Meeting Abstract
P1.13 Monday, Jan. 4 Conserved Regulatory Elements found in the Lamprey Hedgehog Loci KANO, S*; XIAO, J; OSORIO, J; HADZHIEV, Y; EKKER, M; RETAUX, S; CNRS, Gif-sur-Yvette, France; CNRS, Gif-sur-Yvette, France; CNRS, Gif-sur-Yvette, France; University of Birmingham, UK; University of Ottawa, Canada; CNRS, Gif-sur-Yvette, France kano@inaf.cnrs-gif.fr
The lamprey is the key animal to study the evolution of morphological traits, especially at the emergence of craniates. Among genes associated with craniate morphogenesis, sonic hedgehog (shh) is essential, being expressed at the forebrain and other midline tissues such as notochord and floor plate. Previous studies reported that lamprey hedgehog is expressed similarly to gnathostome Shh, which suggests that the regulatory logic for gene expression is evolutionarily conserved between lampreys and other vertebrates. To clarify this hypothesis, genomic sequences of lamprey hedgehog loci were determined in two lamprey species, the river lamprey Lampetra fluviatilis (Lf) and the sea lamprey Petromyzon marinus. We concluded that the lamprey genomes fundamentally contain only 2 hedgehog genes, named Hha and Hhb. Phylogenetic analyses indicated that they are lamprey lineage specific paralogs, which belong to the Shh/Ihh clade. In L. fluviatilis embryos, both genes are expressed almost identically to each other and similar to Shh, while expression at the the zona limitans intrathalamica (ZLI) is absent in LfHha. Phylogenetic footprinting with other telost Shh loci was feasible to reveal putative lamprey conserved regulatory elements (CREs) presenting similarity with the ar-C motif previously reported in zebrafish. The putative CREs were quite dispersed, spreading over 180-800bp against approx. 140-180bp in other vertebrates. We have validated that the lamprey putative CREs function in zebrafish embryos, and some candidates are still under functional test. These findings suggest an evolutionary scenario associated with the Shh-type hedgehog and its regulatory logic.
