title: Generating Chimeric Mice by Using Embryos from Nonsuperovulated BALB/c Mice Compared with Superovulated BALB/c and Albino C57BL/6 Mice.
abstract: The reliable generation of high-percentage chimeras from gene-targeted C57BL/6 embryonic stem cells has proven challenging, despite optimization of cell culture and microinjection techniques. To improve the efficiency of this procedure, we compared the generation of chimeras by using 3 different inbred, albino host, embryo-generating protocols: BALB/cAnNTac (BALB/c) donor mice superovulated at 4 wk of age, 12-wk-old BALB/c donor mice without superovulation, and C57BL/6NTac-Tyr(tm1Arte) (albino B6) mice superovulated at 4 wk of age. Key parameters measured included the average number of injectable embryos per donor, the percentage of live pups born from the total number of embryos transferred to recipients, and the number of chimeric pups with high embryonic-stem-cell contribution by coat color. Although albino B6 donors produced significantly more injectable embryos than did BALB/c donors, 12-wk-old BALB/c donor produced high-percentage (at least 70%) chimeras more than 2.5 times as often as did albino B6 mice and 20 times more efficiently than did 4-wk-old BALB/c donors. These findings clearly suggest that 12-wk-old BALB/c mice be used as blastocyst donors to reduce the number of mice used to generate each chimera, reduce the production of low-percentage chimeras, and maximize the generation of high-percentage chimeras from C57BL/6 embryonic stem cells.
authors.affiliation: Division of Laboratory Animal Medicine, Tufts University, Boston, Massachusetts, USA. mesmail@gmail.com.
authors.forename: Michael Y
authors.initials: MY
authors.lastname: Esmail
authors.affiliation: Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
authors.forename: Peimin
authors.initials: P
authors.lastname: Qi
authors.affiliation: Koch Institute of Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
authors.forename: Aurora Burds
authors.initials: AB
authors.lastname: Connor
authors.affiliation: Division of Comparative Medicine and Koch Institute of Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
authors.forename: James G
authors.initials: JG
authors.lastname: Fox
authors.affiliation: Division of Comparative Medicine and Koch Institute of Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
authors.forename: Alexis
authors.initials: A
authors.lastname: García
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology; D002678:Chimera / Q000502:physiology*; D004624:Embryo Transfer / Q000379:methods*; D053595:Embryonic Stem Cells / Q000637:transplantation*; D005260:Female; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C / Q000502:physiology*; D008810:Mice, Inbred C57BL / Q000502:physiology*; D008845:Microinjections; D013480:Superovulation / Q000502:physiology*