Examining potential confounding factors in gene expression analysis of human saliva and identifying potential housekeeping genes

Ostheim, P. and Alemu, S. W. and Tichy, A. and Sirak, I and Davidkova, M. and Stastna, M. Markova and Kultova, G. and Schuele, S. and Paunesku, T. and Woloschak, G. and Ghandhi, S. A. and Amundson, S. A. and Haimerl, M. and Stroszczynski, C. and Port, M. and Abend, M. (2022) Examining potential confounding factors in gene expression analysis of human saliva and identifying potential housekeeping genes. SCIENTIFIC REPORTS, 12 (1): 2312. ISSN 2045-2322,

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Abstract

Isolation of RNA from whole saliva, a non-invasive and easily accessible biofluid that is an attractive alternative to blood for high-throughput biodosimetry of radiological/nuclear victims might be of clinical significance for prediction and diagnosis of disease. In a previous analysis of 12 human samples we identified two challenges to measuring gene expression from total RNA: (1) the fraction of human RNA in whole saliva was low and (2) the bacterial contamination was overwhelming. To overcome these challenges, we performed selective cDNA synthesis for human RNA species only by employing poly(A)+-tail primers followed by qRT-PCR. In the current study, this approach was independently validated on 91 samples from 61 healthy donors. Additionally, we used the ratio of human to bacterial RNA to adjust the input RNA to include equal amounts of human RNA across all samples before cDNA synthesis, which then ensured comparable analysis using the same base human input material. Furthermore, we examined relative levels of ten known housekeeping genes, and assessed inter- and intra-individual differences in 61 salivary RNA isolates, while considering effects of demographical factors (e.g. sex, age), epidemiological factors comprising social habits (e.g. alcohol, cigarette consumption), oral hygiene (e.g. flossing, mouthwash), previous radiological diagnostic procedures (e.g. number of CT-scans) and saliva collection time (circadian periodic). Total human RNA amounts appeared significantly associated with age only (P <= 0.02). None of the chosen housekeeping genes showed significant circadian periodicity and either did not associate or were weakly associated with the 24 confounders examined, with one exception, 60% of genes were altered by mouthwash. ATP6, ACTB and B2M represented genes with the highest mean baseline expression (Ct-values <= 30) and were detected in all samples. Combining these housekeeping genes for normalization purposes did not decrease inter-individual variance, but increased the robustness. In summary, our work addresses critical confounders and provides important information for the successful examination of gene expression in human whole saliva.

Item Type: Article
Uncontrolled Keywords: RNA EXPRESSION; MICRORNA; DIAGNOSTICS; VALIDATION; BIOMARKERS; SIGNATURES;
Subjects: 600 Technology > 610 Medical sciences Medicine
Divisions: Medicine > Zentrum für Neuroradiologie
Depositing User: Dr. Gernot Deinzer
Date Deposited: 01 Feb 2024 13:31
Last Modified: 01 Feb 2024 13:31
URI: https://pred.uni-regensburg.de/id/eprint/58404

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