Schematic presentation of the cell array-based protein localization procedure. (A) Open reading frames (ORFs) derived from human chromosome 21 were cloned into a mammalian expression vector containing an amino-terminal His6 tag, spotted in an array format and reverse transfected into an HEK293T cell line. (B) Proteins expressed on the cell arrays were detected using anti-His antibody and a set of organelle counterstaining was performed. (C) The efficiency of protein expression and labeling was monitored using a BioCCD laser scanning system. The green signal indicates the expression of enhanced green fluorescent protein (EGFP). The red signal indicates His6-tagged protein. (D) For single-cell analysis, fluorescent and confocal microscopy was used. The red signal in the 1000× magnification images represents expressed C21orf25 protein, whereas the green and blue signals represent labeled microtubule and nucleus, respectively.