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  • 1
    ISSN: 1432-1777
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1777
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The T-box motif is present in a family of gene whose structural features and expression patterns support their involvement in developmental gene regulation. Previously, sequence comparisons among the T-box domains of ten vertebrate and invertebrate T-box (Tbx) genes established a phylogenetic tree with three major branches. The Tbx2-related branch includes mouse Mm-Tbx2 and Mm-Tbx3, Drosophila optomotor-blind (Dm-Omb), and Caenorhabditis elegans Ce-Tbx2 and Ce-Tbx7 genes. From the localization of Mm-Tbx2 to Chromosome (Chr) 11, we focused our search for the human homolog, Hs-TBX2, within a region of synteny conservation on Chr 17q. We used Dm-Omb polymerase chain reaction (PCR) primers to amplify a 137-basepair (bp) product from human genomic, Chr 17 monochromosome hybrid, and fetal kidney cDNA templates. The human PCR product showed 89% DNA sequence identity and 100% petide sequence identity to the corresponding T-box segment of Mm-Tbx2. The putative Hs-TBX2 locus was isolated within a YAC contig that included three anonymous markers, D17S792, D17S794, and D17S948, located at Chr 17q21-22. Hybridization-and PCR-based screening of a 15-week fetal kidney cDNA library yielded several TBX2 clones. Sequence analysis of clone λcTBX2-1 confirmed homology to Mm-Tbx2-90% DNA sequence identity over 283 nt, and 96% peptide sequence identity over 94 amino acids. Similar analysis of Hs-TBX2 cosmid 15F11 confirmed the cDNA coding sequence and also identified a 1.7-kb intron located at the same relative position as in Mm-Tbx2. Phylogenetic analyses of the T-box domain sequences found in several vertebrate and invertebrate species further suggested that the putative human TBX2 and mouse Tbx2 are true homologs. Northern blot analysis identified two major TBX2 transcripts of 3.5 and 2.8kb, with high levels of TBX2 expression in fetal kidney and lung; and in adult kidney, lung, ovary, prostate, spleen, and testis. Reduced expression levels were seen in heart, white blood cells, small intestine, and thymus. These results suggest that Hs-TBX2 could play important roles in both developmental and postnatal gene regulation.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-041X
    Keywords: Key words T-box genes ; Zebrafish ; Fins ; Evolution ; Gene duplication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The presence of two sets of paired appendages is one of the defining features of jawed vertebrates. We are interested in identifying genetic systems that could have been responsible for the origin of the first set of such appendages, for their subsequent duplication at a different axial level, and/or for the generation of their distinct identities. It has been hypothesized that four genes of the T-box gene family (Tbx2–Tbx5) played important roles in the course of vertebrate limb evolution. To test this idea, we characterized the orthologs of tetrapod limb-expressed T-box genes from a teleost, Danio rerio. Here we report isolation of three of these genes, tbx2, tbx4, and tbx5. We found that their expression patterns are remarkably similar to those of their tetrapod counterparts. In particular, expression of tbx5 and tbx4 is restricted to pectoral and pelvic fin buds, respectively, while tbx2 can be detected at the anterior and posterior margins of the outgrowing fin buds. This, in combination with conserved expression patterns in other tissues, suggests that the last common ancestor of teleosts and tetrapods possessed all four of these limb-expressed T-box genes (Tbx2–Tbx5), and that these genes had already acquired, and have subsequently maintained, their gene-specific functions. Furthermore, this evidence provides molecular support for the notion that teleost pectoral and pelvic fins and tetrapod fore- and hindlimbs, respectively, are homologous structures, as suggested by comparative morphological analyses.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Genetics 19 (1985), S. 179-208 
    ISSN: 0066-4197
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
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