The copy numbers of candidate genes, signal regulatory protein beta 1 gene (SIRPB1) and transmembrane protein 91 gene (TMEM91), were quantified for each subject using the real-time PCR method.
According to a genome-wide association study based on the comparison of patients and controls, two immune-related genes, SIRPB1 and TMEM91, were selected as candidate genes, which were located on the chromosomal regions 20p13 and 19q13.2, respectively.
The distributions of SIRPB1 and TMEM91 CNVs in AITD patients and controls are summarized in Table 3.
The copy number of SIRPB1 and TMEM91 for 158 AITD patients was used to explore the relationship between the CNVs of the two genes.
Analysis of multivariate logistic regression revealed that high urinary iodine levels (odds ratio (OR) = 1.94, p = 0.031) and SIRPB1 CNVs (OR = 3.51, p = 0.016) were risk factors for AITD (Table 4).
As shown in Table 5, there were no significant associations between urinary iodine level and the CNVs of SIRPB1 and TMEM91.
The protein encoded by SIRPB1 is a member of the signal regulatory protein family and also belongs to the immunoglobulin superfamily .
Nevertheless, there existed a significant correlation between CNVs of TMEM91 and SIRPB1, indicating that the small study sample size may be the reason for these nonsignificant findings.
The present study indicated that the CNV of the SIRPB1 gene and an excess of iodine were risk factors for AITD, but an association with the occurrence of AITD was not discovered.