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Activated RET oncogene products induce maturation of xenopus oocytes
D Grieco1, M Santoro, N A Dathan
1Institute of Cancer Research, Columbia University, New York, New York 10032, USA.
Abstract:
The RET proto-oncogene encodes a transmembrane receptor of the tyrosine kinase family, recently found to be the gene responsible for the multiple endocrine neoplasia type 2A and 2B syndromes. RET was found specifically activated, by gene rearrangement, in human thyroid carcinomas of the papillary subtype. In most cases the activation consisted of an in frame fusion of the RET tyrosine-kinase domain, at the carboxy-terminus, with heterologous genes at the amino-terminus. These chimeric oncogenes are collectively named RET/PTC. Two forms of these gene products, RET/PTC1 and RET/PTC3, have been tested for their ability to induce meiotic maturation in Xenopus oocytes. Injection of RET/PTC mRNAs into immature oocytes induced maturation-promoting-factor (MPF) activation and germinal vesicle breakdown (GVBD). The injected oocytes expressed polypeptides recognized by an anti-RET gene product antibody as well as by an antiphosphotyrosine antibody, indicating activation of the tyrosine-kinase domain. The RET/PTC induced maturation was dependent on endogenous ras; in fact, the coinjection of RET/PTC mRNA with a neutralizing anti-ras antibody blocked oocytes maturation without interfering with the accumulation and tyrosine-phosphorylation of the RET/PTC protein.
Insights
The RET proto-oncogene, altered in thyroid cancer, activates cell maturation in Xenopus oocytes. This process requires Ras signaling, highlighting a key pathway in cell development and disease.
Area of Science:
- Oncology
- Molecular Biology
- Cell Signaling
Background:
- The RET proto-oncogene encodes a tyrosine kinase receptor implicated in Multiple Endocrine Neoplasia types 2A and 2B.
- RET gene rearrangements activate RET/PTC chimeric oncogenes in papillary thyroid carcinomas.
- The functional consequences of RET/PTC activation in cellular processes are not fully understood.
Purpose of the Study:
- To investigate the functional role of RET/PTC oncogenes in cellular development.
- To determine if RET/PTC can induce meiotic maturation in Xenopus oocytes.
- To elucidate the signaling pathways involved in RET/PTC-mediated oocyte maturation.
Main Methods:
- Injection of RET/PTC1 and RET/PTC3 messenger RNAs (mRNAs) into immature Xenopus oocytes.
- Assay for maturation-promoting-factor (MPF) activation and germinal vesicle breakdown (GVBD).
- Western blot analysis using anti-RET and anti-phosphotyrosine antibodies; assessment of Ras dependency via anti-Ras antibody coinjection.
Main Results:
- RET/PTC mRNA injection induced oocyte maturation, indicated by MPF activation and GVBD.
- Activated RET/PTC proteins were detected, confirming tyrosine kinase domain activity.
- Oocyte maturation induced by RET/PTC was dependent on endogenous Ras signaling, as blocking Ras inhibited maturation.
Conclusions:
- RET/PTC oncogenes can induce meiotic maturation in Xenopus oocytes.
- The tyrosine kinase activity of RET/PTC is essential for this effect.
- Ras signaling is a critical downstream pathway mediating RET/PTC-induced oocyte maturation.