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. Expressed in the forebrain, and in the prospective midbrain/hindbrain boundary during early somitogenesis. As development proceeds, also detected in the hindbrain, as well as in the apical fold of the developing pectoral fin, and this expression extends proximally. 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.