Association between anti-ZnT8 autoantibody specificities and SLC30A8 Arg325Trp variant in Japanese patients with type 1 diabetes.
OBJECTIVE
We analysed the association between humoral autoreactivity to zinc transporter-8 (ZnT8) and the SLC30A8 rs13266634 polymorphism (Arg325Trp), which is located at the most distal loop in the ZnT8 protein.


METHODS
Autoantibodies to ZnT8 were determined by RIA in 270 patients with type 1 diabetes using ZnT8 carboxy-terminal constructs (amino acids 268-369) carrying 325Trp(CW) and 325Arg(CR) and a hybrid construct (CW-CR). Forty-four ZnT8 autoantibody-positive sera with genomic DNA were used to examine the association between reactivity to ZnT8 constructs and the rs13266634 genotype.


RESULTS
Seventy-five patients reacted to the CW-CR hybrid construct, whereas 37 and 36 patients reacted to the CW and CR constructs, respectively. All sera positive for either CW or CR autoantibodies were positive for CW-CR autoantibodies. Among 19 patients with a 325Arg(CC) genotype, 5% had CW-specific autoantibodies, 42% had CR-specific autoantibodies and 32% had dual reactivity. Conversely, 73% of 15 patients with the 325Trp(TT) genotype had CW-specific autoantibodies, no patients had CR-specific autoantibodies and 13% had dual reactivity. Nine of the ten patients (90%) with the CT genotype reacted with either CR or CW constructs. The titre of CR autoantibodies in patients carrying the C allele was significantly higher than that in TT homozygotes (p < 0.0001). In contrast, the titre of CW autoantibodies in patients carrying a T allele was significantly higher than that in CC homozygotes (p < 0.005). No evidence of an association between rs13266634 and type 1 diabetes was observed.


CONCLUSIONS
These results indicate that variant residue at amino acid 325 is a key determinant of humoral autoreactivity to ZnT8 and that the SLC30A8 genotype is an important determinant of autoantibody specificity.
Department of Metabolism/Diabetes and Clinical Nutrition, Nagasaki University Hospital of Medicine and Dentistry, 1-7-1 Sakamoto, Nagasaki, 852-8501, Japan. eijikawa@nagasaki-u.ac.jp
E
E
Kawasaki
M
M
Uga
K
K
Nakamura
G
G
Kuriya
T
T
Satoh
K
K
Fujishima
M
M
Ozaki
N
N
Abiru
H
H
Yamasaki
J M
JM
Wenzlau
H W
HW
Davidson
J C
JC
Hutton
K
K
Eguchi
D000293:Adolescent; D000328:Adult; D000368:Aged; D000918:Antibody Specificity / Q000276:immunology*; D001120:Arginine / Q000235:genetics / Q000378:metabolism; D044466:Asian People / Q000235:genetics*; D001323:Autoantibodies / Q000276:immunology*; D027682:Cation Transport Proteins / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D000075703:Zinc Transporter 8
D001323:Autoantibodies; D027682:Cation Transport Proteins; C492522:SLC30A8 protein, human; D000075703:Zinc Transporter 8; D001120:Arginine