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An ascidian T‐box gene As‐T2 is related to the Tbx6 subfamily and is associated with embryonic muscle cell differentiation
Author(s) -
Mitani Yasuo,
Takahashi Hiroki,
Satoh Nori
Publication year - 1999
Publication title -
developmental dynamics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.634
H-Index - 141
eISSN - 1097-0177
pISSN - 1058-8388
DOI - 10.1002/(sici)1097-0177(199905)215:1<62::aid-dvdy7>3.0.co;2-x
Subject(s) - brachyury , biology , mesoderm , notochord , subfamily , ectopic expression , paraxial mesoderm , chordate , fundulus , lateral plate mesoderm , microbiology and biotechnology , genetics , gene , myosin , somite , gene family , gene expression , embryonic stem cell , vertebrate , embryogenesis , fishery , fish <actinopterygii>
The T‐box genes, including Brachyury , encode a novel family of transcription factors that play critical roles in various processes of development, in particular, mesoderm formation in chordate embryos. In the case of the ascidian Halocynthia roretzi , the Brachyury ( As‐T ) is expressed exclusively in notochord cells, whereas another T‐box gene ( As‐T2 ) is expressed in the muscle cells and in the tip of the tail of tailbud embryos. In a previous study, we suggested that the combined pattern of the spatial expressions of As‐T and As‐T2 appears to correspond to that of a single vertebrate Brachyury gene (Yasuo et al., Dev Biol 1996;180:773–779). The present molecular phylogenetic analysis suggested that As‐T2 is a divergent member of the T‐box family with a similarity to the Tbx6 subfamily. Vertebrate members of this subfamily are expressed in the posterior paraxial mesoderm, and the mouse Tbx6 is essential for the specification of posterior somite. To investigate the function of As‐T2 , we examined an ectopic‐ and/or overexpression of this gene by injecting synthetic mRNA into fertilized eggs. The results showed that the injection of As‐T2 mRNA induced an ectopic expression of muscle‐specific myosin heavy‐chain gene and actin gene, especially in presumptive epidermal cells. This ectopic muscle‐specific expression was accompanied by the partial suppression of an epidermis‐specific gene expression. The overexpression of As‐T2 , however, rarely affected the expression of As‐T ( Brachyury ) and genes that are expressed in the tailbud. Dev Dyn 1999;215:62–68 . © 1999 Wiley‐Liss, Inc.