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Distribution of the protein kinase C substrates MARCKS and MRP in the postnatal developing rat brain
1Department of Psychiatry, University of Florida College of Medicine, Gainesville 32610-0256, USA. rkm@mail.med.upenn.edu
Abstract:
The myristoylated alanine-rich C kinase substrate (MARCKS) and MARCKS-related protein (MRP) are both membrane-associated phosphoproteins that interact with calmodulin and filamentous actin in a protein kinase C phosphorylation-dependent manner. In the present study, we examined MARCKS and MRP gene expression in the postnatal (P) rat brain (1, 7, 14, 21, and 90 days after birth) by using quantitative in situ hybridization. At P1, MRP expression was high in neocortex, striatum, thalamus, cerebellar cortex, and hippocampus (CA1-CA3, hilus, and granule cell layer) but low in brainstem and, between P7 and P14, exhibited a dramatic decline in each of these regions except hippocampal CA1 and granule cell layers. Between P14 and P21, MRP expression increased in white matter regions including the corpus callosum, fimbria/fornix, and cerebellar deep white matter. At P90 (adult), MRP remained strongly expressed in the olfactory bulb, medial habenula, hippocampal CA1, and the inner two-thirds of granule cell layer, temporal, and entorhinal cortices, the corpus callosum and fimbria/fornix, and cerebellar white matter. At P1, MARCKS was strongly expressed in the majority of brain regions except the brainstem, which subsequently declined gradually to approximate adult levels by P14. Between P14 and P21, MARCKS expression declined gradually in the hilus, remained elevated in hippocampal CA1, CA3, and granule cell layers, and increased dramatically in the corpus callosum and fimbria/fornix. At P90, MARCKS expression declined in hippocampal CA3 and hilus and remained strongly expressed in hippocampal CA1 and granule cell layers, regions of the olfactory bulb, the medial habenula, temporal cortex, and cerebellar granule and Purkinje cells. Expression of both MARCKS and MRP in regions undergoing neuronal proliferation, migration, and neurite outgrowth suggest a common role in these developmental events, whereas differences in expression during development and in the adult brain provide evidence of differential regulation.
Insights
Myristoylated alanine-rich C kinase substrate (MARCKS) and MARCKS-related protein (MRP) show distinct developmental expression patterns in the rat brain. Their varied gene expression suggests both common and unique roles in brain development and adult function.
Area of Science:
- Neuroscience
- Developmental Biology
- Molecular Biology
Background:
- Myristoylated alanine-rich C kinase substrate (MARCKS) and MARCKS-related protein (MRP) are key membrane-associated phosphoproteins.
- Both proteins interact with calmodulin and filamentous actin in a protein kinase C phosphorylation-dependent manner.
- Understanding their developmental expression is crucial for elucidating their roles in brain formation and function.
Purpose of the Study:
- To investigate the spatiotemporal gene expression patterns of MARCKS and MRP in the postnatal rat brain.
- To identify developmental stages and brain regions with significant expression changes for both proteins.
- To explore potential common and differential roles of MARCKS and MRP in brain development.
Main Methods:
- Quantitative in situ hybridization was employed to analyze gene expression.
- Expression levels were examined across multiple postnatal time points: P1, P7, P14, P21, and P90 (adult).
- Specific brain regions including the neocortex, hippocampus, cerebellum, and white matter tracts were analyzed.
Main Results:
- MRP expression was initially high in many regions, declining significantly by P7-P14, with notable increases in white matter by P14-P21.
- MARCKS expression was widespread at P1, gradually declining to adult levels by P14, with specific increases in white matter by P14-P21.
- Both proteins showed distinct adult expression profiles, with MARCKS and MRP persisting in specific neuronal populations and white matter tracts.
Conclusions:
- The differential expression of MARCKS and MRP during postnatal development suggests distinct regulatory mechanisms.
- Co-expression in areas of active neuronal proliferation, migration, and neurite outgrowth indicates a common role in these developmental processes.
- Distinct expression patterns in the adult brain highlight specialized functions for MARCKS and MRP beyond development.