FANCD2 immunoblot patterns in FA patients, including FA revertant. (A) FA core samples failed to monoubiquitinate FANCD2 and show only the lower unmodified short (FANCD2-S) isoform, whereas non-FA samples show both the FANCD2-S and the long monoubiquitinated (FANCD2-L) isoforms. FA patients are referred to by unique EGFA identification numbers. (B) Detection of FA reversion by the FANCD2 pattern analysis. Revertant patient EGFA008 samples show typical FA in primary fibroblasts pattern (a single FANCD2-L isoform, indicated as 1), whereas fresh PHA-stimulated lymphocytes (arrow 2) and the EBV-immortalized B-cell line (arrow 3) show both the FANCD2-S and FANCD2-L isoforms. Normal and nonrevertant EGFA005 are shown as controls. Short (top panel) and medium (bottom panel) exposures are shown.