Molecular Characterisation of Three Murine HOX11‐Related Homeobox Genes, Tlx‐1, −2, and −3, and Restricted Expression of Tlx‐1 during Embryogenesis: murine/homeobox/cloning/motif/expression

Elevated expression of the human homeobox gene HOX11 has been implicated in T cell acute lymphoblastic leukemia. We report here the isolation and characterisation of three murine genes, Tlx‐1, −2, and −3, which are related to HOX11 and constitute a new class of homeobox genes. Sequence analysis indicates that Tlx‐1 is a murine homolog of HOX11. The expression during development of Tlx‐1 was studied by in situ hybridization. Tlx‐1 expression was found in the first branchial arch, the pancreas, the hindbrain and the epidermis of the ear of the developing embryos. Localized expression of Tlx‐1 in these developing structures suggests that it might play a specific role during post‐implantation development and its aberrant expression might be involved in oncogenesis. The homeodomains of Tlx‐2 and −3 are found to be 75% and 80% identical to that of Tlx‐1, respectively. In addition to the homeodomain, the three Tlx proteins also share four conserved motifs (TH1–TH4). Interestingly, these motifs are also found in other developmental control genes and transcription factors, suggesting a functional role in transcriptional regulation.