Identification and inheritance of the Co-null mutation. (A) Direct sequence analysis of normal AQP1 (top) and AQP1 Co-null (bottom) cDNAs displaying a mutation in the codon 192 of NPA motif. Primers used for PCR: 5′-TCGGGCCAGGGCCTGGGCAT-3′ (sense, nucleotides 441 to 460) and 5′-CTACAGTATGGATTTCACCC-3′ (anti-sense, 911 to 930). (B): Inheritance of the Co-null mutation in the propositus (arrow) family. Genomic DNA from blood cells of the different members of the Colton-null family were isolated and direct sequence analysis was performed with the primers: 5′-CCCCTCCCTCTGTTTCTTTCCC-3′ (sense, intron B) and 5′-CTACAGTATGGATTTCACCC-3′ (anti-sense, 911 to 930 exon 4).