Characterization of anti-C9orf72 antibodies. Full-length ORF of the human chromosome 9 open reading frame 72 (C9orf72) gene or the human glial fibrillary acidic protein (GFAP) gene, cloned in the vector that expresses a fusion protein with an N-terminal Xpress tag, was transiently expressed in HEK293 cells. Total protein extract was processed for separation on one-dimensional (1D) or two-dimensional (2D) SDS-PAGE, followed by western blot analysis. (a) 1D, C9orf72 labeled by HPA023873 (left) or sc-138763 (right). (b) 1D, GFAP. (c) 1D, Hsp60, an internal control for protein loading. (d) 2D of the recombinant GFAP protein, HPA023873. (e) 2D identical to (d), GFAP. Lane 1, nontransfected cells; lane 2, cells transfected with the vector expressing GFAP; lane 3, cells transfected with the vector expressing C9orf72. (f) A cross-reactive epitope between C9orf72 and GFAP recognized by HPA023873 aligned by the ClustalW program.