Transcription factor which plays a key role in limb development. Positively regulates FGF8 expression in the apical ectodermal ridge (AER) and contributes to limb outgrowth in embryos. Detected in early stages of embryos as an oval and 2 stripes at HH stage 5, which becomes two lateral stripes at HH stage 7, running along the anteroposterior body axis from the head ectoderm to the anterior region of the primitive streak. At HH stage 8, strong expression in the anterior neuroectoderm, which forms the central nervous system, is observed, and at HH stage 9, expressed in the most anterior region of the forebrain, midbrain, neural groove and Hensen's node. At HH stage 15-16, the expression is seen in the surface ectoderm of the limb-forming fields, in addition to the neural tube. The expression in the limb field became confined to the distal region of the limb at HH stage 16 and 17, with still scattered signal visible in the surface ectoderm of the limb bud. Strongly expressed in the apical ectodermal ridge (AER) and weakly in the ectoderm in the developing limb bud at HH stage 21. The expression in the AER is detected throughout later stages of limb development. The 9aaTAD motif is a transactivation domain present in a large number of yeast and animal transcription factors. Belongs to the Sp1 C2H2-type zinc-finger protein family.