Forkhead-box (FOX) transcription factors are implicated in carcinogenesis through gene amplification, retroviral integration, or chromosomal translocation. FOXN1, FOXN2 (HTLF), FOXN3 (CHES1), FOXN4 and FOXN5 (FOXR1) constitute the FOXN family. Here, we identified and characterized human FOXN6 (FOXR2) and rodent Foxn6 (Foxr2) orthologs by using bioinformatics. Human FOXN6 gene was identified within human genome sequence RP11-167P23 (AL159987.19), mouse Foxn6 gene within mouse genome sequence RP23-180D16 (AL672293.14), and rat Foxn6 gene within rat genome sequence CH230-264B14 (AC106980.5). FOXN6, RRAGB (RAGB), and KLF8 genes were clustered at human chromosome Xp11.21. Foxn6, Rragb, and Klf8 genes were also clustered at mouse chromosome XF3 as well as at rat chromosome Xq14. Human FOXN6 mRNA was expressed in breast cancer cell line and primary breast cancer. Mouse Foxn6 mRNA was expressed in E9.5 embryo. Human FOXN6 (286 aa) showed 57.7% total-amino-acid identity with human FOXN5, 53.8% total-amino-acid identity with mouse Foxn6 (277 aa), and 52.4% total-amino-acid identity with rat Foxn6 (277 aa). Codon 167-248 of human FOXN6 was the Forkhead domain. FN56 domain (codon 1-69 of FOXN6) was identified as a novel domain conserved among FOXN6 and FOXN5 orthologs. Mammalian FOXN6 orthologs were found consisting of FN56 and FOX domains. Phylogenetic analyses revealed that FOXN family proteins are classified into three subfamilies: i) FOXN6 and FOXN5 orthologs; ii) FOXN1 and FOXN4 orthologs; iii) FOXN2 and FOXN3 orthologs. This is the first report on human FOXN6, mouse Foxn6, and rat Foxn6 genes.

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