Expression of m-Golsyn/Syntabulin gene during mouse brain development.

We recently isolated the cDNA for the mouse Golsyn/Syntabulin (m-Golsyn/Syntabulin) gene and mapped it to mouse chromosome 15B3.2 syntenic with human chromosome 8q23, on which a locus responsible for primary open-angle glaucoma had been located. In the present study, we examined the expression of m-Golsyn/Syntabulin protein in various regions of mouse brain and its developmental changes by use of anti-GOLSYN antibody. m-Golsyn/Syntabulin protein was detected in various brain regions at embryonic day 14 and throughout the postnatal stages. Furthermore, as the histogenesis and maturation of brain proceeded, strong expression of the protein became detectable in cells of the choroid plexus, piriform cortex, pyramidal cell layer, and Purkinje cell layer. In situ hybridization analysis of the mouse brain revealed that localization of the m-Golsyn/Syntabulin transcript was very similar to that of m-Golsyn/Syntabulin protein, confirming the high-level expression of the m-Golsyn/Syntabulin gene in the specific brain regions. High-level expression of m-Golsyn/Syntabulin protein was also observed in the ocular tissues including the ciliary body, which is known as a site for the production of aqueous humor. These results may indicate a significant role for this protein in neuronal cells and other types of cells such as those of the choroid plexus and ciliary body.

Molecular cloning of the m-Golsyn gene and its expression in the mouse brain.

The mouse ortholog of the human GOLSYN gene, termed the m-Golsyn gene, was isolated and mapped to the region on mouse chromosome 15B3.2 syntenic with human chromosome 8q23. Three mRNA species (type la, 1b, and type 2) were produced by use of alternative transcription initiation points and alternative splicing events. The type 1 mRNAs were expressed only in the brain, whereas the type 2 was detected in various tissues. m-Golsyn protein was expressed in various tissues including the brain. Immunohistochemical study of m-Golsyn protein showed its prominent expression in the neuronal cells in various regions of the brain and strong expression in the choroid plexus ependymal cells lining the ventricles. m-Golsyn protein was found to be homologous to syntaphilin, a regulator of synaptic vesicle exocytosis. These results indicate that the m-Golsyn protein may play an important role in intracellular protein transport in neuronal cells of the brain.

Dystrophin is a possible end-target of ischemic preconditioning against cardiomyocyte oncosis during the early phase of reperfusion.

OBJECTIVE: Dystrophin is a sarcolemmal membrane protein that prevents the myocyte from oncosis induced by physical stress. Because ischemic preconditioning (IPC) protects mitochondria and prevents oncosis during reperfusion, we hypothesized that dystrophin is an end-target of IPC distal to mitochondrial protection. METHODS AND RESULTS: Isolated rat hearts were subjected to 30 min ischemia followed by reperfusion. IPC was introduced by 3 cycles of 5 min ischemia and 5 min reperfusion. The loss of sarcolemmal dystrophin and myocardial ATP during ischemia was comparable between the control and the IPC heart. Similar changes in sarcolemmal dystrophin and myocardial ATP were observed when the heart was treated with 2,4-dinitrophenol (DNP), an uncoupler of mitochondrial respiration, or oligomycin, an inhibitor of mitochondrial F1F0-ATPase. However, the IPC heart increased sarcolemmal dystrophin during reperfusion associated with an increase in tetramethylrhodamine ethylester (TMRE) uptake, an indicator of mitochondrial membrane potential (DeltaPsim), and myocardial ATP and inhibited myocyte oncosis. The increase in myocardial ATP and relocalization of dystrophin to the sarcolemma mediated by IPC was inhibited by treatment with DNP or oligomycin during reperfusion. In vitro experiments demonstrated that mitochondria isolated from the ischemic IPC heart increased ATP generation and facilitated relocalization of dystrophin from the insoluble to the soluble fractions in a manner sensitive to DNP and oligomycin. CONCLUSIONS: These results suggest that enhanced relocalization of dystrophin to the sarcolemma during reperfusion may be a mechanistic link between IPC-mediated improvement of mitochondrial function and its protection against oncosis during the early phase of reperfusion.

Molecular cloning and characterization of gene for Golgi-localized syntaphilin-related protein on human chromosome 8q23.

Loci for several human genetic diseases including glaucoma have been mapped to q23 region on chromosome 8. We carried out homology search analysis of the genomic sequence of a bacterial artificial chromosome (BAC) clone, KB1590E11, on 8q23 region, and mapped a previously described cDNA, KIAA1472, to this BAC clone. In this study, we determined the complete genomic structure of the KIAA1472 gene and its expression in various tissues and cell lines. Four mRNA species (types 1a, 1b, 1c, and 2) were produced from this gene by use of alternative transcription start sites and alternative-splicing events. These mRNAs were expressed in various tissues, except for type 1a, which was found only in the brain. Further, type 1 mRNA could be translated into two protein isoforms with different N-terminal sequences; and type 2 mRNA, into another type of isoform. All three of these KIAA1472 gene products were localized in Golgi apparatus and contained a C-terminal hydrophobic segment characteristic of a transmembrane domain, thus indicating them to be Golgi membrane-bound proteins. Furthermore, these proteins were homologous to syntaphilin, a molecule involved in guiding vesicular transport. These results indicate that KIAA1472 gene products may play an important role in vesicular traffic in various tissues including the brain.