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Description
There are several challenges to accurately inferring levels of transcription using RNA-sequencing (RNA-seq) data, including detecting and correcting for reference genome mapping bias. One potential confounder of RNA-seq analysis results from the application of a standardized pipeline to samples of different sexes in species with chromosomal sex determination. The homology

There are several challenges to accurately inferring levels of transcription using RNA-sequencing (RNA-seq) data, including detecting and correcting for reference genome mapping bias. One potential confounder of RNA-seq analysis results from the application of a standardized pipeline to samples of different sexes in species with chromosomal sex determination. The homology between the human X and Y chromosomes will routinely cause mismapping to occur, artificially biasing estimates of sex-biased gene transcription. For this reason we tested sex-specific mapping scenarios in humans on RNA-seq samples from the brains of 5 genetic females and 5 genetic males to assess how inferences of differential gene expression patterns change depending on the reference genome. We first applied a mapping protocol where we mapped all individuals to the entire human reference genome (complete), including the X and Y chromosomes, and computed differential expression between the set of genetic male and genetic female samples. We next mapped the genetic female samples (46,XX) to the human reference genome with the Y chromosome removed (Y-excluded) and the genetic male samples (46, XY) to the human reference genome (including the Y chromosome), but with the pseudoautosomal regions of the Y chromosome hard-masked (YPARs-masked) for the two sex-specific mappings. Using the complete and sex-specific mapping protocols, we compared the differential expression measurements of genetic males and genetic females from cuffDiff outputs. The second strategy called 33 additional genes as being differentially expressed between the two sexes when compared to the complete mapping protocol. This research provides a framework for a new standard of reference genome mappings to correct for sex-biased gene expression estimates that can be used in future studies.
ContributorsBrotman, Sarah Marie (Author) / Wilson Sayres, Melissa (Thesis director) / Crook, Sharon (Committee member) / Webster, Timothy (Committee member) / School of Life Sciences (Contributor) / School of Mathematical and Natural Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description

Hepatocellular Carcinoma (HCC) is one of the main types of liver cancer accounting for 75% of cases and is the second deadliest cancer worldwide. Chronic Hepatitis B (HBV) and Hepatitis C (HCV) remain one of the most important global risk factors and account for 80% of all HCC cases. HCC

Hepatocellular Carcinoma (HCC) is one of the main types of liver cancer accounting for 75% of cases and is the second deadliest cancer worldwide. Chronic Hepatitis B (HBV) and Hepatitis C (HCV) remain one of the most important global risk factors and account for 80% of all HCC cases. HCC also exhibits sex-differences with significantly higher incidence and worse prognosis in males. The mechanistic basis of these sex-differences is poorly understood. To identify genes and pathways that are sex-differentially expressed in viral-mediated HCC, we performed differential expression analysis on tumor vs. tumor adjacent samples that were stratified based on sex, viral etiology, and both. The differentially expressed genes were then used in a pathway enrichment analysis to identify potential pathways of interest. We found differentially expressed genes in both sexes and both etiologies. 65 genes were unique to females and 184 genes unique to males. 381 genes are unique to HBV and 195 genes are unique to HCV. We also found pathways that were significantly enriched by the differentially expressed genes. Ten pathways unique to the female tumor tumor-adjacent comparison and a majority of those pathways were a part of the cell cycle. Four enriched pathways unique to male tumor tumor-adjacent and three of them were a part of the immune system. There were no pathways unique to either etiology, but seven pathways shared by both etiologies. Two were a part of the cell cycle and one involved lipid metabolism. These differentially expressed genes and significant pathways are potential targets for individualized therapeutics and diagnostics for HCC.

ContributorsJorgensen, Annika (Author) / Wilson, Melissa (Thesis director) / Buetow, Kenneth (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor) / Department of Physics (Contributor)
Created2023-05