Phylogenetic analysis of B-raf exon 8b.
(A) Schematic representation of B-raf genomic structure between exon 8 and exon 9 in different species. Positioning of intronic and exonic sequences was obtained using ClustalW2 multiple sequence alignment program as described in Suplementary Figure. The size of introns is indicated. Exon 8b sequences are found only in eutherians, but not in other mammals and in chicken. (B) Exon 8b amino-acid sequence conservation in eutherians. Evidence for the presence of B-raf exon 8b sequences on genomic DNA (G) or transcripts (T) is indicated on the right. B-raf transcripts containing exon 8b have been reported in mouse (This study and Barnier et al., 1995 ; cDNA accession number AJ276308) and rat (EST accession number BF543389). (C) Exon 8b is not expressed in human brain. B-Raf isoforms expression was analyzed in human and mouse total brain by RT-PCR as described in Materials and Methods.