Location: Animal Disease ResearchTitle: Genes involved in immune, gene translation and chromatin organization pathways associated with Mycoplasma ovipneumoniae presence in nasal secretions of domestic sheep
|HERNDON, MARIA - Washington State University|
|Taylor, Joshua - Bret|
|BECKER, GABRIELLA - University Of Idaho|
|MURDOCH, BRENDA - University Of Idaho|
Submitted to: PLoS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2021
Publication Date: 7/12/2021
Citation: Mousel, M.R., White, S.N., Herndon, M.K., Herndon, D.R., Taylor, J.B., Becker, G.M., Murdoch, B.M. 2021. Genes involved in immune, gene translation and chromatin organization pathways associated with Mycoplasma ovipneumoniae presence in nasal secretions of domestic sheep. PLoS ONE. https://doi.org/10.1371/journal.pone.0247209.
Interpretive Summary: A contributor to polymicrobial pneumonia in domestic sheep is Mycoplasma ovipneumoniae. Determining if age, breed, sampling time, and year of sample collect impact detection of M. ovipneumoniae will help determine if genomic studies should be conducted. Rambouillet had the lowest compared with Polypay and Suffolk and year-old sheep had the greatest detect amounts of M. ovipneumoniae from nasal mucus. Warmer weather may have had an impact on detection as April and September/October sampling times were higher than February. Breed differences suggested there may be DNA differences affecting M. ovipneumoniae detection. Indeed, testing over 500,000 markers with average M. ovipneumoniae DNA detected in nasal mucus from Polypay, Rambouillet, and Suffolk sheep found regions on chromosomes 4, 6, 7, 9, 10, 15, 17, and 22 were associated. Markers were within or near genes known to have immune functions and change DNA organization. Both these functions would be expected to change when sheep respond to polymicrobial pneumonia. Work is ongoing to identify the exact DNA changes that caused the difference in M. ovipneumoniae detection in nasal mucus in order to develop tools for use by the sheep industry to reduce polymicrobial pneumonia.
Technical Abstract: Mycoplasma ovipneumoniae contributes to polymicrobial pneumonia in domestic sheep. Elucidation of host genetic components to M. ovipneumoniae nasal detections would have the potential to reduce the incidence of pneumonia. Nasal mucosal secretions were collected from 647 sheep from a large US sheep flock. Ewes of three breeds (Polypay n=222, Rambouillet n=321, and Suffolk n=104) ranging in age from one to seven years, were sampled at three different times of the production cycle (February, April, and September/October) over four years (2015 to 2018). The presence and quantity of M. ovipneumoniae was determined using a species-specific qPCR with 3 to 10 unique sampling times per sheep. Breed (P<0.001), age (P<0.024), sampling time (P<0.001), and year (P<0.001) of collection affected log10 transformed M. ovipneumoniae DNA copy number, where Rambouillet had the lowest (P<0.0001) compared with Polypay and Suffolk demonstrating a possible genetic component to detection. Samples from yearlings, April, and 2018 had the highest (P<0.046) detected DNA copy number mean. Sheep genomic DNA was genotyped with the Illumina OvineHD BeadChip. Principal component analysis identified most of the variation in the dataset was associated with breed. Therefore, genome wide association analysis was conducted with a mixed model (EMMAX), with principal components 1 to 6 as fixed and a kinship matrix as random effects. Genome-wide significant (P<9x10-8) SNPs were identified on chromosomes 6 and 7 in the all-breed analysis. Individual breed analysis had genome-wide significant (P<9x10-8) SNPs on chromosomes 4, 7, 9, 10, 15, 17, and 22. Annotated genes near these SNPs are part of immune (ANAPC7, CUL5, TMEM229B, PTPN13), gene translation (PIWIL4), and chromatin organization (KDM2B) pathways. Immune genes are expected to have increased expression when leukocytes encounter M. ovipneumoniae which would lead to chromatin reorganization. Work is underway to narrow the range of these associated regions to identify the underlying causal mutations.