Elsevier

Brain Research

Volume 771, Issue 1, 10 October 1997, Pages 1-13
Brain Research

Research report
Assessing the effects of the 129/Sv genetic background on swimming navigation learning in transgenic mutants: a study using mice with a modified β-amyloid precursor protein gene

https://doi.org/10.1016/S0006-8993(97)00673-2Get rights and content

Abstract

The Morris water maze is frequently used to screen mutant mice generated by gene targeting. Targeted ES-cells are often derived from 129/Sv or BALB/c mice, known as poor swimming navigation learners. After mating the founders with C57BL/6 mice, the F2 or F3 hybrid generation is typically used for behavioral testing. In hybrid 129/Sv×C57BL/6 mice, a modification of the βAPP gene entails impaired swimming navigation learning. This is readily detected despite behavioral variability, because wild-type 129/Sv×C57BL/6 hybrids outperform either of the parental strains and provide a control sample with good baseline performance. However, after backcrossing to the 129/Sv(ev) strain, the mutation effects are no longer detectable, masked by the very poor performance of wild-type 129/Sv(ev) mice. We conclude that F2 and F3 generations of 129/Sv×C57BL/6 crosses provide a suitable genetic background for behavioral testing of transgenic mice, provided that the samples are large enough to compensate for genetic and epigenetic variability and provided that normal performance in the control group is verified by comparison against a large database of mice tested under identical conditions. Creating congenic lines by backcrossing to an inbred strain is unlikely to enhance the sensitivity of the Morris test. Backcrossing to 129/Sv(ev) may even reduce it.

Introduction

Gene targeting by homologous recombination in mouse embryonic stem (ES) cells has become an important tool for the analysis of genes thought to be involved in development and function of the central nervous system, in particular in learning and memory 16, 22, 35, 41. The Morris water maze [26]has been used to screen the learning capabilities of many mutants generated by gene targeting techniques. For a number of mutations it has revealed alterations of learning behavior 1, 2, 5, 7, 15, 19, 28, 30, 33, 46. In other studies, however, mutant mice failed to show significantly altered behavior in the water maze 4, 15, 25, 29. Reliable documentation and proper interpretation of the absence of negative behavioral effects may be as important as the analysis of deficits, for example for mutations with therapeutic or preventive potential. Such a case is the generation of scrapie resistant animals which lack a functional PrP gene 3, 43. Gene targeting in mice has also been used to determine whether normal expression of the amyloid precursor protein (βAPP) is essential for brain function 27, 47. This question is important, because the neuritic plaques which are a hallmark of Alzheimer's pathology are rich in amyloid β-peptide, a proteolysis product of βAPP. Thus, reduction of βAPP expression may provide ways to treat the disease [20].

The genetic background, i.e. the donor strain of the ES-cells used for the gene targeting procedure, is usually determined by technical considerations, such as availability of ES-cell lines, efficiency of breeding, and selection of transmitting animals by examination of fur color. ES-cells are often derived from inbred 129 (129/Sv, 129/J, 129/Ola) or BALB/c mice and transmitting chimeras are then mated to C57BL/6 mice [13]. Rapid results can be obtained if the mutation phenotype is investigated by comparing littermates in the F2 generation of such a cross. This type of procedure has also been employed in the recent generation and analysis of mice bearing a modification of the amyloid precursor protein (βAPP) gene which causes βAPP to be expressed at ca. 5% of wild-type levels and in a truncated form. We have found these mice to be severely impaired in learning the Morris water maze navigation task [27].

Pathology and survival rate of mice with induced mutations can change dramatically with different genetic backgrounds 9, 18, 32, 34, 36, indicating that the genetic background can profoundly affect the phenotype of a mutation. On the other hand, under baseline conditions, behavior and learning capabilities in the water maze show large differences between different inbred strains of mice 14, 17, 23, 38, 40, 42. In particular, the 129/Sv and BALB/c strains are known as poor swimming navigation learners 24, 44, while inbred C57BL/6 are fairly good learners 10, 31, 37, 38, 40. Moreover, the effect of anticholinergic treatment on water-maze learning in mice has been shown to depend on the genetic background 37, 39. However, in spite of much discussion 6, 8, 12, 13, 21, insufficient data is available documenting to which extent the genetic background can interfere with the behavioral characterization of mutants generated by gene targeting techniques. Here, we report that the effects of a modified βAPP gene on water-maze learning are masked in backcrosses to the 129/Sv(ev) strain.

Section snippets

Animals

The production of βAPP mutant mice has already been described in detail elsewhere [27]. In summary, a cassette containing a neomycin resistance gene and a transcription termination sequence was introduced into exon two of the βAPP gene of D3 ES cells, derived from 129/Sv(ev) mice (passage 13, obtained from E. Wagner). ES cells heterozygous for the interrupted βAPP gene were then injected into 3.5 day-old C57BL/6 blastocysts which were implanted into the uteri of pseudopregnant CD2 F1 mice. The

Comparison of parental strains and wild-type hybrid mice

The statistics of learning and retention effects within the experimental groups are shown in Table 1 and Table 2. The results of two-way ANOVA (genetic background by sex) and post-hoc Scheffé comparison of genetic backgrounds are summarized in Table 3 and Table 4. Group means of selected parameters are illustrated in Fig. 1. Three genetic backgrounds were compared: C57 (inbred C57BL/6), 129/Sv (inbred 129/Sv(ev) and wild-type 129-backcross), and hybrid (C57BL/6×129/Sv(ev), i.e. all wild-type

The APP mutation effect is confirmed

The results of swimming navigation testing of mutant and wild-type hybrid mice indicate that about half of the mutant mice had severely reduced escape performance and spatial orientation, while some mutant mice seemed less severely affected. Mutant mice seemed not principally unable to learn the task, but their acquisition was instable, retarded and inaccurate. Since the deficit in the affected mice prevented them from acquiring the task properly, they also showed poor scores for spatial

Acknowledgements

We thank C. Weissmann for continuous support and helpful discussions and F. Magara for critical reading of the manuscript. The study was supported by Swiss NF 31-42374.94 to D.P.W. and a Human Frontiers Science Program grant to H.P.L. We thank S. Sisodia for providing antibodies against APP.

References (47)

  • R.G.M. Morris

    Developments of a water-maze procedure for studying spatial learning in the rat

    J. Neurosci. Methods

    (1984)
  • U. Müller et al.

    Behavioral and anatomical deficits in mice homozygous for a modified β-amyloid precursor protein gene

    Cell

    (1994)
  • R. Paylor et al.

    Behavioral assessment of c-fos mutant mice

    Brain Res.

    (1994)
  • M. Upchurch et al.

    Heterosis and resistance to DFP effects on spatial learning in C57BL X DBA hybrids

    Brain Res. Bull.

    (1988)
  • M. Upchurch et al.

    DBA/2Ibg mice are incapable of cholinergically-based learning in the Morris water task

    Pharmacol. Biochem. Behav.

    (1988)
  • J.M. Wehner et al.

    Hippocampal protein kinase C activity is reduced in poor spatial learners

    Brain Res.

    (1990)
  • D.P. Wolfer et al.

    A new computer program for detailed off-line analysis of swimming navigation in the Morris water maze

    J. Neurosci. Methods

    (1992)
  • H. Zheng et al.

    β-amyloid precursor protein-deficient mice show reactive gliosis and decreased locomotor activity

    Cell

    (1995)
  • S. Brandner et al.

    Normal host prion protein necessary for scrapie-induced neurotoxicity

    Nature

    (1996)
  • H. Büeler et al.

    Normal development and behaviour of mice lacking the neuronal cell-surface PrP protein

    Nature

    (1992)
  • F. Conquet et al.

    Motor deficit and impairment of synaptic plasticity in mice lacking mGluR1

    Nature

    (1994)
  • H. Cremer et al.

    Inactivation of the N-CAM gene in mice results in size reduction of the olfactory bulb and deficits in spatial learning

    Nature

    (1994)
  • L.A. Donehower et al.

    Effects of genetic background on tumorigenesis in p53-deficient mice

    Mol. Carcinogen.

    (1995)
  • Cited by (119)

    • Comorbid sensorimotor and emotional profiles in the forced swim test immobility and predictive value of a single assay in very old female mice

      2019, Experimental Gerontology
      Citation Excerpt :

      Strain determines the baseline behaviour in the FST and the response to treatment. C57BL/6 × 129/Sv mice show good baseline performance in other tests involving swimming (Wolfer et al., 1997). With respect to age, performance in rats show increase of immobility with aging.

    • Longitudinal behavioral changes in the APP/PS1 transgenic Alzheimer's Disease model

      2013, Behavioural Brain Research
      Citation Excerpt :

      At all test ages except the initial age of 7 months, the transgenic mice swam fastest on day 1, while day 5 was typically much slower. The inverse was true of floating, a similar pattern of which has been described in mutant mice [46]. Floating and thigmotactic behavior are common water maze behaviors of mice in general [31,47]; however, the pattern exhibited here seemed to suggest that the transgenic mice were most motivated on the first test day of each month but on the subsequent four days, failed to make a strong effort to locate the platform.

    • Mouse models of Alzheimer's disease

      2012, Brain Research Bulletin
    View all citing articles on Scopus
    View full text