LC-MS for Quantifying an Epigenetic Motif

Tamar Shahal, Chemistry, Tel Aviv University, Tel Aviv, Israel

The sequence of the four DNA bases, determines the genetic code of living organisms. Recent publications have revealed dynamic chemical modifications on the DNA base, cytosine. These epigenetic modifications have a crucial role in regulation of gene expression. Specifically, 5-hydroxymethylcytosine (5-hmC) was found to be subjected to changes during tumorigenesis and neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and Huntington’s disease. This indicates the potential of 5-hmC as a biomarker for early disease diagnostics. The levels of 5-hmC in human tissues is extremely low (0.002-0.2% of total nucleic bases), hence extremely sensitive techniques are required for 5-hmC quantification. We are developing a liquid chromatography- mass spectroscopy (LC-MS) protocol for global assessment of 5-hmC levels in different tissues. Our protocol includes a chemical modification of the 5-hmC moiety which may decrease the method's limit of detection and enhance its sensitivity and accuracy.