Loss of deacetylation activity of Hdac6 affects emotional behavior in mice.

Acetylation is mediated by acetyltransferases and deacetylases, and occurs not only on histones but also on diverse proteins. Although histone acetylation in chromatin structure and transcription has been well studied, the biological roles of non-histone acetylation remain elusive. Histone deacetylase 6 (Hdac6), a member of the histone deacetylase (HDAC) family, is a unique deacetylase that localizes to cytoplasm and functions in many cellular events by deacetylating non-histone proteins including α-tubulin, Hsp90, and cortactin. Since robust expression of Hdac6 is observed in brain, it would be expected that Hdac6-mediated reversible acetylation plays essential roles in CNS. Here we demonstrate the crucial roles of Hdac6 deacetylase activity in the expression of emotional behavior in mice. We found that Hdac6-deficient mice exhibit hyperactivity, less anxiety, and antidepressant-like behavior in behavioral tests. Moreover, administration of Hdac6-specific inhibitor replicated antidepressant-like behavior in mice. In good agreement with behavioral phenotypes of Hdac6-deficient mice, Hdac6 dominantly localizes to the dorsal and median raphe nuclei, which are involved in emotional behaviors. These findings suggest that HDAC6-mediated reversible acetylation might contribute to maintain proper neuronal activity in serotonergic neurons, and also provide a new therapeutic target for depression.

Kbus/Idr, a mutant mouse strain with skeletal abnormalities and hypophosphatemia: identification as an allele of 'Hyp'.

BACKGROUND: The endopeptidase encoded by Phex (phosphate-regulating gene with homologies to endopeptidases linked to the X chromosome) is critical for regulation of bone matrix mineralization and phosphate homeostasis. PHEX has been identified from analyses of human X-linked hypophosphatemic rickets and Hyp mutant mouse models. We here demonstrated a newly established dwarfism-like Kbus/Idr mouse line to be a novel Hyp model. METHODS: Histopathological and X-ray examination with cross experiments were performed to characterize Kbus/Idr. RT-PCR-based and exon-directed PCR screening performed to identify the presence of genetic alteration. Biochemical assays were also performed to evaluate activity of alkaline phosphatase. RESULTS: Kbus/Idr, characterized by bone mineralization defects, was found to be inherited in an X chromosome-linked dominant manner. RT-PCR experiments showed that a novel mutation spanning exon 16 and 18 causing hypophosphatemic rickets. Alkaline phosphatase activity, as an osteoblast marker, demonstrated raised levels in the bone marrow of Kbus/Idr independent of the age. CONCLUSIONS: Kbus mice should serve as a useful research tool exploring molecular mechanisms underlying aberrant Phex-associated pathophysiological phenomena.

A comparison of the effects of different water exercise programs on balance ability in elderly people.

This study compared the effects of 2 types of water exercise programs on balance ability in the elderly. Thirty healthy elderly persons (60.7 +/- 4.1 yr) were randomly assigned to a deep-water-running exercise (DWRE, n = 15) group or a normal water exercise (NWE, n = 15) group. The participants completed a twice-weekly water exercise intervention for 12 wk. Exercise sessions comprised a 10-min warm-up on land, 20 min of water-walking exercise, 30 min of water exercise while separated into NWE and DWRE, a 10-min rest on land, and 10 min of recreation and relaxation in water. Postural-sway distance and tandem-walking time were decreased significantly in DWRE. Postural-sway area was decreased significantly in NWE. In both groups, simple reaction times were significantly decreased. The findings of this study show that a water exercise program including deep-water running is much better than normal water exercise for improving dynamic balance ability in the elderly.

Redox-dependent structural ambivalence of the cytoplasmic domain in the inner ear-specific cadherin 23 isoform.

Cadherin 23 (Cdh23), an essential factor in inner ear mechano-electric transduction, exists in two alternatively spliced forms, Cdh23(+68) and Cdh23(-68), depending on the presence and absence of exon 68. Cdh23(+68) is inner ear-specific. The exon 68-corresponding region confers an alpha-helical configuration upon the cytoplasmic domain (Cy) and includes a cysteine residue, Cys(3240). We demonstrate here that Cy(+68) as well as the transmembrane (TM) plus Cy(+68) region is present in two different forms in transfected cells, reduced and non-reduced, the latter existing in more compact configuration than the former. The observed characteristic of Cy(+68) was completely abolished by Cys(3240)Ala substitution. Treatment of TMCy(+68)-transfected cells with diethyl maleate, a glutathione depleting reagent, resulted in conversion of the non-reduced to the reduced form of TMCy(+68), suggesting glutathione to be a Cys(3240)-binding partner. Multiple alignment of mammalian Cdh23Cy sequences indicated the occurrence of conformation-inducible Cys in Cdh23Cy of mammals, but not lower vertebrates. The implications of Cys-dependent structural ambivalence of Cdh23 in inner ear mechanosensation are discussed.

Thermal insulation and body temperature wearing a thermal swimsuit during water immersion.

This study evaluated the effects of a thermal swimsuit on body temperatures, thermoregulatory responses and thermal insulation during 60 min water immersion at rest. Ten healthy male subjects wearing either thermal swimsuits or normal swimsuits were immersed in water (26 degrees C or 29 degrees C). Esophageal temperature, skin temperatures and oxygen consumption were measured during the experiments. Metabolic heat production was calculated from oxygen consumption. Heat loss from skin to the water was calculated from the metabolic heat production and the change in mean body temperature during water immersion. Total insulation and tissue insulation were estimated by dividing the temperature difference between the esophagus and the water or the esophagus and the skin with heat loss from the skin. Esophageal temperature with a thermal swimsuit was higher than that with a normal swimsuit at the end of immersion in both water temperature conditions (p<0.05). Oxygen consumption, metabolic heat production and heat loss from the skin were less with the thermal swimsuit than with a normal swimsuit in both water temperatures (p<0.05). Total insulation with the thermal swimsuit was higher than that with a normal swimsuit due to insulation of the suit at both water temperatures (p<0.05). Tissue insulation was similar in all four conditions, but significantly higher with the thermal swimsuit in both water temperature conditions (p<0.05), perhaps due to of the attenuation of shivering during immersion with a thermal swimsuit. A thermal swimsuit can increase total insulation and reduce heat loss from the skin. Therefore, subjects with thermal swimsuits can maintain higher body temperatures than with a normal swimsuit and reduce shivering thermo-genesis.

Fates of Cdh23/CDH23 with mutations affecting the cytoplasmic region.

BUS/Idr mice carrying a mutant waltzer allele (vbus) are characterized by splayed hair bundles in inner ear sensory cells, providing a mouse homolog of USH1D/DFNB12. RT-PCR-based screening for the presence of mutations in mouse Cdh23, the gene responsible for the waltzer phenotype, has identified a G>A mutation in the donor splice site of intron 67 (Cdh23:c.9633+1G>A: GenBank AF308939.1), indicating that two altered Cdh23 molecules having intron-derived COOH-terminal structures could be generated in BUS mouse tissues. Immunochemical analyses with anti-Cdh23 antibodies showed, however, no clear Cdh23-related proteins in vbus/vbus tissues, while the antibodies immunoreacted with approximately 350 kDa proteins in control mice. Immunofluorescent experiments revealed considerable weakening of Cdh23 signals in sensory hair cell stereocilia and Reissner's membrane in the vbus/vbus inner ear, and transmission electron microscopy demonstrated abundant autophagosome/autolysosome vesicles, suggesting aberrant Cdh23:c.9633+1G>A-derived protein-induced acceleration of lysosomal bulk degradation of proteins. In transfection experiments, signal sequence-preceded FLAG-tagged transmembrane plus cytoplasmic regions (TMCy) of tissue-specific Cdh23(+/-68) isoforms were localized to filamentous actin-rich protrusions and the plasma membrane of cultured cells, whereas FLAG-TMCy:c.9633+1G>A proteins were highly insoluble and retained in the cytoplasm. In contrast, FLAG-tagged TMCy:p.Arg3175His and human TMCy:c.9625_9626insC forms were both localized to the plasma membrane in cultured cells, allowing prediction that USH1D-associated CDH23:p.Arg3175His and CDH23:c.9625_9626insC proteins could be transported to the plasma membrane in vivo. The present results thus suggest different fates of CDH23/Cdh23 with mutations affecting the cytoplasmic region.

Possible involvement of myosin-X in intercellular adhesion: importance of serial pleckstrin homology regions for intracellular localization.

Subcellular fractionation experiments with mouse hepatocytes, combined with sodium dodecylsulfate (SDS)-polyacrylamide gel electrophoresis (PAGE)-immunoblot analysis using antibodies against two different tail regions of mouse myosin-X demonstrated a 240 kDa molecular mass to be associated with the plasma membrane-rich P2 fraction. The basolateral plasma membrane fraction, but not the brush border fraction, isolated from renal cortices also contained the 240 kDa form of myosin-X. In an attempt to assess relative contributions of possible functional domains in the tail of myosin-X to localization and function, cDNA corresponding to all three pleckstrin homology (PH) domains and different regions (PH1, 2 and 3, and the two subdomains of PH1: PHS1 and PHS2), as well as the myosin tail homology 4 domain (MyTH4) and the band4.1/ezrin/radixin/moesin-like domain (FERM) were separately inserted into the pEGFP vector and expressed in cultured COS-1 cells. As a result, two distinct regions responsible for localization were identified with regard to PH: one covers all three forms that tends to localize to regions of dynamic actin, such as membrane ruffles, lamellipodia and thick cortical actin bundles at the sites of cell-cell adhesion in a Rac- and Cdc42-dependent manner. The other covers PHS1 and PH2 that localizes to filopodia, filopodial puncta and the sites of intercellular adhesion in a Cdc42-dependent manner. Expression of green fluorescent protein (GFP)-MyTH4 fusion protein resulted in formation of phalloidin-positive granules, while GFP-FERM affected the actin cytoskeletal system in a distinctly different way. Taken altogether, the results lend support to the view that myosin-X is involved in cell-cell adhesion-associated signaling-linked membrane and/or cytoskeleton reorganization.