Drosophila wingless (wg), shaggy (sgg), armadillo (arm), legless (lgs), pygopus (pygo), pangolin (pan), and engrailed (en) are segment polarity genes implicated in Wg-Arm (WNT-beta-catenin) pathway. Drosophila lgs encodes nuclear scaffold protein functioning as positive regulator for Wg-Arm pathway. Cancer-associated genes BCL9 and BCL9L are human homologs for Drosophila lgs. Here, we identified and characterized rat Bcl9l gene by using bioinformatics. Rat Bcl9l gene, consisting of eight exons, was located within AC124034.4 and AC105645.5 genome sequences. Bcl9l gene was linked to Blr1 gene at rat chromosome 8q22 in the tail-to-tail manner with an interval less than 2 kb. Rat Bcl9l gene was found to encode a 1494-aa Bcl9l protein, which showed 97.7% and 94.2% total-amino-acid identity with mouse Bcl9l and human BCL9L, respectively. B9H1-B9H6 domains, originally identified as conserved regions among mammalian BCL9 and BCL9L homologs, were also identified within rat Bcl9l. B9H1 and B9H2 domains corresponded to HD1 and HD2 domains of Drosophila lgs, functioning as binding regions for Pygo and Arm, respectively. B9H4 domain was characterized by multiple Ser-Pro repeats. Thr 954 within B9H4 domain of rat Bcl9l was conserved in mammalian BCL9 and BCL9L homologs. Phylogenetic analysis revealed that mammalian Bcl9l homologs were more related to human BCL9 than to Drosophila lgs. This is the first report on rat Bcl9l gene.