Embryonic development depends on the precise spatial and temporal regulation of gene expression by transcription factor proteins. Understanding how transcription factors influence cell fate decisions and subsequent morphogenesis is a fundamental question of developmental biology. We use limb development in the laboratory mouse as a model system to study how transcription factors control the development of specific structures. Many transcription factors that are required to form limb elements have been identified, but we know comparatively little about how these proteins actually function. Most notably, very few of the target genes that are regulated by transcription factors during limb development have been identified. Likewise, we know little about how the expression of the transcription factor genes themselves is controlled.
