Fox3 is one of a family of mammalian homologues of Fox-1. The Fox proteins are about 46kDa in size, and each includes a central highly conserved RRM type RNA recognition motif. Much interest has focused on Fox3 as a result of the recent finding that this protein corresponds to NeuN, a neuronal nuclear antigen. NeuN/Fox-3 has a function in RNA splicing and is expressed heavily and specifically in neuronal nuclei and cytoplasm. Our antibody was raised against the N-terminal 100 amino acids of human Fox3 as expressed in and purified from E. coli. We did not use full length Fox3 as immunogen since the three mammalian Fox homologues, namely Fox1, Fox2 and Fox3, include virtually identical RRM motifs. The N-terminal region of the three molecules are much more variable in the three molecules so antibodies specific for each of the three molecules can therefore be generated.