cDNA library from tissue at -20degC????

Jon Nakamoto jnakamot at
Sat Feb 19 20:31:42 EST 1994

A friend of mine in a lab without very much mol bio experience has been
assigned the unenviable task of making and screening a cDNA library
from rat vestibular nuclei. I'm a bit concerned that they're using rat
heads which have been stored 4 months or more at -20degC. This bothers
me a bit, because I wonder how stable the mRNA can really be under
these conditions. I told them that they should isolate and run a bit of
total RNA on a gel to check it's condition (but I still worry that,
even if it looks relatively undegraded, it may not be a good source for
a library).

Any experiences with tissues stored at this temp? Should I tell them
not to waste their time (i.e., get fresh rat heads?). Or am I being too
picky? Had the samples been stored at -70degC instead, would they be
more acceptable (and for how long a storage period would you trust them
as a source to make a cDNA library?). 

Oh, and if anybody knows of an existing rat vestibular nuclei cDNA
library, let me know so I can save my friend from unneeded work.

Thanks all,

Jon Nakamoto, MD
jnakamot at
UCLA Medical Center

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