A novel JKA allele, nt561C>A, associated with silencing of Kidd expression.
BACKGROUND
The Jk(a-b-) null phenotype is not common but is more prevalent in Polynesian and Asian persons and appears to be rare in blacks. We determined the molecular basis for Jk(a-b-) in an African American family. DNA testing of samples from random African American, Caucasian, and Brazilian blacks was done to estimate the allele frequency.


METHODS
Standard methods were used for red blood cell (RBC) typing. DNA was isolated from white blood cells, and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and amplification and sequencing of the coding regions of JK were performed by routine molecular methods. A MaeIII PCR-RFLP assay was designed to target the nucleotide (nt) change.


RESULTS
RBCs from the proband typed as Jk(a-b-) and DNA testing indicated JK*A/JK*A. JK sequencing found that the sample was homozygous for nt561C>A change, predicted to encode a premature stop in the protein (187Stop). The altered allele was present in the heterozygous state in three of six siblings. Testing of 500 African American and 100 Caucasian donors from the same region and 500 African American donors from the southern United States found no additional examples. Screening of 1174 Brazilian blacks revealed seven examples: one homozygote and six heterozygotes.


CONCLUSIONS
JK*A (561C>A) is associated with a Kidd-null phenotype in this African American family. The allele was present in approximately one in 168 Brazilian blacks, suggesting that detection of this allele is important to avoid false-positive prediction of Jk(a) status in this population.
National Molecular Blood Group and Platelet Antigen Testing Laboratory, American Red Cross, Philadelphia, PA, USA.
Trina
T
Horn
Lilian
L
Castilho
Joann M
JM
Moulds
Katrina
K
Billingsley
Sunitha
S
Vege
Nanette
N
Johnson
Connie M
CM
Westhoff
D001741:Black or African American; D000483:Alleles; D001483:Base Sequence; D005260:Female; D020868:Gene Silencing; D006801:Humans; D007667:Kidd Blood-Group System / Q000235:genetics*; D008875:Middle Aged; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length
D007667:Kidd Blood-Group System