The kick-in system: a novel rapid knock-in strategy

PLoS One. 2014 Feb 19;9(2):e88549. doi: 10.1371/journal.pone.0088549. eCollection 2014.

Abstract

Knock-in mouse models have contributed tremendously to our understanding of human disorders. However, generation of knock-in animals requires a significant investment of time and effort. We addressed this problem by developing a novel knock-in system that circumvents several traditional challenges by establishing stem cells with acceptor elements enveloping a particular genomic target. Once established, these acceptor embryonic stem (ES) cells are efficient at directionally incorporating mutated target DNA using modified Cre/lox technology. This is advantageous, because knock-ins are not restricted to one a priori selected variation. Rather, it is possible to generate several mutant animal lines harboring desired alterations in the targeted area. Acceptor ES cell generation is the rate-limiting step, lasting approximately 2 months. Subsequent manipulations toward animal production require an additional 8 weeks, but this delimits the full period from conception of the genetic alteration to its animal incorporation. We call this system a "kick-in" to emphasize its unique characteristics of speed and convenience. To demonstrate the functionality of the kick-in methodology, we generated two mouse lines with separate mutant versions of the voltage-dependent potassium channel Kv7.2 (Kcnq2): p.Tyr284Cys (Y284C) and p.Ala306Thr (A306T); both variations have been associated with benign familial neonatal epilepsy. Adult mice homozygous for Y284C, heretofore unexamined in animals, presented with spontaneous seizures, whereas A306T homozygotes died early. Heterozygous mice of both lines showed increased sensitivity to pentylenetetrazole, possibly due to a reduction in M-current in CA1 hippocampal pyramidal neurons. Our observations for the A306T animals match those obtained with traditional knock-in technology, demonstrating that the kick-in system can readily generate mice bearing various mutations, making it a suitable feeder technology toward streamlined phenotyping.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Behavior, Animal
  • Embryonic Stem Cells / metabolism
  • Epilepsy, Benign Neonatal / chemically induced
  • Epilepsy, Benign Neonatal / genetics
  • Epilepsy, Benign Neonatal / metabolism
  • Female
  • Gene Expression Regulation
  • Gene Knock-In Techniques / methods*
  • Humans
  • KCNQ2 Potassium Channel / genetics*
  • Male
  • Mice
  • Mutation
  • Pentylenetetrazole / adverse effects
  • Pregnancy
  • Proto-Oncogene Proteins c-fos / metabolism
  • Time Factors

Substances

  • KCNQ2 Potassium Channel
  • Proto-Oncogene Proteins c-fos
  • Pentylenetetrazole

Grants and funding

This work was supported in part by Grants for Scientific Research (A) (24249060 to SH), for Challenging Exploratory Research (25670481 to SH), for Bilateral Joint Research Projects (SH) from the Japan Society for the Promotion of Science (JSPS); Grants for Scientific Research on Innovative Areas (221S0002 to SH and 25129708 to SH) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT); the MEXT-supported Program for the Strategic Research Foundation at Private Universities 2013–2017 (SH); Grants-in-aid for Research on Measures for Intractable Diseases (No. H23-Nanji-Ippan-78 to SH) from the Ministry of Health, Labour and Welfare; Intramural Research Grant (21B-5 and 24-7) for Neurological and Psychiatric Disorders of NCNP (SH); the Joint Usage/Research Program of Medical Research Institute, Tokyo Medical and Dental University (SH); Grants from the Mitsubishi Foundation (SH), Takeda Scientific Foundation (SH) and the Japan Epilepsy Research Foundation (to TU); Research grants for the Central Research Institute for the Molecular Pathomechanisms of Epilepsy of Fukuoka University (SH) and Recommended Projects of Fukuoka University (117016 to SH). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.