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  • Articles  (2)
  • Amphioxus embryos  (1)
  • Ascidian embryos  (1)
  • 1995-1999  (2)
  • 1
    Electronic Resource
    Electronic Resource
    cis-Regulatory elements conserved in the proximal promoter region of an ascidian embryonic muscle myosin heavy-chain gene (1996)
    Springer
    Development genes and evolution 206 (1996), S. 54-63 
    Details
    ISSN: 1432-041X
    Keywords: Key words cis-Elements ; Myosin heavy-chain gene ; Muscle-specific expression ; Ascidian embryos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The B-line muscle cells of the ascidian embryo are specified autonomously depending on determinants prelocalized in the myoplasm of unfertilized eggs. Expression of muscle-specific actin and myosin heavy-chain genes commences in the B-line presumptive muscle cells as early as the 32-cell stage. To explore the intrinsic genetic program for this differentiation, we analysed cis-regulatory elements of the Halocynthia roretzi muscle myosin heavy-chain gene (HrMHC1). Comparison of the entire amino acid sequence of HrMHC1 with those of other invertebrates and vertebrates indicated that HrMHC1 resembles myosin heavy-chain of vertebrate skeletal and cardiac muscles. A fusion gene was constructed consisting of 132 bp upstream the 5′-end of HrMHC1 gene fused to a bacterial lacZ reporter. When the fusion gene was microinjected into fertilized eggs, the reporter gene was eventually expressed only in muscle cells of tailbud embryos. It has been reported that 103 bp of sequence 5′ of the transcription start site of the ascidian embryonic muscle actin gene (HrMA4) contains information sufficient for muscle-specific expression (Hikosaka et al. 1994). Comparison of the 132 bp of sequence 5′ of the HrMHC1 gene with the 103 bp of sequence 5′ of the HrMA4 gene revealed several common motifs shared by the two genes (E-box, GATA box and Boxes A, B, T1 and T2). Point mutations inserted into these motifs suggested that the Box T1/T2 (TTTTTTCTTTCA) is critical for the promoter activity of the HrMHC1 gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050030
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  • 2
    Electronic Resource
    Electronic Resource
    Formation of the chordamesoderm in the amphioxus embryo: Analysis with Brachyury and fork head/HNF-3 genes (1997)
    Springer
    Development genes and evolution 207 (1997), S. 1-11 
    Details
    ISSN: 1432-041X
    Keywords: Key words Chordamesoderm formation ; Amphioxus embryos ; Brachyury gene ; fork head/HNF-3 gene ; Evolution of chordates ; Am(Bb)Bra1 and Am(Bb)Bra2 relationships with other Brachyury genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The embryonic development of amphioxus (cephalochordates) has much in common with that of vertebrates, suggesting a close phylogenetic relationship between the two chordate groups. To gain insight into alterations in the genetic cascade that accompanied the evolution of vertebrate embryogenesis, we investigated the formation of the chordamesoderm in amphioxus embryos using the genes Brachyury and fork head/HNF-3 as probes. Am(Bb)Bra1 and Am(Bb)Bra2 are homologues of the mouse Brachyury gene isolated from Branchiostoma belcheri. Molecular phylogenetic analysis suggests that the genes are independently duplicated in the amphioxus lineage. Both genes are initially expressed in the involuting mesoderm of the gastrula, then in the differentiating somites of neurulae, followed by the differentiating notochord and finally in the tail bud of ten-somite stage embryos. On the other hand, Am(Bb)fkh/HNF3-1, an amphioxus (B. belcheri) homologue of the fork head/HNF-3 gene, is initially expressed in the invaginating endoderm and mesoderm, then later in the differentiating notochord and in the tail bud. With respect to these two types of genes, the formation of the notochord and tail bud in amphioxus embryos shows similarity and dissimilarity with that of the notochord and tail bud in vertebrate embryos.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050086
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