Different regulation of adult hippocampal neurogenesis in Western house mice (Mus musculus domesticus) and C57BL/6 mice

Abstract

Adult hippocampal neurogenesis (AHN) of laboratory rodents is enhanced by physical exercise in a running wheel. However, little is known about modulation of AHN in wild-living rodent species. The finding that AHN cannot be modulated by voluntary exercise in wild wood mice suggests that AHN may be regulated differently under natural conditions than in laboratory adapted animals. In order to minimize genetic influences, we aimed to investigate the genetically closest wild-living relatives of laboratory mice. Here, C57BL/6 mice and F1 offspring of wild house mice (Mus musculus domesticus) were tested in two different running paradigms: voluntary running and running-for-food - a condition in which mice had to run for their daily allowance of food. In house mice, we found a non-significant trend towards increased numbers of proliferating cells and doublecortin-positive immature neurons in both voluntary runners and runners-for-food. Voluntary running in C57BL/6 mice resulted in a 30% increase in cell proliferation and a pronounced 70% increase in doublecortin-positive cells. C57BL/6 runners-for-food ran as much as voluntary runners, but they showed no enhancement of cell proliferation, a small increase in the number of doublecortin-positive cells and more pyknotic cells compared to controls. Taken together, these findings suggest that motivational aspects of running are critical determinants of the increased cell proliferation in C57BL/6 mice. In contrast, running has smaller and context-independent effects in house mice. The findings imply a difference in the regulation of AHN in C57BL/6 mice and their wild-derived conspecifics.

Rearing conditions and domestication background determine regulation of hippocampal cell proliferation and survival in adulthood – Laboratory CD1 and C57Bl/6 mice versus wild house mice

“…However, the measurements of the reference volumes of the granule cell layer and subgranular zone as well as the estimation of densities of BrdU-labelled cells indicate that wild house mice have a significantly larger granule cell layer than animals of the laboratory strains and in relation to that a rather moderate cell production rate. Moreover, these findings are in line with recent studies in wild-caught wood mice (Hauser et al, 2009) and western house mice (Klaus et al, 2012), in which different running and housing paradigms had no effect on cell proliferation, neither.…”

Habitat-specific shaping of proliferation and neuronal differentiation in adult hippocampal neurogenesis of wild rodents

“…This plasticity has led to concerns about the physiological importance of AHN, as key physiological parameters tend to be kept within a narrow range (Lazic, 2012). Compared to laboratory animals, the plasticity of AHN in wild rodents is much smaller—both for baseline levels in outbred species groups (Klaus and Amrein, 2012) and in response to experimental challenges (Hauser et al, 2009; Klaus et al, 2012; Schaefers, 2013). These observations not only mitigate the concern raised above, they also raise the possibility that the extent of AHN can be related to aspects of the physiology, ecology, or behavior that characterize a species rather than to acute events in the life of its members.…”

“…If the types and frequencies of such challenges are rather stable in a habitat, one may expect that there is little need for an extensive modulation of the extent of AHN. AHN in wild or wild-derived wood mice and house mice is indeed relatively stable (Hauser et al, 2009; Klaus et al, 2012; Schaefers, 2013). In the sympatric southern African rodents presented here, the stability in proliferation and neuronal differentiation is maintained across three murid taxonomic units.…”

“…For comparisons between warm and cold environments, we included data of the following European rodent species (all of the family Muridae; subfamily Murinae) from previous studies in our laboratory: Yellow-necked wood mouse ( Apodemus flavicollis , n = 8) and pygmy field mouse [ Apodemus microps ( uralensis ), n = 4] (Amrein et al, 2004a,b), both from the Tvier Rayon, Russia, long-tailed wood mouse ( Apodemus sylvaticus , n = 9) (Hauser et al, 2009) and F1 of wild-trapped house mouse ( Mus musculus domesticus , n = 7) (Klaus et al, 2012), both obtained from Zurich, Switzerland.…”

Linking adult olfactory neurogenesis to social behavior

“…Importantly, the levels of adult neurogenesis and its regulation differ across rodent species, particularly between wild and laboratory mice (Amrein et al, 2004; Klaus et al, 2012): while environmental enrichment and physical activity increase neurogenesis in laboratory mice, this effect is less pronounced in wild mice (Klaus et al, 2012). Thus, it is possible that the difficulty in pinning down the contribution of adult-generated neurons to behavior arises from studying mice in laboratory conditions, where they live in a restricted, stimulus-poor environment.…”