Furthermore, cryopreservation of 2-cell embryos using this vitrification protocol can now be applied to maintaining valuable rat strains derived from the F344 inbred strain as genetic resources.
Rat strains were derived from multiple founder colonies and, moreover, rat strains derived from the same outbred founder colony were derived at different geographical locations where subsets of the founder colonies were distributed and then maintained.
However, since many of the current rat strains were derived from common ancestral stocks and simply inbred to increase genetic uniformity, inbred strains clearly share alleles [ 12].
The Lyon inbred rat strains were derived in the early 1970s from a single outbred Sprague Dawley (SD) colony for different blood pressure levels: hypertension (Lyon Hypertensive; LH/Mav), normotension (Lyon Normotensive; LN/Mav) and hypotension (Lyon Low-pressure; LL/Mav) [ 3].
Contrary to classical mouse inbred strains, where multiple subspecies contribute to the genetic make-up [ 13, 34] and recent mouse strains, derived from different Mus species [ 35], laboratory rat strains are most likely descending from a single rat species, Rattus norvegicus [ 10].
Each rat strain was derived either from a single pair of rats or a relatively small number of pairs and therefore underwent severe bottleneck effects between 100 and 200 generations ago.
Published: July 25 , 2013In the past 100 years, more than 500 inbred rat strains have been derived for a range of physiological and pathophysiological phenotypes (Aitman et al., 2008; Lindsey, 1979) but have been predominantly used to study cardiovascular and metabolic phenotypes, which are complex traits governed by the interaction between multiple genetic factors and the environment.
The effect of cross-fostering was greater in SD possibly because SD rats differ from the two Wistar-Kyoto derived rat strains that are genetically more closely related to each other than to the SD rat strain.
The Milan hypertensive rat strain (MHS) was derived from an outbred Wistar colony along with the normotensive MNS control strain.
Spinal cord cell suspensions from either E15.5 Wistar or Sprague Dawley outbred rat strains were plated on the neurosphere derived astrocytes.
The evolutionary history of laboratory rat strains is complex, as they were derived by multiple rounds of interbreeding and inbreeding in different locations at different points in time (Jong, 1984; Saar et al., 2008).
