Highly consistent MHC-I gene expression patterns across life-stages, generations and tissues in a songbird
Major Histocompatibility Complex class I (MHC-I) molecules are key components of adaptive immunity and encoded by a multigene family which has expanded considerably in songbirds (Passeriformes) compared to other bird orders. A large proportion of the MHC-I genes are expressed, but the functional relevance of the high MHC-I diversity (number of alleles per individual) remains poorly understood in songbirds. We took advantage of our long-term monitored population of great reed warblers Acrocephalus arundinaceus to study patterns of MHC-I gene expression in blood during individuals' lifetime and across generations. The expressed diversity increased linearly with the genomic MHC-I diversity; however, most alleles were expressed at low levels, with only a handful showing moderate to high expression in each individual. MHC-I expression patterns in blood were highly consistent over an individual's lifetime, between parents and offspring and among siblings, and was also strongly correlated with expression in other tissues. We envision that moderately to highly expressed MHC-I genes play a more important role in antigen presentation than lowly expressed genes. Genes that are currently lowly expressed may become highly expressed in the future or contribute with genetic variation to highly expressed genes through gene conversion.
Major Histocompatibility Complex class I (MHC-I) molecules are key components of adaptive immunity and encoded by a multigene family which has expanded considerably in songbirds (Passeriformes) compared to other bird orders. A large proportion of the MHC-I genes are expressed, but the functional relevance of the high MHC-I diversity (number of alleles per individual) remains poorly understood in songbirds. We took advantage of our long-term monitored population of great reed warblers Acrocephalus arundinaceus to study patterns of MHC-I gene expression in blood during individuals' lifetime and across generations. The expressed diversity increased linearly with the genomic MHC-I diversity; however, most alleles were expressed at low levels, with only a handful showing moderate to high expression in each individual. MHC-I expression patterns in blood were highly consistent over an individual's lifetime, between parents and offspring and among siblings, and was also strongly correlated with expression in other tissues. We envision that moderately to highly expressed MHC-I genes play a more important role in antigen presentation than lowly expressed genes. Genes that are currently lowly expressed may become highly expressed in the future or contribute with genetic variation to highly expressed genes through gene conversion.
Lund University