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Non CpG cytosine methylation - Global methylation analysis of somatic tissue (Aug/25/2005 )

Hi all,

I have had peripheral blood lymphocytes analysed for global cytosine methylation levels by two different labs, with very different reults. The first lab used an HPLC method to qunatitate total percentage of methylcytosine and the second used a digest and southern/PCR method to quantitate CpG cytosine methylation.
Am I right in thinking there must be a technical reason for the difference?
I thought levels of non-CpG methylcytosine were very low in somatic tissues?



you are correct in thinking so, HPLC quantitation measures total methyl-cytosine as the DNA is degraded to single nucleotides, the second technique involves a restriction enzyme which would tend to bias results to the recognition site of the enzyme and hence give rise to a discrepancy in results between the two techniques.