Identification of candidate genes for Sjögren's syndrome using MRL/lpr mouse model of Sjögren's syndrome and cDNA microarray analysis.

Sjögren's syndrome is a chronic autoimmune disease characterized by focal lymphocytic infiltration of lacrimal and salivary glands, but the precise mechanism of this syndrome is poorly understood. To clarify the mechanism of onset and progression of Sjögren's syndrome, it is necessary to identify Sjögren's syndrome-related genes. For this purpose, we used MLR/MpJ-lpr/lpr (MRL/lpr) mouse as a model of human secondary Sjögren's syndrome and analyzed specific mRNA expression pattern in MRL/lpr mouse salivary glands by in-house cDNA microarray. Among arrayed 2304 genes, 13 genes were isolated as highly expressed genes in MRL/lpr mouse salivary gland in comparison with MRL/MpJ-+/+ (MRL/+) mouse tissue. Subsequently, we performed RT-PCR analysis and confirmed the high expression level of nine genes; caspase3, Ly-6C.2, vimentin, Mel-14 antigen, cathepsin B, mpt1, Laptm5, Gnai2 and UCP2. Five of the nine genes have already been identified in patients with Sjögren's syndrome or mice models of the syndrome, but the remaining four genes; mpt1, Laptm5, Gnai2, and UCP2 have not been reported previously as Sjögren's syndrome-related genes. Although, further experiments are necessary to examine the relationship between these four genes and Sjögren's syndrome, our system of mouse model of Sjögren's syndrome combined with in-house cDNA microarray is suitable for the isolation of Sjögren's syndrome-related genes.