Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement
The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.
Altered ADAR2 Gene Expression and Altered Editing of PDE8A1 Gene Transcripts in Rheumatoid Arthritis (RA) T Cells
Laxminarayana1, Dama, O'Rourke2, Kenneth, Olorenshaw2, Irene
Rheumatoid Arthritis (RA) is an autoimmune disorder of indeterminate etiology characterized by B and T lymphocyte immune effector dysfunctions. The etiopathogenesis of the abnormal immune response in RA is associated with altered gene expressions. Adenosine to Inosine (A to I) editing is the post-transcriptional site-specific modification of precursor mRNAs catalyzed by the members of ADAR family genes. Such RNA editing plays an important role in the regulation of gene expression and produces phenotypic variability. Therefore, we hypothesize that the altered expression and function of ADARs is a mechanism for the immunopathogenesis of RA.
In the present study, we analyzed expression of ADAR1 and ADAR2 gene transcripts in RA and control T cells by competitive polymerase chain reaction (CPCR). 10 RA subjects and 10 healthy controls were studied. The Cyclic Nucleotide Phosphodiesterase 8A1 (PDE8A1) gene transcripts are edited by ADAR enzymes. Therefore, we assessed the role of altered ADAR2 enzyme expression in editing of PDE8A1 gene transcripts of RA T cells. The base position numbers of PDE8A1 gene transcripts reported here are used from the accession number AK001647. The PDE8A1 gene transcripts from normal and RA T cell samples were amplified and cloned into pCR2.1-TOPO vectors. A total of 100 clones from RA and 100 clones from controls were sequenced using T7 and M13 primers and an automated ABI-377 sequencer.
The results revealed that the mean content of ADAR1 mRNA was 1.84 ±0.41 attomoles/mg total RNA in RA vs 1.79 ± 0.32 attomoles/mg total RNA in controls. The mean content of ADAR2 mRNA was 1.10 ±0.35 attomoles/mg total RNA in RA vs 1.70 ± 0.28 attomoles/mg total RNA in controls (p£0.05). Sequence analyses demonstrated altered A to I editing in the PDE8A1 gene transcripts of RA T cells. There are two hot spots for A to I editing in the PDE8A1 gene transcripts. The first hot spot consists of previously known edited nucleotides 42423 and 42424 and are called site 1. The A to I editing frequency at this site in RA and control samples is 18% and 29% respectively (p£0.001). The second hot spot is found between base positions 42454 and 42457 and called site 2. The A to I editing frequency at the second site was 2% for RA, and 8% for control subjects (p£0.001). In general, A to I editing is impaired in RA T cells compared to normal controls.
It is proposed that, the altered expression of ADAR enzymes tilt the balance of editing machinery and alter editing in RA transcriptome. Such altered editing may contribute to the modulation of gene regulation and ultimately, immune functions in RA patients and play an important role in the initiation and propagation of RA pathogenesis.
This work was supported by National Institutes of Health Grant AR48628 (to D.L).
To cite this abstract, please use the following information:
Laxminarayana, Dama, O'Rourke, Kenneth, Olorenshaw, Irene; Altered ADAR2 Gene Expression and Altered Editing of PDE8A1 Gene Transcripts in Rheumatoid Arthritis (RA) T Cells [abstract]. Arthritis Rheum 2009;60 Suppl 10 :385