The null allele of the ABCC4 gene is responsible for the PEL-negative phenotype. (A) Integrative Genomics Viewer analysis reveals homozygous loss of exons from 21 to 31 of the ABCC4 gene in 4 PEL-negative individuals (P1, P2, P3, and P4). (B) Schematic representation of the deletion in the ABCC4 gene and Sanger sequencing confirmation of the 67528-pb deletion/18-bp insertion in genomic DNA of PEL-negative individuals. (C) Western blot analyses of ABCC4 in the RBC membranes from PEL-positive (controls 1, 2, and 3) and PEL-negative (P1, P2, and P3) individuals. Immunoblotting was performed with a mouse monoclonal antibody directed against ABCC4. The p55 antibody was used as a loading control.