Hematopoietic not systemic impairment of Roquin expression accounts for intestinal inflammation in Roquin-deficient mice

Abstract

Roquin, an E3 ligase, is involved in curtailing autoimmune pathology as seen from studies using mice with mutated (Rc3h1san/san) or disrupted (Rc3h1gt/gt) Rc3h1 gene. The extent to which intestinal immunopathology is caused by insufficient Roquin expression in the immune system, or by Roquin impairment in non-hematopoietic cells, has not been determined. Using bone marrow cells from Rc3h1gt/gt mice transferred into irradiated normal mice (Rc3h1gt/gt → NL chimeras), we show that inflammation developed in the small intestine, kidney, lung, liver, and spleen. Proinflammatory cytokine levels were elevated in lamina propria lymphocytes (LPLs). Inflammation in the liver was accompanied by areas of hepatocyte apoptosis. Lung inflammation consisted of an influx of both T cells and B cells. Small intestinal LPLs had increased numbers of CD44hi, CD62Llo, KLRG1+, ICOS+ short-lived effector cells, indicating an influx of activated T cells. Following oral infection with L. monocytogenes, Rc3h1gt/gt → NL chimeras had more liver pathology and greater numbers of bacteria in the Peyer's patches than NL → NL chimeras. These findings demonstrate that small intestinal inflammation in Rc3h1san/san and Rc3h1gt/gt mice is due to a failure of Roquin expression in the immune system and not to insufficient systemic Roquin expression.

MicroRNA signatures differentiate Crohn’s disease from ulcerative colitis

“…In a subset of CD patients, RC3H1 expression was reduced in statistically significant manner in a subset of the endoscopically involved versus endoscopically uninvolved matched colony biopsy pairs. In mouse models deficient for Rc3h1 , either the sanroque missense mutation ( Rc3h1 san/san ) mouse or a genetrap knockout ( Rc3h1 gt/gt ) mouse, an acute small intestinal inflammation develops among other phenotypes [ 50 , 61 , 62 ]. Roquin-1 is involved in the post-transcriptional regulation of mRNA.…”

Roquin—a multifunctional regulator of immune homeostasis

“…Activation-induced cell death and the proportional numbers of CD4 + CD25 + Tregs remain unaltered in sanroque mice ( 2 ). Those changes are T cells autonomous as seen from studies of mixed bone marrow chimeras ( 2 ), and in radiation chimaeras using bone marrow from Roquin-deficient mice ( 33 ).…”

“…At odds with those findings are studies in which Rc3h1 −/− mice were generated by insertion of a gene-trap into intron 1 ( Rc3h1 gt/gt mice), which resulted in a phenotype more typical of that seen in sanroque animals ( 33 , 36 ). Although Rc3h1 gt/gt mice had caudal spine deformity and poor post-birth survival ( 36 ) similar to that of Rc3h1 −/− and Rc3h2 −/− mice ( 11 , 52 ), Rc3h1 gt/gt mice developed extensive inflammation in the small intestine, though not in the colon, and had a destructive inflammatory response in the kidney, lungs, liver, and spleen ( 33 ) that was reminiscent of sanroque mice. That phenotype was similarly retained in chimeric mice made from bone marrow of Rc3h1 gt/gt mice injected into irradiated syngeneic animals ( 33 ), confirming that hematopoietic and not systemic disruption of Roquin-1 expression was the primary factor responsible for the development of immunopathology.…”

“…Although Rc3h1 gt/gt mice had caudal spine deformity and poor post-birth survival ( 36 ) similar to that of Rc3h1 −/− and Rc3h2 −/− mice ( 11 , 52 ), Rc3h1 gt/gt mice developed extensive inflammation in the small intestine, though not in the colon, and had a destructive inflammatory response in the kidney, lungs, liver, and spleen ( 33 ) that was reminiscent of sanroque mice. That phenotype was similarly retained in chimeric mice made from bone marrow of Rc3h1 gt/gt mice injected into irradiated syngeneic animals ( 33 ), confirming that hematopoietic and not systemic disruption of Roquin-1 expression was the primary factor responsible for the development of immunopathology. The basis for the differences in the immunological findings of Rc3h1 −/− , Rc3h2 −/− , and Rc3h1 gt/gt mice is unclear; however, it could reflect variations in the methods used to render mice Roquin deficient.…”

ROQUIN signalling pathways in innate and adaptive immunity

“…In chimeric mice with a reconstituted immune system derived from stem cells of sanroque or gt (gene trap) mice harboring a disrupted Rc3h1 allele, spontaneous SLEC expansion leads to severe autoinflammatory bowel disorder with elevated expression of proinflammatory cytokines such as IFN‐γ and TNF‐α . These studies lend support to the relevance of CD8 + T‐cell regulation by ROQUIN in T‐cell‐mediated pathology.…”