Dear All

Many thanks to all who responded and apologies if I did not get back to
everyone (some mails bounced), but here is a summary of the soundbites
I received from the community.

Briefly, at least one very reputable lab had replaced EtOH with RNA later
or similar non-branded product and the genetic material was/is fine for
subsequent analysis. There were many other queries and suggestions, of
which drying was a popular choice, especially for tissues such as fish
fin clips. I think that the comments provide really interesting reading
and thanks to everyone who responded. Certainly food for thought for
future strategies. Please see below.

Cheers and best

Si Creer

��From my experience the RNAlater solutions are fantastic for both RNA
and DNA preservation at RT and lower temperatures. Tissue tend to become
"rubbery" or "hard" in ethanol. My yields and quality of DNA was also much
higher compared to ethanol storage. Dry storage also worked acceptably.��

��What kinds of tissues are you trying to preserve and what are your
downstream plans for them? DNA-based work only? Beware that because of
its EDTA content and low pH, RNAlater will dissolve some mineralized
tissues and may form crystals around small, soft-bodied specimens (I
work on marine worms) or small tissue samples.��

Invertebrate Systematics, 2013, 27, 81�V86
http://dx.doi.org/10.1071/IS12067
DNA preservation: a test of commonly used preservatives for insects
Corrie S. Moreau A,D, Brian D. Wray A, Jesse E. Czekanski-Moir A,C and
Benjamin E. R. Rubin A,B

��Our preferred method of preserving the samples and DNA is air drying.
Briefly, we take a small fin clip (this can be done non-lethally) and
place between a small piece of filter paper to absorb the moisture.
The samples are then put into a desiccator (or warm dry area) for 3-5
days or until completely dry.  We have found that the key to preserving
high quality DNA is to begin the drying process immediately after the
tissue is removed from the fish.  Once fully dry, the samples can be
stored for years at room temperature.  As a bonus, this is a highly
space-efficient method, and we can store a large number of samples in
a small area, no reagents required.��

��We also handle some ethanol-preserved tissue.  When possible,
we transfer ethanol samples to a dried state for long-term storage.
This process involves blotting as much excess ethanol as possible with
a lab wipe or blotter paper, overnight evaporation in a fume hood,
and then ~3 days in a desiccator.��

��We have recently extracted DNA from samples that have been stored
at room temp on our sample shelf for about 10 years, and got good
microsatellite and SNP genotype data from them.  In my experience,
the majority of the DNA degradation takes place in the first few hours
following: 1) removal of the fin clip from the fish, 2) thawing of frozen
samples, or 3) death of the animal, as with carcass samples from stream
surveys.   Once the tissue has dried, enzymatic activity ceases, so the
quicker you can get the sample dry, the better.  Most of the data-poor
samples that I deal with are from salmon carcasses, and there seems to
be a strong negative correlation between data quality and amount of time
the carcass has been decomposing on the stream bank!��

��I should mention that each tissue sample gets its own envelope, on
which all the relevant sample info is written (and later entered into an
electronic database).  We use small coin envelopes that are about 9 x
5.5 cm.  I buy "#1 coin brown" envelopes from envelopes.com in the US,
but I'm sure there is a similar retailer in the UK.  The blotter paper
is Whatman 1 filter/blotter paper 46 x 57 cm, which we cut into ~2.5cm
squares.��

��exchanging RNA later for ethanol is fine for fin clips��

Simon Creer
Senior Lecturer
Molecular Ecology and Fisheries Genetics Laboratory
School of Biological Sciences
Environment Centre Wales
Bangor University
Gwynedd
LL57 2UW
Tel: +44(0)1248 382302
Fax: +44(0)1248 382569
web: http://mefgl.bangor.ac.uk/si.php
Skype: spideycreer
Twitter: @spideycreer

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