Editing Laboratory mouse (section)

== Appearance and behaviour ==
Laboratory mice have retained many of the physical and behavioural characteristics of house mice; however, due to many generations of artificial selection, some of these characteristics now vary markedly. Due to the large number of strains of laboratory mice, it is impractical to comprehensively describe the appearance and behaviour of all of them; however, they are described below for two of the most commonly used strains.

===C57BL/6===
[[File:Black 6 mouse eating.jpg|thumb|A female C57BL/6 laboratory mouse]]
{{main|C57BL/6}} 
C57BL/6 mice have a dark brown, nearly black coat.  They are more sensitive to noise and odours and are more likely to bite than the more docile laboratory strains such as [[BALB/c]].<ref>{{cite web|url=http://www.cellmigration.org/resource/komouse/protocols/mouse_management_feb06.pdf|title=Aurora's Guide to Mo use Colony Management|vauthors=Connor AB|date=2006|work=Cell Migration Gateway|publisher=CMC Activity Center|access-date=19 December 2013|archive-date=23 September 2015|archive-url=https://web.archive.org/web/20150923201637/http://www.cellmigration.org/resource/komouse/protocols/mouse_management_feb06.pdf|url-status=dead}}</ref>

Group-housed C57BL/6 mice (and other strains) display barbering behaviour, which used to be seen as a sign of dominance. However, it is now known that this is more of a stereotypical behaviour triggered by stress, comparable to [[trichotillomania]] in humans or feather plucking in parrots.<ref>{{cite journal | vauthors = Garner JP, Weisker SM, Dufour B, Mench JA | title = Barbering (fur and whisker trimming) by laboratory mice as a model of human trichotillomania and obsessive-compulsive spectrum disorders | journal = Comparative Medicine | volume = 54 | issue = 2 | pages = 216–24 | date = April 2004 | pmid = 15134369 | url = http://www.dietvet-holistic.hu/download/ChR_2008/garner.cm.barberingepidemiology.pdf | url-status = dead | archive-url = https://web.archive.org/web/20131203003543/http://www.dietvet-holistic.hu/download/ChR_2008/garner.cm.barberingepidemiology.pdf | archive-date = 2013-12-03 }}</ref> Mice that have been barbered extensively can have large bald patches on their bodies, commonly around the head, snout, and shoulders, although barbering may appear anywhere on the body. Also self-barbering can occur. Both hair and [[whiskers|vibrissae]] may be removed. Barbering is more frequently seen in female mice; male mice are more likely to display dominance through fighting.<ref>{{cite journal | vauthors = Sarna JR, Dyck RH, Whishaw IQ | title = The Dalila effect: C57BL6 mice barber whiskers by plucking | journal = Behavioural Brain Research | volume = 108 | issue = 1 | pages = 39–45 | date = February 2000 | pmid = 10680755 | doi = 10.1016/S0166-4328(99)00137-0 | s2cid = 18334770 | citeseerx = 10.1.1.519.7265 }}</ref>

C57BL/6 has several unusual characteristics which make it useful for some research studies but inappropriate for others: It is unusually sensitive to pain and to cold, and [[analgesic]] medications are less effective in this strain.<ref>{{cite journal | vauthors = Mogil JS, Wilson SG, Bon K, Lee SE, Chung K, Raber P, Pieper JO, Hain HS, Belknap JK, Hubert L, Elmer GI, Chung JM, Devor M | display-authors = 6 | title = Heritability of nociception I: responses of 11 inbred mouse strains on 12 measures of nociception | journal = Pain | volume = 80 | issue = 1–2 | pages = 67–82 | date = March 1999 | pmid = 10204719 | doi = 10.1016/s0304-3959(98)00197-3 | s2cid = 17604906 }}</ref> Unlike most laboratory mouse strains, the C57BL/6 drinks [[alcoholic beverage]]s voluntarily. It is more susceptible than average to [[morphine addiction]], [[atherosclerosis]], and age-related [[hearing loss]].<ref name="Trouble" /> When compared directly to BALB/c mice, C57BL/6 mice also express both a robust response to social rewards<ref>{{cite journal | vauthors = Panksepp JB, Lahvis GP | title = Social reward among juvenile mice | journal = Genes, Brain and Behavior | volume = 6 | issue = 7 | pages = 661–71 | date = October 2007 | pmid = 17212648 | pmc = 2040181 | doi = 10.1111/j.1601-183X.2006.00295.x | url = }}</ref><ref>{{cite journal | vauthors = Panksepp JB, Jochman KA, Kim JU, Koy JJ, Wilson ED, Chen Q, Wilson CR, Lahvis GP | display-authors = 6 | title = Affiliative behavior, ultrasonic communication and social reward are influenced by genetic variation in adolescent mice | journal = PLOS ONE | volume = 2 | issue = 4 | pages = e351 | date = April 2007 | pmid = 17406675 | pmc = 1831495 | doi = 10.1371/journal.pone.0000351 | bibcode = 2007PLoSO...2..351P | doi-access = free }}</ref> and empathy.<ref>{{cite journal | vauthors = Chen Q, Panksepp JB, Lahvis GP | title = Empathy is moderated by genetic background in mice | journal = PLOS ONE | volume = 4 | issue = 2 | pages = e4387 | date = 2009-02-11 | pmid = 19209221 | pmc = 2633046 | doi = 10.1371/journal.pone.0004387 | bibcode = 2009PLoSO...4.4387C | doi-access = free }}</ref>

===BALB/c===
{{main|BALB/c}}
[[Image:Lightmatter lab mice.jpg|right|thumb|BALB/c laboratory mice]]
BALB/c is an [[albino]] laboratory-bred strain from which a number of common substrains are derived. With over 200 generations bred since 1920, BALB/c mice are distributed globally and are among the most widely used inbred strains used in [[animal experimentation]].<ref name="Festing">{{Cite web| title=BALB/c | work=Inbred Strains of Mice | publisher=Jackson Laboratory | url=http://www.informatics.jax.org/external/festing/mouse/docs/BALB.shtml | access-date=2007-04-16 }}</ref>

BALB/c are noted for displaying high levels of anxiety and for being relatively resistant to diet-induced [[atherosclerosis]], making them a useful model for cardiovascular research.<ref>{{Cite web|title=BALB/cByJ |work=Jax Mice Data Sheet |publisher=Jackson Laboratory |url=http://jaxmice.jax.org/strain/001026_2.html |access-date=2007-04-16 |url-status=dead |archive-url=https://web.archive.org/web/20061116054205/http://jaxmice.jax.org/strain/001026_2.html |archive-date=November 16, 2006 }}</ref><ref>{{Cite web| title=BALB/cJ | work=Jax Mice Data Sheet | publisher=Jackson Laboratory | url=http://jaxmice.jax.org/strain/000651.html | access-date=2007-04-16 | archive-url= https://web.archive.org/web/20070411205957/http://jaxmice.jax.org/strain/000651.html| archive-date= 11 April 2007}}</ref>

Male BALB/c mice are aggressive and will fight other males if housed together. However, the BALB/Lac substrain is much more docile.<ref name="aggressive">{{cite journal | vauthors = Southwick CH, Clark LH | year = 1966 | title = Aggressive behaviour and exploratory activity in fourteen mouse strains | journal = Am. Zool. | volume = 6 | page = 559 }}</ref>  Most BALB/c mice substrains have a long reproductive life-span.<ref name="Festing"/>

There are noted differences between different BALB/c substrains, though these are thought to be due to [[mutation]] rather than genetic contamination.<ref name="strains">{{cite book | vauthors = Hilgers J, van Nie R, Iványi D, Hilkens J, Michalides R, de Moes J, Poort-Keesom R, Kroezen V, von Deimling O, Kominami R | chapter = Genetic Differences in BALB/C Sublines | series = Current Topics in Microbiology and Immunology | display-authors = 6 | title = The BALB/C Mouse | volume = 122 | pages = 19–30 | year = 1985 | pmid = 2994956 | doi = 10.1007/978-3-642-70740-7_3 | isbn = 978-3-642-70742-1 }}</ref> The BALB/cWt is unusual in that 3% of progeny display true [[hermaphroditism]].<ref name="cWt">{{cite journal | vauthors = Eicher EM, Beamer WG, Washburn LL, Whitten WK | title = A cytogenetic investigation of inherited true hermaphroditism in BALB/cWt mice | journal = Cytogenetics and Cell Genetics | volume = 28 | issue = 1–2 | pages = 104–15 | year = 1980 | pmid = 7470243 | doi = 10.1159/000131518 }}</ref>

===Tg2576===
A useful model for [[Alzheimer's disease]] (AD) in the lab is the Tg2576 strain of mice. The K670M and N671L double [[mutations]] seen in the human 695 splice-variant of the [[amyloid precursor protein]] (APP) are expressed by this strain. A [[hamster]] [[prion protein]] [[gene promoter]], predominantly in neurons, drives the expression. When compared to non-transgenic littermates, Tg2576 mice show a five-fold rise in Aβ40 and a 10- to 15-fold increase in Aβ42/43.<ref>{{cite web | url=https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/tg2576-mouse#:~:text=Tg2576%20mice%20exhibit%20many%20behavioral,70%2C%2072%E2%80%9375) | title=Tg2576 Mouse - an overview &#124; ScienceDirect Topics }}</ref><ref>{{cite journal | doi=10.1007/s11357-021-00401-6 | title=Early manifestation of gait alterations in the Tg2576 mouse model of Alzheimer's disease | date=2021 | last1=Nyul-Toth | first1=Adam | last2=Delfavero | first2=Jordan | last3=Mukli | first3=Peter | last4=Tarantini | first4=Amber | last5=Ungvari | first5=Anna | last6=Yabluchanskiy | first6=Andriy | last7=Csiszar | first7=Anna | last8=Ungvari | first8=Zoltan | last9=Tarantini | first9=Stefano | journal=Geroscience | volume=43 | issue=4 | pages=1947–1957 | pmid=34160781 | pmc=8492885 }}</ref><ref>{{cite journal | url=https://www.sciencedirect.com/science/article/pii/S0197458022002536 | doi=10.1016/j.neurobiolaging.2022.11.017 | title=Neuronal hyperexcitability in the Tg2576 mouse model of Alzheimer's disease – the influence of sleep and noradrenergic transmission | date=2023 | last1=b． Szabo | first1=Anna | last2=Cattaud | first2=Vanessa | last3=Bezzina | first3=Charlotte | last4=Dard | first4=Robin F. | last5=Sayegh | first5=Fares | last6=Gauzin | first6=Sebastien | last7=Lejards | first7=Camille | last8=Valton | first8=Luc | last9=Rampon | first9=Claire | last10=Verret | first10=Laure | last11=Dahan | first11=Lionel | journal=Neurobiology of Aging | volume=123 | pages=35–48 | pmid=36634385 }}</ref> These mice develop senile plaques linked to cellular inflammatory responses because their brains have approximately five times as much transgenic mutant human APP than indigenous mouse APP. The mice exhibit main characteristics of Alzheimer's disease (AD), such as increased generation of [[amyloid fibrils]] with aging, plaque formation, and impaired [[hippocampus]] learning and memory. Tg2576 mice are a good model for early-stage AD because they show amyloidogenesis and working memory impairments  linked to age but do not show neuronal degeneration.<ref name="Transgenic Mouse Models of Alzheime">{{cite journal | doi=10.3390/ijms23105404 | doi-access=free | title=Transgenic Mouse Models of Alzheimer's Disease: An Integrative Analysis | date=2022 | last1=Sanchez-Varo | first1=Raquel | last2=Mejias-Ortega | first2=Marina | last3=Fernandez-Valenzuela | first3=Juan Jose | last4=Nuñez-Diaz | first4=Cristina | last5=Caceres-Palomo | first5=Laura | last6=Vegas-Gomez | first6=Laura | last7=Sanchez-Mejias | first7=Elisabeth | last8=Trujillo-Estrada | first8=Laura | last9=Garcia-Leon | first9=Juan Antonio | last10=Moreno-Gonzalez | first10=Ines | last11=Vizuete | first11=Marisa | last12=Vitorica | first12=Javier | last13=Baglietto-Vargas | first13=David | last14=Gutierrez | first14=Antonia | journal=International Journal of Molecular Sciences | volume=23 | issue=10 | page=5404 | pmid=35628216 | pmc=9142061 | hdl=10261/306908 | hdl-access=free }}</ref> The absence of cell death suggests that changes in typical cellular signaling cascades involved in learning and synaptic plasticity are probably linked to the memory phenotype. Associative learning impairments are exacerbated when Tg2576 mice are crossed with PS1 transgenic animals that possess the A246E FAD mutation. This crosses promotes the build-up of amyloid and plaque development in the CNS.<ref>{{cite web | url=https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/tg2576-mouse#:~:text=Tg2576%20mice%20exhibit%20many%20behavioral,70%2C%2072%E2%80%9375) | title=Tg2576 Mouse - an overview &#124; ScienceDirect Topics }}</ref> This lends credence to the theory that AD [[pathogenesis]] is influenced by the interplay between APP and PS-1 gene products. Although Tg2576 mice do not perfectly replicate late-stage AD with cell death, they do offer a platform for researching the physiology and biochemistry of the illness. With the help of transgenic mouse models, researchers can make progress in AD research by understanding the intricate relationships between gene products that are involved in the production of Aβ peptide.e physiology and biochemistry of the illness.<ref name="Transgenic Mouse Models of Alzheime"/><ref>{{cite web | url=https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/tg2576-mouse#:~:text=Tg2576%20mice%20exhibit%20many%20behavioral,70%2C%2072%E2%80%9375) | title=Tg2576 Mouse - an overview &#124; ScienceDirect Topics }}</ref>