Conserving, Distributing and Managing Genetically Modified Mouse Lines by Sperm Cryopreservation - Genetic Engineering: Recent Developments in Applications - page 70

The developmental capacity of embryos produced using cryopreserved sperm
was compared to that of cryopreserved IVF-derived embryos to illustrate the
relative efficiency of different methods available for archiving GM mouse lines.
The use of cryopreserved sperm was not associated with a reduction in the per-
centage of embryos developing to liveborn for any of the groups (Figure 3b).
However, the use of cryopreserved sperm was associated with an increase in the
production of liveborn in three groups (C57BL/6J, BALB/cByJ, BALB/cJ). Per-
haps genetic differences among strains predispose IVF produced embryos from
C57BL/6J, BALB/cByJ, BALB/cJ mice to cryopreservation damage, resulting in
lowered developmental competency. These observations demonstrate that the
developmental competence of embryos produced using cryopreserved sperm is
equal to or greater than the developmental competence of cryopreserved em-
bryos produced by IVF.
Implications of Efficient Mouse Sperm Cryopreservation and
recovery
We report here a simple, inexpensive sperm cryopreservation and recovery meth-
od that is easier to implement than other reported methods[12], [14], [15]. The
cryopreservation medium is simple to make, the freezing apparatus is easily con-
structed, sperm separation is not required, and only minor modifications to stan-
dard IVF protocols are needed. The breadth of applicability (Figure 3a, Figure 3b)
and efficiency demonstrated (Figure 3a, Figure 3b) illustrate the general utility
and robustness of the approach. Comparable rates of fertilization were observed
for most genetic backgrounds whether cryopreserved or freshly collected sperm
was used. Likewise, the developmental competence of embryos derived using
cryopreserved sperm was comparable or superior to cryopreserved, IVF-derived
embryos.
Unless it is necessary to preserve multiple mutations or the entire genome,
the efficiencies reported here make sperm cryopreservation preferable to embryo
cryopreservation in many cases, provided appropriate females will be available in
the future. Sperm cryopreservation can also be preferable to maintaining small
colonies. Often, once strains are no longer under active investigation, they are
reduced to only a few breeding pairs, placing them at risk from breeding prob-
lems, genetic drift, and genetic contamination. When needed, these colonies are
scaled up; a process that often takes months. Sperm cryopreservation offers an
economical alternative by eliminating ongoing breeding costs and reducing the
time to produce experimental cohorts, as the number of oocyte donors for IVF or
the number of females used for artificial insemination can easily be scaled up to
produce the desired number of animals.