Human gene expression variability and its dependence on methylation and aging

• Published in: BMC genomics Vol. 20; no. 1; pp. 941 - 19
• Main Authors: Bashkeel, Nasser, Perkins, Theodore J., Kærn, Mads, Lee, Jonathan M.
• Format: Journal Article
• Language: English
• Published: London BioMed Central 07.12.2019; BioMed Central Ltd; BMC
• Subjects: Age Factors; Aging; Aging (natural); Aging - genetics; Animal Genetics and Genomics; Biochemistry; Biomedical and Life Sciences; Brain Chemistry; Breast; Breast - chemistry; Cadaver; Classification; CpG Islands; DNA Methylation; Epigenesis, Genetic; Essentiality; Expression variability; Female; Gene expression; Gene Expression Profiling - methods; Gene Expression Regulation; Gene polymorphism; Gene Regulatory Networks; Genes; Genetic aspects; Genetic polymorphisms; Genetic research; Genetic variability; Genomics; Human and rodent genomics; Human populations; Humans; Life Sciences; Male; Methylation; Microarrays; Microbial Genetics and Genomics; Novels; Organ Specificity; Phenotype; Plant Genetics and Genomics; Polymorphism; Population; Populations; Proteomics; Regression analysis; Research Article; Sampling error; Sex; Tissue specificity; Tissues; Variability; Tissue specificity; Aging; Methylation; Essentiality; Expression variability
• ISSN: 1471-2164; 1471-2164
• DOI: 10.1186/s12864-019-6308-7

Background Phenotypic variability of human populations is partly the result of gene polymorphism and differential gene expression. As such, understanding the molecular basis for diversity requires identifying genes with both high and low population expression variance and identifying the mechanisms underlying their expression control. Key issues remain unanswered with respect to expression variability in human populations. The role of gene methylation as well as the contribution that age, sex and tissue-specific factors have on expression variability are not well understood. Results Here we used a novel method that accounts for sampling error to classify human genes based on their expression variability in normal human breast and brain tissues. We find that high expression variability is almost exclusively unimodal, indicating that variance is not the result of segregation into distinct expression states. Genes with high expression variability differ markedly between tissues and we find that genes with high population expression variability are likely to have age-, but not sex-dependent expression. Lastly, we find that methylation likely has a key role in controlling expression variability insofar as genes with low expression variability are likely to be non-methylated. Conclusions We conclude that gene expression variability in the human population is likely to be important in tissue development and identity, methylation, and in natural biological aging. The expression variability of a gene is an important functional characteristic of the gene itself and the classification of a gene as one with Hyper-Variability or Hypo-Variability in a human population or in a specific tissue should be useful in the identification of important genes that functionally regulate development or disease.