Genomic Targets in Saliva

Abstract

Saliva, the most accessible and noninvasive biofluid of our body, harbors a wide spectrum of biological analytes informative for clinical diagnostic applications. While proteomic constituents are a logical first choice as salivary diagnostic analytes, genomic targets have emerged as highly informative and discriminatory. This awareness, coupled with the ability to harness genomic information by high-throughput technology platforms such as genome-wide microarrays, ideally positions salivary genomic targets for exploring the value of saliva for detection of specific disease states and augmenting the diagnostic and discriminatory value of the saliva proteome for clinical applications. Buccal cells and saliva have been used as sources of genomic DNA for a variety of clinical and forensic applications. For discovery of disease targets in saliva, the recent realization that there is a transcriptome in saliva presented an additional target for oral diagnostics. All healthy subjects evaluated have approximately 3,000 different mRNA molecules in their saliva. Almost 200 of these salivary mRNAs are present in all subjects. Exploration of the clinical utility of the salivary transcriptome in oral cancer subjects shows that four salivary mRNAs (OAZ, SAT, IL8, and IL1b) collectively have a discriminatory power of 91% sensitivity and specificity for oral cancer detection. Data are also now in place to validate the presence of unique diagnostic panels of salivary mRNAs in subjects with Sjögren's disease.

Use of the Genome Profiling Method for the Identification of Saliva and Sweat Samples

“…This may be because the amount of total RNA is not abundantly present in sweat and semen samples or that the RNA extracted from saliva and vaginal ‰uid also contained RNA from oral and vaginal epithelium. Additionally, it was also reported that about 3000 diŠerent types of RNA exist in saliva 16) . Therefore, it is believed that large amounts of varying RNA types exist in saliva and vaginal ‰uid.…”

Forensic Genetics and Genotyping

“…Tumor-specific cell-free DNA has also been found in the circulation in many kinds of tumors. The presence of placental and tumor-specific cell-free RNA in plasma was also found (15).…”

“…In 2005, Juusola and Ballantyne demonstrated the distinction of stains originating from different body fluids such as blood, semen, saliva and vaginal secretions (59). But the main part of the RNA preserved in salivary stains is cellular (15).…”

“…Analysis of extracellular mRNA profiling in forensic science has also been investigated (56). In 2003, using standard RT-PCR and gel electrophoresis, Juusola and Ballantyne reported that mRNAs specific for saliva and semen can be detected in stains as old as 10 weeks (15,57). The mRNAs have been used for identification of human body fluids or tissues, which is very useful for forensic investigations to identify the origin of biological samples (3,58).…”

“…proteases from food particles, bacterial cells) (14) than in blood (e.g. heme, hemoglobin, lactoferin, immunoglobin G) (15,16,17). Saliva transports exfoliated epithelial cells from buccal mucosa which contains DNA and the mean number of epithelial cells per 1 mL of saliva is about 4.3 × 10 5 , which makes it a suitable source of genomic DNA (8,11,18).…”