Jax Labs eBook - 19


The new sequencing data from
Eve C57BL/6J (a much more realistic
representation of current B6J mice
from The Jackson Laboratory) will be
incorporated in the upcoming release of
the mouse Genome Reference sequence
"GRCm39" planned for the end of 2019/
early 2020. This will be an invaluable tool
for researchers and mutant/transgenic
cores as they design and validate
new models in the C57BL/6J genetic

Figure 2. Origin of the inbred


at F226 were recovered and there

B6J mice are living reagents subject to
genetic drift (as are all inbred strains),
an unavoidable source of accumulating
genetic variability that can have an impact
on reproducibility over time. Nearly 20
years after the first release of the mouse
reference genome, individuals from the
strain it represents (C57BL/6J) are at
least 26 inbreeding generations removed
19 | GENengnews.com

strain C57BL/6J. Inbred laboratory
mouse strains are maintained
by brother x sister mating. Filial
(F) generations from which mice
contributing to the reference
assembly clone libraries and from
which the B6Eve mouse were
derived are shown. Cryopreserved
embryo stock is represented
by blue snowflakes at F226, 3
generations from Adam and Eve
at F223. Generations subsequent
to the cryopreservation event are
F226p###, e.g., F226p230, which
means embryos cryopreserved
were an additional 4 generations
of subsequent inbreeding. Adapted
from Sarsani et al 2019.

from the breeders used to generate
the mouse reference genome GRCm38
(Figure 2). Under the highly selective
breeding paradigms employed for inbred
laboratory strains, this genetic distance
(>20 generations) is sufficient for rapid
fixation of 98.7% of variants, such that
today's C57BL/6J mice are by definition
a sub-strain of the animals from which

GRCm38 is derived.
However, since 2003, The Jackson
Laboratory manages the rate of
genetic drift by selling only B6J mice
descended from the breeder pair
so-called "Adam and Eve" by Sarsani
and collaborators (Sarsani et al.,
2019). This was accomplished by
freezing thousands of embryos of their

http://genomeref.blogspot.com/2019/05/readying-release-of-grcm39.html http://genomeref.blogspot.com/2019/05/readying-release-of-grcm39.html http://genomeref.blogspot.com/2019/05/readying-release-of-grcm39.html http://www.GENengnews.com

Jax Labs eBook

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