CD33 mRNA Has Elevated Expression Levels in the Leukocytes of Peripheral Blood in Patients with Late-Onset Alzheimer's Disease

Background/Aims: In despite of conflicting results among different ethnic groups, the rs3865444 of CD33 gene has previously been identified as a risk factor for late-onset Alzheimer's disease (LOAD).This study was aimed to evaluate the association between rs3865444 SNP with LOAD occurrence, and to investigate whether CD33 mRNA expression will change in the leukocytes of peripheral blood in LOAD patients. Methods: The rs3865444 polymorphism was genotyped in 233 LOAD and 238 control subjects using the Tetra-ARMS-PCR method. CD33 mRNAs expression in leukocytes were assessed and analyzed using the real-time qPCR method. We used in silico approach to analyze potential effects imparted by rs3865444 polymorphism in LOAD pathogenesis. Results: Our results show a significant increase in CD33 mRNA expression levels in white blood cells of LOAD patients, however, the association between CD33 rs3865444 polymorphism and LOAD was found to be not significant. We also noticed that LOAD patients with the C/A genotype had higher CD33 mRNA levels in their peripheral blood than those of the control group. Conclusions: rs3865444, located upstream of the 5 ' CD33 coding region, might positively influence CD33 mRNAs expression in leukocytes of LOAD versus healthy people. This is likely to happen through interfering rs3865444 (C) with the functional activity of several other transcription factors given that rs3865444 is in linkage disequilibrium with other functional polymorphisms in this coding region according to an in silico study. We propose that CD33 mRNAs elevation in peripheral immune cells - as a potential biomarker in LOAD - is related to peripheral immune system impairment.

Automated summary

This study evaluated the association between rs3865444 SNP of CD33 gene and late-onset Alzheimer's disease (LOAD) occurrence, as well as the change in CD33 mRNA expression in leukocytes of LOAD patients. Results showed increased CD33 mRNA levels in white blood cells of LOAD patients, but the association between rs3865444 polymorphism and LOAD was not significant. The study suggests that CD33 mRNA elevation in peripheral immune cells in LOAD patients may be related to peripheral immune system impairment.