Abstract

In vertebrates, the majority of homeobox (HBox) genes are found in four clusters and this structural organization is believed to be of functional importance. Many HBox genes sustain their expression in the appendages of the adult newt. To further understand their regulation, the genomic loci of four newt HBox genes (two from the human HBox (HOX)-2 complex and two from the HOX-3 complex) were analysed and compared with homologous loci in other vertebrates. Notophthalmus viridescens HBox (NvHBox) genes were selected from a ΛEMBL3 library and analysed by restriction mapping and nucleotide (nt) sequencing. The nt sequences of the NvHBox genes have a very high degree of homology (more than 90%) with the human and mouse HBox genes, HOX-3.3, HOX-3.4, HOX-2.7 and HOX-2.8. The sequences flanking the HBox are also very homologous to their human and mouse counterparts. Moreover, the size of the DNA spacer separating NvHBox-3.3 from NvHBox-3.4, and NvHBox-2.7 from NvHBox-2.8 in the newt is similar in the homologous regions of the mouse and human, despite there being a C value ten times greater in the newt genome. Finally, three of these NvHBox genes are expressed in the limbs of the adult newt.

Author Keywords: Genomic loci; homeodomain; regeneration; Notophthalmus viridescens; evolution; urodele; phage Λ

Abbreviations: aa, amino acid(s); ANT, the antennapedia complex of genes encoding homeobox proteins in Drosophila; bp, base pair(s); BX, the bithorax complex of genes encoding homeobox proteins in Drosophila; cDNA, DNA complementary to RNA; HBox, homeobox(es) or 180 nt encoding the homeodomain; homeodomain, specific domain of 60 aa that confers DNA-binding properties to a protein; HOX, human HBox; Hox, mouse HBox; kb, kilobase(s) or 1000 bp; nt, nucleotide(s); NvHBox, Notophthalmus viridescens HBox; oligo, oligodeoxyribonucleotide

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Corresponding author. Correspondence to: Dr. P. Savard, Unité d'Ontogénèse et de Génétique Mol., Centre de Recherche du CHUL, Université Laval, 2705 Blv. Laurier, , Québec, GIV 4G2, , Canada Tel. (418) 654-2103; Fax (418) 654-2748.