Natural allelic variation of the IL-21 receptor modulates ischemic stroke infarct volume
Han Kyu Lee, … , Donald C. Lo, Douglas A. Marchuk
Han Kyu Lee, … , Donald C. Lo, Douglas A. Marchuk
Published July 11, 2016
Citation Information: J Clin Invest. 2016;126(8):2827-2838. https://doi.org/10.1172/JCI84491.
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Natural allelic variation of the IL-21 receptor modulates ischemic stroke infarct volume

Abstract

Risk for ischemic stroke has a strong genetic basis, but heritable factors also contribute to the extent of damage after a stroke has occurred. We previously identified a locus on distal mouse chromosome 7 that contributes over 50% of the variation in postischemic cerebral infarct volume observed between inbred strains. Here, we used ancestral haplotype analysis to fine-map this locus to 12 candidate genes. The gene encoding the IL-21 receptor (Il21r) showed a marked difference in strain-specific transcription levels and coding variants in neonatal and adult cortical tissue. Collateral vessel connections were moderately reduced in Il21r-deficient mice, and cerebral infarct volume increased 2.3-fold, suggesting that Il21r modulates both collateral vessel anatomy and innate neuroprotection. In brain slice explants, oxygen deprivation (OD) activated apoptotic pathways and increased neuronal cell death in IL-21 receptor–deficient (IL-21R–deficient) mice compared with control animals. We determined that the neuroprotective effects of IL-21R arose from signaling through JAK/STAT pathways and upregulation of caspase 3. Thus, natural genetic variation in murine Il21r influences neuronal cell viability after ischemia by modulating receptor function and downstream signal transduction. The identification of neuroprotective genes based on naturally occurring allelic variations has the potential to inform the development of drug targets for ischemic stroke treatment.

Authors

Han Kyu Lee, Sehoon Keum, Huaxin Sheng, David S. Warner, Donald C. Lo, Douglas A. Marchuk

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Figure 5

Functional consequences of IL-21R are altered by a second IL-21R coding difference between inbred mouse strains.

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Functional consequences of IL-21R are altered by a second IL-21R coding ...
(A) Alignments of amino acid sequences are compared across different inbred mouse strains and other mammalian species. The valine (V) found at amino acid position 200 (rs33006504) in B6, FVB, and NOD mouse strains is well conserved in mammalian species except inbred mouse strains BALB/c and SWR showing the methionine (M) at the amino acid position. This V200M change is predicted to be functionally damaging to the protein with in silico analysis (PolyPhen-2 score: 0.789). (B) Western blots were performed to detect levels of both p-STAT3 and STAT3 in explanted brain slices of 2 inbred mouse strains, B6 and BALB/c, as well as 2 Civq1 congenic lines, C.B6–Civq1–6 and C.B6–Civq1–7, 1 hour after treatment with either vehicle or recombinant murine IL-21 (50 ng/ml). (C) Levels of p-STAT3 were determined. Level of total STAT3 was used for normalization. Experiments were performed 3 times using 3 mice per mouse strain for each experiment. Values represent mean ± SEM. *P < 0.05; **P < 0.01; ***P < 0.001 vs. B6 vehicle treatment, 2-tailed Student’s t test. (D) Graph shows the infarct volume. Total numbers of animals for C.B6–Civq1–6 and C.B6–Civq1–7 are 29 and 30, respectively. Representative images are shown in Supplemental Figure 13, F and G. Values represent mean ± SEM. **P < 0.01 vs. C.B6–Civq1–6, 2-tailed Student’s t test.