Identification of a SLC29A1-null mutation responsible for the Atnull blood type in a family of European ancestry. (A) Pedigree of the family of the proband (arrow); black-filled symbols represent individuals with the Atnull blood type; N/D, no data. (B) Detail of SLC29A1 sequencing in the proband, her parents, and siblings, showing the segregation of the c.589+1G>C mutation in her family; reference sequence (NC_000006) is indicated at the top; the highly conserved dinucleotide GT at the 5′ end of intron 6-7 is underlined; and of note, the c.589+1G>C mutation is associated with the major allele of rs45458701 and the minor allele of rs45573936 in the proband’s family. (C) Exon-intron diagram of human SLC29A1 gene (based on NM_004955) highlighting the location of the splice mutation c.589+1G>C found in the proband’s family (red) and 5 other loss-of-function mutations found in the heterozygous state in the Exome Aggregation Consortium data (black); exons are numbered 1 to 13. (D) The SLC29A1-encoded nucleoside transporter ENT1 is absent in the red cells of the proband. Red cells membranes were prepared from the proband (lane 2) and 2 controls (lanes 1 and 3), resolved by polyacrylamide gel electrophoresis under reducing conditions without heat denaturation, and immunoblotted with an antibody raised against a peptide from the extreme N terminus of the ENT1 transporter (upper); as a control, the western blot membrane was reprobed with an antibody to the ABCG2 transporter (lower). (E) X-ray views of the left hand of the proband (V.1; 49 y) and the right hand of her brother (V.2, 37 y), showing the presence of small calcifications around the metacarpo- and interphalangeal joints.
