Traditionally, autosomal genes, when expressed, are assumed to express both alleles equally. Exceptions to this tenet include genes for which a specific genotypic polymorphism controls expression level, as well as genes for which monoallelic expression is epigenetically dictated. In this work, we discovered and characterized allele-specific gene expression in a variety of tissues using multiple techniques. We used cell lines and fresh tissue from reciprocal crosses of F1 heterozygous mice and the homozygous parental strains. We relied on a variety of high-throughput genomic techniques including RNA-Seq and DNA SNP-arrays to examine multiple types of allele-specific expression. We searched for novel examples of random autosomal monoallelic expression (RMAE) by using DNA SNP-arrays and cDNA from lymphoblast and fibroblast clonal cell lines of heterozygous mice. We found that of the approximately 1,350 autosomal genes we assessed, over 10% showed evidence of RMAE in at least one cell type. This allele-specific expression was stable over long periods in cell culture and encompassed a variety of gene types, some of which also exhibit RMAE in human clonal lines. Additionally, for a subset of RMAE genes, there seemed to be preferential inactivation of one allele; this monoallelic expression was still considered random, as from clone to clone the gene could be expressed either monoallelically or biallelically. In a second set of experiments we developed an analysis pipeline to examine RNASeq data for allele-specific expression. Using a pilot data set, we assessed the murine liver for parent-of-origin monoallelic expression, examining both known and candidate novel imprinted genes. We observed imprinted monoallelic expression in the adult liver for some, but not all, imprinted genes that have been reported in studies of embryonic tissue. The results suggest that there are few, if any, novel imprinted genes to be discovered in the mouse liver. This pilot data set also allowed examination of the genetic basis of allele specific gene expression. In keeping with recent reports, we found evidence for genetically based allele-specific expression, ranging from mild to greater than 4-fold allelic imbalance. We examined the extent to which this allelic imbalance correlated with total expression levels in the parental strains.
| Identifer | oai:union.ndltd.org:harvard.edu/oai:dash.harvard.edu:1/10288325 |
| Date | January 2012 |
| Creators | Zwemer, Lillian |
| Contributors | Chess, Andrew |
| Publisher | Harvard University |
| Source Sets | Harvard University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis or Dissertation |
| Rights | closed access |
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