Vesicular transport involves SNARE (soluble- N-ethylmaleimide-sensitive-factor-attachment-protein-receptor) proteins on transport vesicles and on target membranes. Syntaxin 13 is a SNARE enriched in brain, associated with recycling endosomes; its overexpression in PC12 cells promotes neurite outgrowth. This suggests an important role for receptor recycling during neuronal differentiation. Here we describe the spatiotemporal pattern of syntaxin 13 expression during mouse brain development. During early embryogenesis (E12-E15), it was found in the forebrain ventricular zone and in primary motor and sensory neurons in the brainstem, spinal cord and sensory ganglia. In the forebrain at E15, syntaxin 13 was not detected in neuroblasts in the intermediate zone of the embryonic hemispheric wall, while there was labeling in cortical neurons in deeper layers starting at E15-18, and progressively in later-generated neurons up to layer II around P6. Syntaxin 13 reached maximal expression in all brain divisions at about P7, followed by a decrease, with heterogeneous neuron populations displaying various staining intensities in adult brain. While usually restricted to the soma of neurons, we transiently detected syntaxin 13 in dendrites of pyramidal neurons during the first postnatal week. In conclusion, the developmentally regulated syntaxin 13 expression in various neuronal populations is consistent with its involvement in endocytic trafficking and neurite outgrowth.
"In addition, its expression is enriched in brain and overexpression enhances neurite outgrowth in NGF-stimulated PC12 cells [Hirling et al., 2000]. Interestingly, syntaxin 13 and the sr-PLPs share a striking similarity in their subcellular localization as well as in both their spatial and temporal patterns of expression during development [Sarria, 2002]. The similarities in expression profile suggest that the sr-isoforms may play a role in vesicular transport in neurons comparable to that identified in OLs [Bongarzone et al., 2001]. "
[Show abstract][Hide abstract] ABSTRACT: The myelin proteolipid gene encodes two sets of proteins, the classic PLP and DM20 and the sr (soma-restricted)-PLP and sr-DM20. Unlike the classic proteolipids, the sr-products are expressed in both neurons and oligodendrocytes (OLs) and are not components of the myelin sheath. In OLs, the sr-isoforms are associated with endosomes and recycling vesicles indicating a possible nonmyelin function for these proteins. In this study, a purified antibody specific for the sr-products was used to examine the expression of these proteins during the development of the mouse brain. We found that while sr-PLP and sr-DM20 are expressed in OLs, the highest levels of immunoreactivity were found in neuronal populations. During early embryonic development (E13-E15), sr-proteolipids were detected in the dorsal root ganglion and motor neurons in the spinal cord. By E17, immunostaining for sr-PLP and sr-DM20 in the brain increased dramatically. The highest levels of immunoreactivity were found during the first and second weeks postnatal after which staining intensity declined to adult levels and the pattern of expression was more restricted. Robust staining persisted in many neuronal populations including nuclei in the hindbrain, Purkinje and granule neurons in the cerebellum, pyramidal cells in the cortex and mitral cells in the olfactory bulb. The spatial and temporal pattern of sr-PLP and sr-DM20 expression is very similar to that of the endosomal protein, syntaxin 13, consistent with the finding that the sr-PLPs may play a role in vesicular transport in neurons.
"This finding is probably due to a substitution of syntaxin 3 by another syntaxin isoform. A possible candidate is syntaxin 13, which was shown to be important for axon elongation and growth cone expansion in other systems (Hirling et al. 2000; Sarria et al. 2002). Late ontogenetic expression of syntaxin has also been reported in the pineal gland, which is a retina-related tissue (Redecker 2000). "
[Show abstract][Hide abstract] ABSTRACT: In the present study, we generated a systematic overview of the expression pattern and assembly profile of synaptic membrane proteins in ribbon synapses of the developing mouse retina. Using indirect immunofluorescence microscopy, we analyzed the spatial and temporal distribution of 11 important membrane and membrane-associated synaptic proteins (syntaxin 1/3, SNAP-25, synaptobrevin 2, synaptogyrin, synaptotagmin I, SV2A, SV2B, Rab3A, clathrin light chains, CSP and neuroligin I) during synaptogenesis. The temporospatial distribution of these synaptic proteins was "normalized" by the simultaneous visualization of the synaptic vesicle protein synaptophysin, which served as an internal reference protein. We found that expression of various synaptic membrane proteins started at different time points and changed progressively during development. At early stages of development synaptic vesicle membrane proteins at extrasynaptic locations did not always colocalize with synaptophysin, indicating that these proteins probably do not reside in the same transport vesicles. Despite a non-synchronized onset of protein expression, clustering and colocalization of all synaptic membrane proteins at ribbon synapses roughly occurred in the same time window (between day 4 after birth, P4, and P5). Thus, the basic synaptic membrane machinery is already present in ribbon synapses before the well-known complete morphological maturation of ribbon synapses between P7 and P12. We conclude that ribbon synapse formation is a multistep process in which the concerted recruitment of synaptic membrane proteins is a relatively early event and clearly not the final step.
Cell and Tissue Research 03/2003; 311(2):159-73. DOI:10.1007/s00441-002-0674-0 · 3.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Genetic strains of mice represent an important resource for research on the biological determinants of complex diseases and behavioral phenotypes. To date, the approaches used have had little success in identifying causal genes. We have evaluated brain gene expression in C57BL/6J (B6) and DBA/2J (D2) inbred mouse strains using differential display to identify a number of sequences showing significant expression differences between the two strains. These differences were confirmed by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR. Knowing that B6 and D2 mouse strains differ for a number of behavioral phenotypes, we asked whether this difference in brain gene expression could explain any of these traits. Here, we show that the expression of two of these genes, retinaldehyde binding protein 1 (Rlbp1) and syntaxin 12 (Stx12), co-segregate with the ethanol preference phenotype in a B6D2 F2 population. Our results suggest a potential role for Rlbp1 and Stx12 in ethanol preference in mice, a conclusion supported by the location of these genes in quantitative trait loci (QTL) regions for this phenotype. This experimental approach has the potential for a broad application in the assessment of the roles of differentially expressed genes in a variety of complex phenotypes, with the advantage of identifying novel and potentially causal candidate genes directly.
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