Abstract
Somatolactin (SL) plays an essential role in body-color regulation in medaka and is encoded by the color interfere (ci) locus. The ci mutant fish possess constitutively increased numbers of leucophores and a concomitant decrease in visible xanthophores. However, the mechanism of action of SL on these cell types, and the role of SL in body-color regulation in other species, is unknown. In this study, we verified an SL–xanthophore relationship in ci mutant fish using the leucophore free (lf) gene. Histological observation of lf larvae indicated that these mutants do not possess differentiated leucophores. The ci–lf double mutant, whose genotype was confirmed using DNA markers, lacked leucophores; however, the number of xanthophores remained low, demonstrating that leucophores are not necessary for mediating SL signaling to xanthophores. This finding suggests a conserved function for SL in xanthophore regulation across species, rather than the evolution of a medaka-specific and leucophore-dependent role of SL in body-color regulation. Our results also demonstrate that the lf gene has an indispensable role in leucophore development epistatic to SL signaling. The lf gene has not been cloned. The high-resolution recombination map surrounding the lf locus constructed in this study, together with medaka whole genome sequences that will be released soon, will allow the rapid cloning of the lf gene by forward genetic approaches.
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Acknowledgements
The authors thank K. Naruse and E. Nagao of the University of Tokyo for providing marker information around the lf locus. We also thank K. Yori and T. Yamashita for advice on histological sectioning and fish care, respectively. S.F. is a Research Fellow of the Japan Society for the Promotion of Science (JSPS; #17-10821).
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Communicated by M Hammerschmidt
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Fukamachi, S., Wakamatsu, Y. & Mitani, H. Medaka double mutants for color interfere and leucophore free: characterization of the xanthophore–somatolactin relationship using the leucophore free gene. Dev Genes Evol 216, 152–157 (2006). https://doi.org/10.1007/s00427-005-0040-9
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DOI: https://doi.org/10.1007/s00427-005-0040-9