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Objective: Ameloblastoma has a high risk of bone invasion and local recurrence. However, the mechanisms of bone invasion in ameloblastoma remain unclear. In this study, we established an experimental model for matrix metalloproteinase (MMP) induction and osteoclastogenesis using ameloblastoma-derived cells. Study design: We established an ameloblastoma-derived cell line without viral genes and analyzed the expression of all Wnt and Frizzled members and MMPs by real-time reverse transcription-polymerase chain reaction, and analyzed the activity of MMP-2 and MMP-9 by the in-gel-gelatinase assay. Results: AM-3, newly established ameloblastoma-derived cells retained the morphology of primary-cultured ameloblastoma cells. AM-3 cells overexpressed the messenger RNA of Wnt-5a, Frizzled-2, MMP-2, and MMP-9 and showed the potential of osteoclastogenesis. In addition, Wnt-3a-treatment induced expression and activation of MMP-9 in AM-3 cells. Conclusions: Our study suggests that AM-3 cells retained the characteristics of ameloblastoma, without acquiring typical features of cancer cells. Furthermore, Wnt signaling induced MMP-9 in ameloblastoma cells. [ABSTRACT FROM AUTHOR]

Citrin is the liver-type mitochondrial aspartate-glutamate carrier that participates in urea, protein, and nucleotide biosynthetic pathways by supplying aspartate from mitochondria to the cytosol.Citrin also plays a role in transporting cytosolic NADH reducing equivalents into mitochondria as a component of the malate-aspartate shuttle. In humans, loss-of-function mutations in the SLC25A13 gene encoding citrin cause both adult-onset type II citrullinemia and neonatal intrahepatic cholestasis, collectively referred to as human citrin deficiency. Citrin knock-out mice fail to display features of human citrin deficiency. Based on the hypothesis that an enhanced glycerol phosphate shuttle activity may be compensating for the loss of citrin function in the mouse, we have generated mice with a combined disruption of the genes for citrin and mitochondrial glycerol 3-phosphate dehydrogenase. The resulting double knock-out mice demonstrated citrullinemia, hyperammonemia that was further elevated by oral sucrose administration, hypoglycemia, and a fatty liver, all features of human citrin deficiency. An increased hepatic lactate/pyruvate ratio in the double knock-out mice compared with controls was also further elevated by the oral sucrose administration, suggesting that an altered cytosolic NADH/NAD+ ratio is closely associated with the hyperammonemia observed. Microarray analyses identified over 100 genes that were differentially expressed in the double knock-out mice compared with wild-type controls, revealing genes potentially involved in compensatory or downstream effects of the combined mutations. Together, our data indicate that the more severe phenotype present in the citrin/mitochondrial glycerol-3-phosphate dehydrogenase double knock-out mice represents a more accurate model of human citrin deficiency than citrin knock-out mice. [ABSTRACT FROM AUTHOR]

Ca2+ regulation of the Ca2+ binding mitochondrial carriers for aspartate/glutamate (AGCs) is provided by their N-terminal extensions, which face the intermembrane space. The two mammalian AGCs, aralar and citrin, are members of the malate-aspartare NADH shuttle. We report that their N-terminal extensions contain up to four pairs of EF-hand motifs plus a single vestigial EF-hand, and have no known homolog. Aralar and citrin contain one fully canonical EF-hand pair and aralar two additional half-pairs, in which a single EF-hand is predicted to bind Ca2+. Shuttle activity in brain or skeletal muscle mitochondria, which contain aralar as the major AGC, is activated by Ca2+ with S0.5 values of 280-350 n; higher than those obtained in liver mitochondria (100-150 n) that contain citrin as the major AGC. We have used aralar- and citrin-deficient mice to study the role of the two isoforms in heart, which expresses both AGCs. The S0.5 for Ca2+ activation of the shuttle in heart mitochondria is about 300 n, and it remains essentially unchanged in citrin-deficient mice, although it undergoes a drastic reduction to about 100 n in aralar-deficient mice. Therefore, aralar and citrin, when expressed as single isoforms in heart, confer differences in Ca2+ activation of shuttle activity, probably associated with their structural differences. In addition, the results reveal that the two AGCs fully account for shuttle activity in mouse heart mitochondria and that no other glutamate transporter can replace the AGCs in this pathway. [ABSTRACT FROM AUTHOR]

Abstract: We found reduced locomotor activity (LA) under fasting in systemic carnitine-deficient juvenile visceral steatosis (jvs −/−) mice. When food was withdrawn at 8:00a.m. (lights-off at 7:00p.m., 12h/cycle), the nocturnal LA of jvs −/− mice was much less than the control (jvs +/+ and jvs +/−) mice. LA recovered under carnitine or sucrose administration, but not under medium-chain triglyceride. In addition, fasted jvs −/− mice, without any energy supply, were activated by modafinil, a stimulator of the dopamine pathway. These results suggest that the reduced LA is not adequately explained by energy deficit. As the fasted jvs −/− mice showed lower body core temperature (BT), we examined the central nervous system regulating LA and BT. We found lower percentage of c-Fos positive orexin neurons in the lateral hypothalamus and reduced orexin-A concentration in the cerebrospinal fluid of fasted jvs −/− mice. Sleep analysis revealed that fasted jvs −/− mice had disruption of prolonged wakefulness, with a higher frequency of brief episodes of non-REM sleep during the dark period than fasted jvs +/+ mice. These results strongly suggest that the reduced LA in fasted jvs −/− mice is related to the inhibition of orexin neuronal activity. [Copyright &y& Elsevier]

Aralar is a mitochondrial calcium-regulated aspartate-glutamate carrier mainly distributed in brain and skeletal muscle, involved in the transport of aspartate from mitochondria to cytosol, and in the transfer of cytosolic reducing equivalents into mitochondria as a member of the malate-aspartate NADH shuttle. In the present study, we describe the characteristics of aralar-deficient (Aralar-/-) mice, generated by a gene-trap method, showing no aralar mRNA and protein, and no detectable malate-aspartate shuttle activity in skeletal muscle and brain mitochondria. Aralar-/- mice were growth-retarded, exhibited generalized tremoring, and had pronounced motor coordination defects along with an impaired myelination in the central nervous system. Analysis of lipid components showed a marked decrease in the myelin lipid galactosyl cerebroside. The content of the myelin lipid precursor, N-acetylaspartate, and that of aspartate are drastically decreased in the brain of Aralar-/- mice. The defect in N-acetylaspartate production was also observed in cell extracts from primary neuronal cultures derived from Aralar-/- mouse embryos. These results show that aralar plays an important role in myelin formation by providing aspartate for the synthesis of N-acetylaspartate in neuronal cells. [ABSTRACT FROM AUTHOR]

To clarify the pathogenesis of cardiac hypertrophy in carnitine-deficient juvenile visceral steatosis (JVS) mice, we performed differential mRNA display analysis with the ventricles of control and JVS mice. We found a novel up-regulated gene, designated as carnitine deficiency-associated gene expressed in ventricle (CDV)-3. Northern blot analysis with a cDNA probe derived from the novel gene revealed two substantial mRNA species of prominent 4.1- and faint 3.5-kb in examined tissues of control and JVS mice. In spite of their widely expressed features, up-regulation of the gene was found predominantly in the ventricles and slightly in the auricles and skeletal muscles of JVS mice. The up-regulation of CDV-3 gene in the ventricles of JVS mice was significantly relieved by carnitine administration within 6 h. The entire cDNA nucleotide sequences showed that two kinds of cDNA, long and short versions (CDV-3A and -3B), corresponding to the detected mRNAs, are different in a 711 base fragment. Analysis of genomic DNA revealed that the two mRNAs were derived from a single CDV-3 gene with five exons by alternative splicing. The deduced amino acid sequences indicated that the isoforms consist of 236 and 281 residues, differing at regions near the carboxy-terminus but sharing 231 residues of the amino-terminal regions. A BLAST search revealed that they show a high similarity to a human predicted nuclear protein (H41), which has been reported to be up-regulated in breast cancer cells overexpressing cellular-erythroblastosis B-2 (c-erbB-2, a kind of tyrosine kinase).We report the identification and characterization of novel transcripts that may be involved in the development of cardiac hypertrophy caused by carnitine deficiency. [Copyright &y& Elsevier]

The present report describes the expression profiles of different tissues and developmental changes of mouse aspartate/glutamate carrier (AGC) genes, Slc25a13 and Slc25a12, and an ornithine transporter gene, Ornt1, in relation to urea cycle enzyme genes, carbamoylphosphate synthetase I (CPS) and argininosuccinate synthetase (ASS). Slc25a13 encodes citrin, recently found to be deficient in adult-onset type II citrullinemia and to function as AGC together with its isoform and product of Slc25a12, aralar1. Citrin was broadly distributed, but mainly in the liver, kidney and heart. Aralar1 was expressed in diaphragm, skeletal muscle, heart, brain and kidney, but not in the liver. These distribution profiles are different from the restricted of Ornt1, ASS and CPS. Citrin, ASS, CPS and Ornt1 showed similar patterns of developmental changes in the liver and small intestine, where they play a role in urea and arginine synthesis. Dietary, hormonal and physical manipulations caused varied changes of CPS, ASS and Ornt1 in the liver, but the change of citrin was not so marked as that of the others. Analysis using RT-PCR and restriction enzyme digestion revealed that the ornithine transporter most expressed is Ornt1, although Ornt2 is detectable at a minute level. All these results suggest that citrin as AGC plays a role in urea synthesis as well as many fundamental metabolic pathways in the liver, and shares metabolic functions with aralar1 in other tissues, and that Ornt1 is an important component in urea synthesis in the liver and in arginine synthesis in the small intestine during the neonatal period. [Copyright &y& Elsevier]