title: Medaka tert produces multiple variants with differential expression during differentiation in vitro and in vivo.
abstract: Embryonic stem (ES) cells have immortality for self-renewal and pluripotency. Differentiated human cells undergo replicative senescence. In human, the telomerase reverse transcriptase (Tert), namely the catalytic subunit of telomerase, exhibits differential expression to regulate telomerase activity governing cellular immortality or senescence, and telomerase activity or tert expression is a routine marker of pluripotent ES cells. Here we have identified the medaka tert gene and determined its expression and telomerase activity in vivo and in vitro. We found that the medaka tert locus produces five variants called terta to terte encoding isoforms TertA to TertE. The longest TertA consists of 1090 amino acid residues and displays a maximum of 34% identity to the human TERT and all the signature motifs of the Tert family. TertB to TertE are novel isoforms and have considerable truncation due to alternative splicing. The terta RNA is ubiquitous in embryos, adult tissues and cell lines, and accompanies ubiquitous telomerase activity in vivo and in vitro as revealed by TRAP assays. The tertb RNA was restricted to the testis, absent in embryos before gastrulation and barely detectable in various cell lines The tertc transcript was absent in undifferentiated ES cells but became evident upon ES cell differentiation, in vivo it was barely detectable in early embryos and became evident when embryogenesis proceeds. Therefore, ubiquitous terta expression correlates with ubiquitous telomerase activity in medaka, and expression of other tert variants appears to delineate cell differentiation in vitro and in vivo.
authors.affiliation: Department of Biological Sciences, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260.
authors.forename: Feng
authors.initials: F
authors.lastname: Rao
authors.forename: Tiansu
authors.initials: T
authors.lastname: Wang
authors.forename: Mingyou
authors.initials: M
authors.lastname: Li
authors.forename: Zhendong
authors.initials: Z
authors.lastname: Li
authors.forename: Ni
authors.initials: N
authors.lastname: Hong
authors.forename: Haobin
authors.initials: H
authors.lastname: Zhao
authors.forename: Yan
authors.initials: Y
authors.lastname: Yan
authors.forename: Wenqing
authors.initials: W
authors.lastname: Lu
authors.forename: Tiansheng
authors.initials: T
authors.lastname: Chen
authors.forename: Weijia
authors.initials: W
authors.lastname: Wang
authors.forename: Menghuat
authors.initials: M
authors.lastname: Lim
authors.forename: Yongming
authors.initials: Y
authors.lastname: Yuan
authors.forename: Ling
authors.initials: L
authors.lastname: Liu
authors.forename: Lingbing
authors.initials: L
authors.lastname: Zeng
authors.forename: Qiwei
authors.initials: Q
authors.lastname: Wei
authors.forename: Guijun
authors.initials: G
authors.lastname: Guan
authors.forename: Changming
authors.initials: C
authors.lastname: Li
authors.forename: Yunhan
authors.initials: Y
authors.lastname: Hong
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D002460:Cell Line; D002874:Chromosome Mapping; D018076:DNA, Complementary / Q000737:chemistry / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000378:metabolism; D053595:Embryonic Stem Cells / Q000378:metabolism*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D015723:Gene Library; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D009990:Oryzias / Q000196:embryology / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D019098:Telomerase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013737:Testis / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D007527:Isoenzymes; D019098:Telomerase