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Differential expression of the cellular src gene during vertebrate development
Abstract:
Cellular genes that are homologous to the transforming genes of certain RNA tumor viruses are suspected to play a functional role during normal developmental processes. To investigate this further, we are studying the expression of the cellular homolog of the Rous sarcoma virus transforming gene (c-src) during embryogenesis of fish, frog, and chicken by quantitative determination of the activity of the c-src encoded protein kinase (pp60c-src). The kinase activity from embryos of fish, frog, and chicken displays the same enzymatic characteristics as the kinase from adult animals: It phosphorylates only tyrosine residues in protein substrates, and its activity is relatively insensitive to inhibition by the diadenosine nucleotide Ap4A. During the course of development, the varying kinase activity level reflects differential expression of the c-src gene product. The kinase activity is low during early development, increases dramatically during organogenesis, and decreases thereafter to the level found in adult animals. The kinase activity displays an organ specificity, with brain showing the highest activity in embryos as well as in adults. Muscle, however, shows high activities during organogenesis, but no or barely detectable activity in adult animals. Our data suggest, therefore, that the c-src gene product plays more of a role in differentiation than in proliferation processes during embryogenesis, and that it may act as a pleiotropic effector.
Insights
The cellular src (c-src) gene product, pp60c-src, shows dynamic expression during embryogenesis, with highest activity in the brain and muscle during development, suggesting a role in differentiation.
Area of Science:
- Molecular Biology
- Developmental Biology
- Oncogenes
Background:
- Cellular homologs of viral transforming genes, like c-src, are implicated in normal development.
- Understanding c-src expression during embryogenesis is crucial for deciphering its developmental roles.
Purpose of the Study:
- To investigate the expression and activity of the c-src gene product (pp60c-src) during embryogenesis in fish, frog, and chicken.
- To determine the enzymatic characteristics and developmental regulation of pp60c-src kinase activity.
Main Methods:
- Quantitative determination of pp60c-src protein kinase activity in embryonic and adult tissues.
- Analysis of enzymatic properties, including substrate specificity and inhibitor sensitivity.
- Comparison of kinase activity across different developmental stages and organs.
Main Results:
- Embryonic pp60c-src kinase activity exhibited similar enzymatic characteristics to adult forms, phosphorylating tyrosine residues and being insensitive to Ap4A.
- Kinase activity levels varied significantly during development, increasing during organogenesis and declining thereafter.
- Brain consistently showed the highest activity, while muscle exhibited high activity during organogenesis but diminished in adults.
Conclusions:
- The c-src gene product is differentially expressed during embryogenesis, with activity levels correlating with developmental stages.
- pp60c-src likely plays a more significant role in differentiation than proliferation during embryogenesis.
- The c-src gene product may function as a pleiotropic effector in developmental processes.