Synaptogyrin-2 influences replication of Porcine circovirus 2

Authors

Lianna R. Walker, University of Nebraska–LincolnFollow
Taylor B. Engle, University of Nebraska - Lincoln
Hiep Vu, University of Nebraska-lincolnFollow
Emily R. Tosky, University of Nebraska - Lincoln
Dan J. Nonneman, USDA, Agricultural Research Service
Timothy P. L. Smith, USDA, Agricultural Research ServiceFollow
Tudor Borza, Dalhousie University
Thomas E. Burkey, University of Nebraska - LincolnFollow
Graham S. Plastow, University of Alberta
Stephen D. Kachman, University of Nebraska-LincolnFollow
Daniel C. Ciobanu, University of Nebraska-LincolnFollow

ORCID IDs

0000-0001-8073-7843

0000-0002-2527-6551

0000-0002-3774-3110

0000-0003-0506-513X

0000-0002-7301-1339

Date of this Version

2018

Citation

PLoS Genet 14(10): e1007750

Comments

Open access

https://doi.org/10.1371/journal.pgen.1007750

Abstract

Porcine circovirus 2 (PCV2) is a circular single-stranded DNA virus responsible for a group of diseases collectively known as PCV2 Associated Diseases (PCVAD). Variation in the incidence and severity of PCVAD exists between pigs suggesting a host genetic component involved in pathogenesis. A large-scale genome-wide association study of experimentally infected pigs (n = 974), provided evidence of a host genetic role in PCV2 viremia, immune response and growth during challenge. Host genotype explained 64% of the phenotypic variation for overall viral load, with two major Quantitative Trait Loci (QTL) identified on chromosome 7 (SSC7) near the swine leukocyte antigen complex class II locus and on the proximal end of chromosome 12 (SSC12). The SNP having the strongest association, ALGA0110477 (SSC12), explained 9.3% of the genetic and 6.2% of the phenotypic variance for viral load. Dissection of the SSC12 QTL based on gene annotation, genomic and RNA-sequencing, suggested that a missense mutation in the SYNGR2 (SYNGR2 p.Arg63Cys) gene is potentially responsible for the variation in viremia. This polymorphism, located within a protein domain conserved across mammals, results in an amino acid variant SYNGR2 p.63Cys only observed in swine. PCV2 titer in PK15 cells decreased when the expression of SYNGR2 was silenced by specific-siRNA, indicating a role of SYNGR2 in viral replication. Additionally, a PK15 edited clone generated by CRISPR-Cas9, carrying a partial deletion of the second exon that harbors a key domain and the SYNGR2 p.Arg63Cys, was associated with a lower viral titer compared to wildtype PK15 cells (>24 hpi) and supernatant (>48hpi)(P < 0.05). Identification of a non-conservative substitution in this key domain of SYNGR2 suggests that the SYNGR2 p.Arg63Cys variant may underlie the observed genetic effect on viral load.