Hcn1 Is a Tremorgenic Genetic Component in a Rat Model of Essential Tremor

Genetic factors are thought to play a major role in the etiology of essential tremor (ET); however, few genetic changes that induce ET have been identified to date. In the present study, to find genes responsible for the development of ET, we employed a rat model system consisting of a tremulous mutant strain, TRM/Kyo (TRM), and its substrain TRMR/Kyo (TRMR). The TRM rat is homozygous for the tremor (tm) mutation and shows spontaneous tremors resembling human ET. The TRMR rat also carries a homozygous tm mutation but shows no tremor, leading us to hypothesize that TRM rats carry one or more genes implicated in the development of ET in addition to the tm mutation. We used a positional cloning approach and found a missense mutation (c. 1061 C>T, p. A354V) in the hyperpolarization-activated cyclic nucleotide-gated 1 channel (Hcn1) gene. The A354V HCN1 failed to conduct hyperpolarization-activated currents in vitro, implicating it as a loss-of-function mutation. Blocking HCN1 channels with ZD7288 in vivo evoked kinetic tremors in nontremulous TRMR rats. We also found neuronal activation of the inferior olive (IO) in both ZD7288-treated TRMR and non-treated TRM rats and a reduced incidence of tremor in the IO-lesioned TRM rats, suggesting a critical role of the IO in tremorgenesis. A rat strain carrying the A354V mutation alone on a genetic background identical to that of the TRM rats showed no tremor. Together, these data indicate that body tremors emerge when the two mutant loci, tm and Hcn1^A354V, are combined in a rat model of ET. In this model, HCN1 channels play an important role in the tremorgenesis of ET. We propose that oligogenic, most probably digenic, inheritance is responsible for the genetic heterogeneity of ET.     

TRIP12 promotes small-molecule-induced degradation through K29/K48-branched ubiquitin chains

1. Download : Download high-res image (184KB)
2. Download : Download full-size image

     

Multiple alleles at <Emphasis Type="Italic">Early flowering 1</Emphasis> locus making variation in the basic vegetative growth period in rice (<Emphasis Type="Italic">Oryza</Emphasis> <Emphasis Type="Italic">sativa</Emphasis> L.)

A recently established rice breeding program in low latitudes aims to develop varieties with extremely long basic vegetative growth (BVG) periods and weak photoperiod sensitivities. The Taiwanese japonica variety Taichung 65 (T65) harbors a recessive allele ef1 at the Ef1 (Early flowering 1) locus, thereby exhibiting an extremely long BVG period. The previous reported functional allele Ehd1 (Early heading date 1), located on chromosome 10, encodes a B-type response regulator, thereby shortening the BVG period, whereas its nonfunctional allele ehd1 greatly prolongs the BVG period. A conventional analysis using F₂ and F₃ populations and a subsequent CAPS analysis based on the amino acid sequences of Ehd1 and ehd1 showed that Ef1 and Ehd1 were at the same locus. The CAPS analysis also indicated that the Taiwanese japonica varieties with extremely long BVG periods all harbor ef1, but that ef1 does not exist among indica and japonica varieties in the low latitudes. Since ef1 has not been found in any japonica varieties outside Taiwan, this allele might have originated in Taiwan. Sequence analysis revealed that the mutant allele ef1-h, which prolongs the BVG period even more than ef1 does, harbors an mPing insertion in exon 2, which causes the complete loss of gene function. Our results indicate that both ef1 or ef1-h alleles can be used as new gene sources in developing rice varieties with extremely long BVG periods for low latitudes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Entrapment of Ciliates at the Water-Air Interface

The importance of water-air interfaces (WAI) on microorganism activities has been recognized by many researchers. In this paper, we report a novel phenomenon: the entrapment of ciliates Tetrahymena at the WAI. We first characterized the behavior of cells at the interface and showed that the cells'' swimming velocity was considerably reduced at the WAI. To verify the possible causes of the entrapment, we investigated the effects of positive chemotaxis for oxygen, negative geotaxis and surface properties. Even though the taxes were still effective, the entrapment phenomenon was not dependent on the physiological conditions, but was instead affected by the physical properties at the interface. This knowledge is useful for a better understanding of the physiology of microorganisms at interfaces in nature and in industry.     

Crystallization and preliminary cryogenic X-ray diffraction analyses of protein L-isoaspartyl O-methyltransferase from human fetal brain

Recombinant human fetal brain protein L-isoaspartyl O-methyltransferase, EC 2.1.1.77, was crystallized in PEG 8000 with adenosine homocysteine by a macroseeding technique. The space group was P2₁ with a = 47.4 Å, b = 53.9 Å, c = 48.7 Å and β = 116.4° for cryofrozen crystals at 90 K. The crystals diffracted to 2.1 Å and have one molecule per asymmetric unit. Proteins 28:457–460, 1997. © 1997 Wiley-Liss, Inc.     

Inhibitory effect of OPC-15161, a component of fungus Thielavia minor,on proliferation and extracellular matrix production of rat cultured hepatic stellate cells

A component of fungus Thielavia minor, OPC-15161, has been shown to inhibit the proliferation and extracellular matrix production of extracellular matrix-producing mesangial cells in the kidney in vivo. In this study, we examined the effects of OPC-15161 on the proliferation and extracellular matrix production of rat cultured hepatic stellate cells (HSCs). To determine the effect of OPC-15161 on proliferation of HSCs, the cell number and the uptake of [³H]thymidine were investigated in the presence and absence of interleukin-1β (IL-1β). IL-1β significantly increased the uptake of [³H]thymidine in the HSCs, and the addition of OPC-15161 inhibited the uptake in a dose-dependent manner. The cell number of HSCs was also increased by IL-1β, which was inhibited by OPC-15161. Production of extracellular matrix by OPC-15161 was studied by the production of [³H]-hydroxyproline in the presence and absence of transforming growth factor-β1 (TGF-β1). TGF-β1 significantly increased the production of [³H]-hydroxyproline in the cells, whereas the addition of OPC-15161 inhibited this effect dose dependently. We also investigated the effects of OPC-15161 on Ca²⁺ mobilization and measured D-myo-inositol 1,4,5-triphosphate (IP₃) in the HSCs. IL-1β induced the increase of intracellular Ca²⁺ and IP₃ concentrations in the HSCs, which were decreased by OPC-15161. Based on these results, we conclude that OPC-15161 inhibited the proliferation and production of hydroxyproline in cultured rat HSCs, and thus, it may have a role in prevention of liver fibrosis in vivo. J. Cell. Physiol. 174:398–406, 1998. © 1998 Wiley-Liss, Inc.     

The life cycle of Gyrodinium instriatum (Dinophyceae) in culture*

The life cycle events of an unarmored dinoflagellate Gyrodinium instriatum Freudenthal et Lee has been investigated using clonal cultures. After the inoculation of vegetative cells into fresh medium, clumping of gametes was observed after a period of 10 days. In the clumps, a number of gametes were observed to be swimming in close contact with each other, pairing successively and then forming a plano-zygote. This clumping behavior is considered to be useful in the performance of sexual reproduction, particularly in the event of low cell density, because it increases the chance of fusion. Gametes of this species were most often isogarnous, although apparent amsogamous fusions were occasionally observed. When planozygotes were isolated and placed in fresh medium, they enlarged their size and finally divided into two cells. The daughter cells continued to multiply by binary fission and produced vegetative cells. Thus, G. instriatum has an alternative cycle between vegetative cells and zygotes without a hypnozygote stage. However, cysts of this species were transformed from large motile cells (pre-cyst cells) which are oblong and dorso-ventrally flattened in shape. These mottle pre-cyst cells have two longitudinal flagella, which may indicate that cysts of this species are of zygote origin. On the basis of these results, the relationship between zygotes and pre-cysts of G. instriatum is discussed. Excystment was enhanced by dark and cold treatments prior to the incubation for germination experiments with a germination success rate of 26–64%. Encystment was greatly inhibited by the lack of dark and cold treatments.