To identify genes that may participate in the pathophysiology of Sjögren's syndrome (SS), the technique of differential display was applied to labial minor salivary gland (MSG) biopsy samples.
Total RNA was isolated from MSG biopsy samples from a woman with primary SS and a control subject, and the differential display protocol with 8 different random oligonucleotide primers was performed. One particular differentially expressed fragment showed 98% homology with the cysteine-rich secretory protein 3 (CRISP-3) gene. The result was verified by reverse transcription-polymerase chain reaction (RT-PCR) with messenger RNA (mRNA) samples from MSG biopsy tissues obtained from 4 women with primary SS. A CRISP-3 RNA probe was synthesized for in situ hybridization of 7 MSG biopsy samples from patients with primary SS. In an attempt to interpret the expression of CRISP-3, normal peripheral blood lymphocytes (PBLs) were activated in vitro at different time points and assayed for CRISP-3 expression. Finally, B cells were transfected with the coding region of CRISP-3 and monitored for the up-regulation of different B cell activation markers.
The CRISP-3 gene was detected by RT-PCR in all SS patients tested. Mainly the mononuclear cells infiltrating the MSGs of patients expressed CRISP-3 mRNA. In addition, CRISP-3 was detected by RT-PCR between 30 minutes and 6 hours in phorbol myristate acetate-activated normal PBLs, while staurosporine inhibited this expression. CRISP-3-transfected B cells exhibited an up-regulation in CD25 surface expression.
The CRISP-3 gene is identified as a novel early response gene that may participate in the pathophysiology of the autoimmune lesions of SS.