Tbx3 gene is a member of a phylogenetically conserved family of genes that share a common DNA binding domain, the T box. T box genes encode transcription factors involved in the regulation of developmental processes. Tbx3 is a transcriptional repressor and is thought to play a role in the anterior/posterior axis of the tetrapod forelimb. Mutations in this gene cause ulnar mammary syndrome, affecting limb, apocrine gland, tooth, hair, and genital development. Alternative splicing of this gene results in three transcript variants encoding different isoforms; however, the full length nature of one variant has not been determined.