Grant: 18-033R
Project Title: Immune gene and pathogen drivers of fibropapillomatosis in Florida juvenile green and loggerhead sea turtles: Year 2
Project Manager: Dr. Anna E. Savage
Organization: University of Central Florida (Research and Educational Institute)
Grant Amount: $21,966.00
Completion Date: 2019-12-06
Summary: Maintaining genetic diversity is critical for the long-term survival and persistence of natural populations, yet the inclusion of population genetic analyses into conservation and management decisions is lacking for many taxa. Due to the widespread occurrence and negative consequences of the infectious benign tumor disease fibropapillomatosis (FP), sea turtles are a group that could benefit dramatically from more and better genetic studies relating disease dynamics to genetic diversity and candidate resistance genes. During this project, we will investigate the functional genetic factors potentially influencing FP susceptibility within and among species by continuing to sequence a wider array of MHC genes in larger sample sizes of C. mydas and C. caretta. MHC genes code for immune suveillance molecules that identify pathogens and flag them for destruction. Because higher levels of MHC variation allow more pathogens to be recognized, MHC genes are the most diverse genes in the vertebrate genome. Due to this high variability and important role in immunity, MHC genes are ideal markers for measuring genetic health of populations, particularly in the context of disease. Our goal in year 2 is to generate a catalogue of class I and II alleles and frequencies in C. mydas and C. caretta to establish definitive links between FP and particular alleles that can be used for long-term monitoring of population trajectories and genetic health.
Results: To fully analyze the relationship between class I MHC diversity, immune function, herpesivurs infection, and FP, we employed a model selection appraoch using generalized linear models. Due to the high number of alleles, we focused our analysis on MHC supertypes (functional groups of alleles, inferred by an analysis of amino acid properties) as well as alleles. We find that several alleles, and one supertype, are consistent predictors of FP. However, herpesvirus and white blood cell counts are not explanatory. We are currently preparing a manuscript describing these results that we aim to submit to the journal Evolutionary Applications before the end of this year. Our results are exciting in that they suggest simple genetic biomarkers exist for FP resistant individuals. If we find continued support for this pattern with more data, especially gene expression data that more explicitly relate to genome function, these biomarkers could be easily implemented to screen turtles and to assess their FP risk, as well as to better understand why FP severity is variable across regions and sea turtle species.