C57BL/6



C57BL/6, often referred to as "C57 black 6", "C57" or "black 6" (standard abbreviation: B6), is a common inbred strain of laboratory mice.

It is the most widely used "genetic background" for genetically modified mice for use as models of human disease. They are the most widely used and best-selling mouse strain, due to the availability of congenic strains, easy breeding, and robustness.

Appearance and behavior
C57BL/6 mice have a dark brown, nearly black coat, and an easily irritable temperament. They have a tendency to bite and cannot be handled like a typical pet mouse or more docile laboratory strains such as BALB/c.

They are good breeders.

Group-housed B6 mice display barbering behavior, in which the dominant mouse in a cage selectively removes hair from its subordinate cage mates. Mice that have been barbered have large bald patches on their bodies, commonly around the head, snout, and shoulders, although barbering may appear anywhere on the body. Both hair and vibrissae may be removed. Barbering is more frequently seen in female mice; male mice are more likely to display dominance through fighting.

C57BL/6 has many unusual characteristics that make it useful for some work and inappropriate for other: It is unusually sensitive to pain and to cold, and analgesic medications are less effective in it. Unlike most mouse strains, it drinks alcoholic beverages voluntarily. It is more susceptible than average to morphine addiction, atherosclerosis and age-related hearing loss. Because nearly all of the mice are used at a young age and given inadequate exercise, the standard for the vast majority of lab research has been described as "a teenaged, alcoholic couch potato with a weakened immune system".

Genetics
The C57BL/6 mouse was the second-ever mammalian species to have its entire genome published.

The dark coat makes the mouse strain convenient for creating transgenic mice: it is crossed with a light-furred 129 mouse, and the desirable crosses can be easily identified by their mixed coat colors.

Popularity
By far the most popular laboratory rodent, the C57BL/6 mouse accounts for half to five-sixths of all rodents shipped to research laboratories from American suppliers. Its overwhelming popularity is due largely to the detailed knowledge of its physiology and genetics: it has been widely used and widely studied, and therefore it is used even more.

One study has shown that about four-fifths of mice used in lab studies for pain are males. Using both sexes is believed to increase costs, and using females is believed to produce unreliable results due to natural variations in the estrous cycle for reproduction.

Origin
The inbred strain of C57BL mice was created in 1921 by C. C. Little at the Bussey Institute for Research in Applied Biology. The subline "6" was the most popular of the ten sublines of this strain.

Substrains
C57BL/A Inbr(A) ?+142. Origin. Little to A c1932. Maint. by A.

C57BL/An Little to Andervont 1932. Differs from B6 and B10 at the Ce1 locus.

C57BL/GrFa. Origin: Little to Gruneberg 1932, to Falconer 1947. Most British substrains derived from this stock, though 6 and 10 substrains have been imported more recently. This substrain seems to resemble the 6 rather than the 10 substrain.

C57BL/KaLwN. To N 1965 from Lw at F35.

C57BL/Ks

C57BL/6 Inbr (J) 150. Origin: substrains 6 and 10 were separated prior to 1937. This substrain is now probably the most widely used of all inbred strains. Substrain 6 and 10 differ at the H9, Igh2 and Lv loci. Maint. by J,N, Ola.

C57BL/10 Inbr (J) 158. Origin: see C57BL/6.

C57BL/10ScSn. Inbr (J) ? +136. Little to W.L.Russell to J.P.Scott at F26 as a separate substrain. To Snell at F35-36. Behaviour differs from C57BL/10J.

C57BL/10Cr Carries spontaneous lipopolysaccharide mutation lps which appears to resemble that found in C3H/HeJ.

C57BL/Ola Carries a spontaneous mutation, Wlds, causing a marked slowing of axonal degeneration during Wallerian degeneration.