CaM I mRNA is localized to apical dendrites during postnatal development of neurons in the rat brain

Abstract

In the rat, a single calmodulin (CaM) protein is encoded by three separate genes which produce five different transcripts. The significance of the multiple CaM genes is not known; however, individual CaM transcripts could be targeted to specific intracellular sites. In this report, the cellular distribution of CaM I mRNAs was analyzed in the postnatal rat brain. The 4.0‐kb CaM I transcript was present in neuronal cell bodies and also localized to apical dendritic processes. In cerebral cortical neurons, the 4.0‐kb CaM I mRNA was detected in apical dendrites at postnatal day (PD) 5 to 15. In hippocampal neurons, this CaM message was present in dendritic processes from PD 5 to 20, whereas in Purkinje neurons it was detected in dendrites at PD 15 and 20. The presence of the 4.0‐kb CaM I mRNA in dendrites of the rat brain supports the notion of targeting transcripts derived from the CaM multigene family to discrete intracellular destinations. © 1996 Wiley‐Liss, Inc.

Proteomic Analysis of Brain Plasma Membranes Isolated by Affinity Two-phase Partitioning

“…Ribosomal proteins represent a large fraction of the total protein mass of a cell, and their shear amount may explain their presence among the isolated proteins. An alternative explanation is provided by the existence of dendritic mRNA in cerebellar Purkinje cells, such as mRNA for calmodulin (41), inositol 1,4,5-trisphosphate receptor type 1 (42), and L7 (43). We conclude that the purified ribosomal proteins may be part of the dendritic translational machinery in the Purkinje cells, leading to their enclosure into the forming PM vesicles during tissue homogenization.…”

Multiple calmodulin mRNAs are selectively transported to functionally different neuronal and glial compartments in the rat hippocampus. An electron microscopic in situ hybridization study

“…There is evidence that newly synthesized mRNAs are preferentially transported to the postsynaptic zones of newly formed (Schacher et al, 1999) or recently activated synapses (Steward et al, 1998;Steward and Worley, 2001) or in the developing nervous tissue (Berry and Brown, 1996). In harmony with our previous results (Palfi et al, 1999), we established that the mRNAs corresponding to the three CaM genes are differentially targeted to the dendrites as the CaM I and CaM III mRNAs were more abundant than the CaM II transcript in this compartment.…”

“…Transcripts of the CaM I and II genes were found within neurite extensions, whereas the CaM III mRNAs predominated in the cell body. Berry and Brown (1996) detected a transient distribution of the 4.0 kb CaM I mRNA in the apical dendrites of pyramidal and Purkinje neurons during postnatal days 5-20 in the rat. Later, Palfi et al (1999) demonstrated that the CaM mRNAs are significantly more abundant in the molecular layers (areas consisting mainly of dendrites) than in the white matter areas (containing mostly axonal tracts) in the adult rat brain.…”

Protein Synthesis at Synaptic Sites on Dendrites

“…The dendritic localization of some mRNAs may be developmentally regulated. For example, the mRNA for calmodulin can be detected by in situ hybridization in dendritic laminae of developing, but not mature animals (Berry & Brown 1996). This is consistent with the idea that local dendritic protein synthesis is especially important during periods of synaptogenesis (Palacios-Pru et al 1981Steward & Falk 1986).…”