Genomic organization, sequence and chromosomal localization of the mouse Tbr2 gene and a comparative study with Tbr1

Members of the T-box family are known to play critical roles in the embryon ic development of most animal species. Recently, we have isolated its new m ammalian member, Tbr2, from mouse embryonic brain. We have also shown that the expression patterns of Tbr2 and the closely related Tbr1 appear to be r eciprocal in the developing brain; Tbr2 is expressed in mesencephalon and r hombencephalon, but expression of Tbr1 is restricted to telencephalon. To i nvestigate possible structural and functional relationships of Tbr2 and oth er T-box containing genes, we analyzed genomic organization of the murine T br2 gene. The Tbr2 gene is composed of six exons (1353, 155, 122, 159, 62 a nd 1035 bp), and five introns (920, 643, 602, 85 and 2036 bp). This exon/in tron organization is very similar to that of Tbr1. We also analyzed the 3.9 kb sequence of the 5' promoter region flanking the Tbr2 gene and the corre sponding region of the Tbr1 gene. The sites for Brn-2 and Tst-1 were found in the promoter of Tbr2 but not Tbr1. On the contrary, there were eight HNF -3 beta binding sites in the Tbr1 gene promoter but only three in the Tbr2 promoter. The differential presence of putative binding sites for these bra in-specific transcription factors may explain the reciprocal expression of Thr1 and Tbr2. Furthermore, a single chromosomal locus for mouse Tbr2 was a ssigned to 9F3 by fluorescence in-situ hybridization. (C) 2000 Elsevier Sci ence B.V. All rights reserved.