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Dive into the research topics where Christian R. Marshall is active.

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Featured researches published by Christian R. Marshall.


BMC Evolutionary Biology | 2008

Gene structure evolution of the Na+-Ca2+ exchanger (NCX) family.

Caly On; Christian R. Marshall; Nansheng Chen; Christopher D. Moyes; Glen F. Tibbits

BackgroundThe Na+-Ca2+ exchanger (NCX) is an important regulator of cytosolic Ca2+ levels. Many of its structural features are highly conserved across a wide range of species. Invertebrates have a single NCX gene, whereas vertebrate species have multiple NCX genes as a result of at least two duplication events. To examine the molecular evolution of NCX genes and understand the role of duplicated genes in the evolution of the vertebrate NCX gene family, we carried out phylogenetic analyses of NCX genes and compared NCX gene structures from sequenced genomes and individual clones.ResultsA single NCX in invertebrates and the protochordate Ciona, and the presence of at least four NCX genes in the genomes of teleosts, an amphibian, and a reptile suggest that a four member gene family arose in a basal vertebrate. Extensive examination of mammalian and avian genomes and synteny analysis argue that NCX4 may be lost in these lineages. Duplicates for NCX1, NCX2, and NCX4 were found in all sequenced teleost genomes. The presence of seven genes encoding NCX homologs may provide teleosts with the functional specialization analogous to the alternate splicing strategy seen with the three NCX mammalian homologs.ConclusionWe have demonstrated that NCX4 is present in teleost, amphibian and reptilian species but has been secondarily and independently lost in mammals and birds. Comparative studies on conserved vertebrate homologs have provided a possible evolutionary route taken by gene duplicates subfunctionalization by minimizing homolog number.


American Journal of Physiology-cell Physiology | 2009

Characterization of zebrafish (Danio rerio) NCX4: a novel NCX with distinct electrophysiological properties

Caly On; Christian R. Marshall; Steve F. Perry; Hoa Dinh Le; Vladimir Yurkov; Alexander Omelchenko; Mark Hnatowich; Glen F. Tibbits

Members of the Na+/Ca2+ exchanger (NCX) family are important regulators of cytosolic Ca2+ in myriad tissues and are highly conserved across a wide range of species. Three distinct NCX genes and numerous splice variants exist in mammals, many of which have been characterized in a variety of heterologous expression systems. Recently, however, we discovered a fourth NCX gene (NCX4), which is found exclusively in teleost, amphibian, and reptilian genomes. Zebrafish (Danio rerio) NCX4a encodes for a protein of 939 amino acids and shows a high degree of identity with known NCXs. Although knockdown of NCX4a activity in zebrafish embryos has been shown to alter left-right patterning, it has not been demonstrated that NCX4a functions as a NCX. In this study, we 1) demonstrated, for the first time, that this gene encodes for a novel NCX; 2) characterized the tissue distribution of zebrafish NCX4a; and 3) evaluated its kinetic and transport properties. While ubiquitously expressed, the highest levels of NCX4a expression occurred in the brain and eyes. NCX4a exhibits modest levels of Na+-dependent inactivation and requires much higher levels of regulatory Ca2+ to activate outward exchange currents. NCX4a also exhibited extremely fast recovery from Na+-dependent inactivation of outward currents, faster than any previously characterized wild-type exchanger. While this result suggests that the Na+-dependent inactive state of NCX4a is far less stable than in other NCX family members, this exchanger was still strongly inhibited by 2 microM exchanger inhibitory peptide. We demonstrated that a new putative member of the NCX gene family, NCX4a, encodes for a NCX with unique functional properties. These data will be useful in understanding the role that NCX4a plays in embryological development as well as in the adult, where it is expressed ubiquitously.


American Journal of Physiology-regulatory Integrative and Comparative Physiology | 2000

Ca2+ binding to cardiac troponin C: effects of temperature and pH on mammalian and salmonid isoforms

Todd E. Gillis; Christian R. Marshall; Xiao-Hua Xue; Thor J. Borgford; Glen F. Tibbits


Physiological Genomics | 2007

Evolution and structural diversification of hyperpolarization-activated cyclic nucleotide-gated channel genes

Heather A. Jackson; Christian R. Marshall; Eric A. Accili


Physiological Genomics | 2007

Functional and evolutionary relationships of troponin C

Todd E. Gillis; Christian R. Marshall; Glen F. Tibbits


American Journal of Physiology-cell Physiology | 2001

Temperature dependence of cloned mammalian and salmonid cardiac Na+/Ca2+ exchanger isoforms

Chadwick L. Elias; Xiao-Hua Xue; Christian R. Marshall; Alexander Omelchenko; Glen F. Tibbits


Physiological Genomics | 2005

Phylogeny of Na+/Ca2+ exchanger (NCX) genes from genomic data identifies new gene duplications and a new family member in fish species

Christian R. Marshall; Joanne A. Fox; Stefanie L. Butland; B. F. Francis Ouellette; Fiona S. L. Brinkman; Glen F. Tibbits


American Journal of Physiology-cell Physiology | 2002

Determinants of cardiac Na+/Ca2+exchanger temperature dependence: NH2-terminal transmembrane segments

Christian R. Marshall; Chadwick L. Elias; Xiao-Hua Xue; Hoa Dinh Le; Alexander Omelchenko; Glen F. Tibbits


Annals of the New York Academy of Sciences | 2006

Temperature Dependence of Cardiac Na+/Ca2+ Exchanger

Christian R. Marshall; Xiao-Hua Xue; Hoa Dinh Le; Alexander Omelchenko; Glen F. Tibbits


American Journal of Physiology-cell Physiology | 2002

Determinants of cardiac Na/Ca 2 exchanger temperature dependence: NH 2 -terminal transmembrane segments

Christian R. Marshall; Chadwick L. Elias; Xiao-Hua Xue; Hoa Dinh Le; Alexander Omelchenko; Glen F. Tibbits

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Xiao-Hua Xue

Simon Fraser University

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Alexander Omelchenko

St. Boniface General Hospital

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Hoa Dinh Le

University of Manitoba

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Chadwick L. Elias

St. Boniface General Hospital

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Caly On

Family Research Institute

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B. F. Francis Ouellette

Ontario Institute for Cancer Research

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Eric A. Accili

University of British Columbia

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Heather A. Jackson

University of British Columbia

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