Monocyte Gene Expression Analysis in Psychiatric and Metabolic Disorders

CD14⁺ monocytes were isolated from the frozen PBMCs using a magnetic cell sorting system (Miltenyi Biotec, Germany) resulting in a purity of monocytes >95%. RNA was isolated from the purified monocytes, and 1 μg of RNA was reverse transcribed using the cDNA high-capacity cDNA Reverse Transcription Kit (Applied Biosystems, Carlsbad, CA, USA). The cDNA was used in quantitative polymerase chain reaction (qPCR) to determine gene expression using the comparative threshold (CT) cycle method (32 ). qPCR was performed using a TaqMan Universal PCR mastermix and TaqMan probes (Applied Biosystems). Gene expression was normalized to expression of housekeeping gene ABL1, and the resulting ΔCT values were used for further analyses.
Genes of interest were selected based on previous findings of abnormally expressed genes in patients with BD (4 (link), 5 (link), 11 (link)), MDD (31 (link)), type 2 diabetes (23 (link)), and systemic autoimmune diseases [the IFN-induced inflammatory genes (33 (link))], and known to be involved in major inflammatory or immune activation pathways in monocytes and macrophages. We selected the most consistently over expressed genes. A list of included genes is given in Table S1 in Supplementary Material.