Isolation and Characterization of a Gene from the DiGeorge Chromosomal Region Homologous to the MouseTbx1Gene

Abstract

DiGeorge syndrome, velocardiofacial syndrome, conotruncal anomaly face syndrome, and isolated and familial forms of conotruncal cardiac defects have been associated with deletions of chromosomal region 22q11.2. This report describes the identification, cloning, and characterization of the humanTBX1gene, which maps to the center of the DiGeorge chromosomal region. Further, we have extended the mouse cDNA sequence to permit comparisons between human and mouseTbx1. TBX1is a member of a phylogenetically conserved family of genes that share a common DNA-binding domain, the T-box. T-box genes are transcription factors involved in the regulation of developmental processes. There is 98% amino acid identity between human and mouse TBX1 proteins overall, and within the T-box domain, the proteins are identical except for two amino acids. Expression of humanTBX1in adult and fetal tissues, as determined by Northern blot analysis, is similar to that found in the mouse. Additionally, using 3′RACE, we obtained a differentially spliced message in adult skeletal muscle. MouseTbx1has been previously shown to be expressed during early embryogenesis in the pharyngeal arches, pouches, and otic vesicle. Later in development, expression is seen in the vertebral column and tooth bud. Thus, humanTBX1is a candidate for some of the features seen in the 22q11 deletion syndrome.