Abstract
The expression of midbrain homeobox-1 (mbx1) defines a discrete region in the vertebrate neural plate that will give rise to the mesencephalon, as well as subregions of the diencephalon and retinal field. Here, we report on the identification and cloning of a second Mbx gene in zebrafish, termed mbx2. Genomic sequence comparison suggests that mbx1 and mbx2 are derived from the duplication of a single putative ancestral gene that is conserved in other vertebrates as a single copy gene. Furthermore, phylogenetic analyses indicate that the mbx genes belong to a novel subgroup of paired-like homeobox genes. Finally, quantitative reverse transcriptase-PCR and whole mount in situ hybridization experiments revealed a pattern of partial spatiotemporal expression divergence between the mbx paralogs that correlates with sequence divergence in noncoding regulatory domains. Our data support a subfunctionalization model that may explain the retention of duplicate mbx genes in teleosts.
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Acknowledgements
The authors thank Hazel Sive for support and guidance during the early stages of this project, Claire Kuo and Henry Hong for excellent technical assistance, and Ashley Bruce and members of the Tropepe and Bruce labs for helpful comments on this manuscript. This research was supported by grants from Canada Foundation for Innovation, Ontario Innovations Trust, and the Natural Sciences and Engineering Research Council of Canada.
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Communicated by M. Hammerschmidt
L. Chang and B. Khoo contributed equally to this work.
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Chang, L., Khoo, B., Wong, L. et al. Genomic sequence and spatiotemporal expression comparison of zebrafish mbx1 and its paralog, mbx2 . Dev Genes Evol 216, 647–654 (2006). https://doi.org/10.1007/s00427-006-0082-7
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DOI: https://doi.org/10.1007/s00427-006-0082-7