Analysis of Transcript Expression and Core Promoter DNASequences of Brain, Adipose Tissues and Testis in Human andFruit Fly

Abstract

Gene expression plays a fundamental role in defining the characteristics of living organisms.To deepen our understanding of tissue-specific gene expression, we analyzed transcriptvariant enrichment across different tissues in human and Drosophila melanogaster. Datasetsare widely accessible for both of these organisms. Given the substantial volume of availableinformation, we have focused our interest on three fundamentally distinct tissues: thebrain, where both neuronal and glial cells exhibit a relatively high cellular surface area,thus requiring a large amount of lipids; the adipose tissue, which is well-known forlipid storage; and the testis, which contains a massive number of developing spermatidswith high membrane requirement. These three organs have fundamental differences intheir structure and function yet share some common features; they all have lipid-richcells and have special metabolic pathways. Most studies focus on gene expression, andtranscript level analyses are less common; therefore, we aimed to characterize the transcriptprofiles of these tissues and examine evolutionarily conserved pathways between humansand Drosophila. Additionally, we analyzed the flanking sequences of transcriptionalstart sites of tissue-enriched transcripts. Our findings suggest that Drosophila tissuesexhibit more distinct regulation of gene expression in individual tissues (weaker correlationin expression and variable nucleotide content in core promoter), whereas human geneexpression is more generalized, likely relying more heavily on distal regulatory elementsfor tissue-specific expression. Through network analysis, summarizing tissue specificity,physical interactions, and orthologue data, we identified shared central pathways amongthese tissues. A relatively large network was observable in the testis, where the ubiquitinproteasome system, various kinases and transcription factors showed central position inboth organisms. Additionally, we highlighted the evolutionary potential of highly enrichedtestis-specific transcripts. This work provides valuable insights into the mechanismsunderlying tissue-specific gene expression and evolutionary conservation.