suggests that the preferential expression of the Ret51 protein isoform, even though moderate, is a growth advantage for MEN2 tumors.
Insights
Activating RET oncogene mutations cause MEN2. The study found higher Ret51 transcript levels in familial MEN2 tumors, suggesting this isoform offers a growth advantage for multiple endocrine neoplasia type 2.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Activating mutations in the RET oncogene are linked to multiple endocrine neoplasia type 2 (MEN2).
- The RET gene produces multiple mRNA isoforms, including Ret9 and Ret51, with Ret51 exhibiting higher in vitro transforming activity when mutated.
- Preferential expression of more transforming isoforms may contribute to tumor development.
Purpose of the Study:
- To investigate if the more transforming Ret51 protein isoform is preferentially expressed in MEN2 tumors compared to normal tissues or sporadic pheochromocytomas.
- To determine the relative abundance of Ret9 and Ret51 transcripts in different tumor types and normal tissues.
Main Methods:
- Quantitative RNase protection assays were employed to measure the absolute abundance of 3' RET splice variants.
- Analysis was performed on pheochromocytomas (familial MEN2 and sporadic) and normal tissues.
Main Results:
- The proportion of RET51 transcripts showed significant variability across all samples.
- Familial MEN2 tumors exhibited a significantly higher proportion of RET51 transcripts (48.1%) compared to sporadic tumors (36.75%).
Conclusions:
- Preferential expression of the Ret51 isoform, although moderate, appears to provide a growth advantage in MEN2 tumors.
- This finding highlights the potential role of alternative splicing in the pathogenesis of multiple endocrine neoplasia type 2.