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 the apical ectodermal ridge (AER) during limb development as well as in the distal region of the ectoderm. The 9aaTAD motif is a transactivation domain present in a large number of yeast and animal transcription factors. In SP9, the motif is inactive. Belongs to the Sp1 C2H2-type zinc-finger protein family.