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Differential expression of MEK1 and MEK2 during mouse development
A Alessandrini1, B K Brott, R L Erikson
1Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Abstract:
Map/Erk kinase 1 (MEK1) and MEK2 activate the Erk/ MAP kinases and have been implicated in cell growth and differentiation. To investigate the role of MEKs during mouse development, we have examined their expression and activity in various murine tissues during embryonic development and in the adult mouse. MEK2 RNA message is expressed at high levels in all embryonic tissues examined, including all neural tissues, and liver. This can be observed by in situ hybridization of tissue sections of 14.5-day-old mouse embryos, as well as by Northern blot analyses. MEK1, on the other hand, is expressed at very low levels in most embryonic murine tissue but can be detected in developing skeletal muscle. It is expressed at higher levels in adult tissue, particularly in brain, where it is expressed at high levels. Western blot analyses of MEK1 and MEK2 in 14.5-day-old embryonic and adult mouse tissue confirm the RNA analysis. Levels of MEK1 kinase activity are particularly high in adult brain tissues as well. These findings suggest that MEK2 may be the primary Erk/MAP kinase activator during development and that MEK1 may play a role in the proliferative or mitogenic response in adult mouse tissues. This study also raises the possibility that MEK1 and MEK2 might not have redundant functions in cells but may possess unique specificity in their interactions with upstream activators or downstream targets.
Insights
Map/Erk kinase 2 (MEK2) is crucial for embryonic development, while Map/Erk kinase 1 (MEK1) is more active in adult tissues, suggesting distinct roles in cell signaling.
Area of Science:
- Molecular Biology
- Developmental Biology
- Cell Signaling
Background:
- Map/Erk kinase 1 (MEK1) and MEK2 are key activators of Erk/MAP kinases, involved in cell growth and differentiation.
- Understanding the specific roles of MEK1 and MEK2 in development and adult physiology is essential.
Purpose of the Study:
- To investigate the expression and activity of MEK1 and MEK2 in various murine tissues during embryonic development and in adulthood.
- To elucidate the distinct functions of MEK1 and MEK2 in cellular processes.
Main Methods:
- In situ hybridization and Northern blot analyses to examine MEK RNA expression in embryonic and adult mouse tissues.
- Western blot analyses to assess MEK1 and MEK2 protein levels and kinase activity.
- Analysis of tissues from 14.5-day-old mouse embryos and adult mice.
Main Results:
- MEK2 RNA message is highly expressed in all examined embryonic tissues, including neural tissues and liver.
- MEK1 expression is low in most embryonic tissues but detectable in skeletal muscle, with higher levels in adult brain.
- Western blot analysis confirmed RNA expression patterns, with high MEK1 kinase activity observed in adult brain tissue.
Conclusions:
- MEK2 likely serves as the primary Erk/MAP kinase activator during mouse development.
- MEK1 may play a significant role in proliferative or mitogenic responses in adult mouse tissues.
- MEK1 and MEK2 may possess unique, non-redundant functions rather than overlapping roles.