Development of SHIRPA to characterise the phenotype of gene-targeted mice

Locomotor deficiencies and aberrant development of subtype-specific GABAergic interneurons caused by an unliganded thyroid hormone receptor alpha1

Thyroid hormone (TH) deficiency during development causes severe and permanent neuronal damage, but the primary insult at the tissue level has remained unsolved. We have defined locomotor deficiencies in mice caused by a mutant thyroid hormone receptor alpha1 (TR alpha1) with potent aporeceptor activity attributable to reduced affinity to TH. This allowed identification of distinct functions that required either maternal supply of TH during early embryonic development or sufficient innate levels of hormone during late fetal development. In both instances, continued exposure to high levels of TH after birth and throughout life was needed. The hormonal dependencies correlated with severely delayed appearance of parvalbumin-immunoreactive GABAergic interneurons and increased numbers of calretinin-immunoreactive cells in the neocortex. This resulted in reduced numbers of fast spiking interneurons and defects in cortical network activity. The identification of locomotor deficiencies caused by insufficient supply of TH during fetal/perinatal development and their correlation with subtype-specific interneurons suggest a previously unknown basis for the neuronal consequences of endemic cretinism and untreated congenital hypothyroidism, and specifies TR alpha1 as the receptor isoform mediating these effects.

Analysis of neural cell function in gene knockout mice: behavior

A powerful tool to investigative gene function is the ability to create mice with targeted gene mutations. Analysis of the resulting phenotype is sometimes difficult, however, because individual genes have more than one function, and observed effects on complex behaviors are often a result of abnormalities of any of a number of individual processes. One way to address this issue is by examining mice in a battery of behavioral tests to assess the specificity of any observed differences among genotypes. This chapter describes a test battery used to examine metabolic and behavioral phenotypes in mice with mutations in specific glycan-binding proteins and glycosyltransferases genes. Because the potential consequences of these genetic deletions are varied, a large number of assays across a variety of domains was included in the battery. The power and usefulness of this approach is in discovering areas for more detailed investigation.

Modeling the monosomy for the telomeric part of human chromosome 21 reveals haploinsufficient genes modulating the inflammatory and airway responses

Monosomy 21 is a rare human disease due to gene dosage errors disturbing a variety of physiological and morphological systems including brain, skeletal, immune and respiratory functions. Most of the human condition corresponds to partial or mosaic monosomy suggesting that Monosomy 21 may be lethal. In order to search for dosage-sensitive genes involved in the human pathology, we generated by chromosomal engineering a monosomic mouse for the Prmt2-Col6a1 interval corresponding to the most telomeric part of human chromosome 21. Haploinsufficiency of the 13 genes, located in the 0.5 Mb genetic interval and conserved in man and mouse, caused apparently no morphological defect as observed in patients. However, monosomic mice displayed an enhanced inflammatory response after local intranasal lipopolysaccharide administration with enhanced recruitment of neutrophils and secretion of cytokines such as tumor necrosis factor-alpha (TNF-alpha), IL-1beta, IL-12p70 and IFN-gamma in the lung as well increased TNF-alpha production after systemic administration. Further analysis demonstrates that monosomic macrophages were involved and that a few genes, Prmt2, Pcnt2, Mcm3ap and Lss located in the region were candidate for the inflammatory response. Altogether, these results demonstrate the existence of dosage-sensitive genes in the Prmt2-Col6a1 region that control the inflammation and the lung function. Furthermore, they point out that similar partial Monosomies 21 in human might have eluded the diagnosis due to the very specific defects observed in this murine model.

Depletion of Complexin II does not affect disease progression in a mouse model of Huntington's disease (HD); support for role for complexin II in behavioural pathology in a mouse model of HD

Huntington's disease (HD) is a progressive, inherited, neurological disorder with a complicated phenotype that is characterised by movement abnormalities, cognitive impairments and psychiatric symptoms. Although HD is a neurodegenerative disease, recent evidence indicates that neurological dysfunction, rather than frank neurodegeneration contributes to, and may even cause early symptoms in the absence of neurodegeneration. One protein that may contribute to neurological dysfunction in HD is complexin II. Complexins are presynaptic proteins that are believed to modulate neurotransmitter release. Complexin II levels are reduced in human HD striatum and cortex, and a progressive depletion of complexin II mRNA and protein has also been shown in the R6/2 mouse model of HD. Interestingly, complexin II knockout mice share behavioural deficits in reversal learning in common with R6/2 mice. Further, the two strains both show abnormalities in long-term potentiation. This evidence led us to wonder whether or not loss of complexin II underlies some of the behavioural deficits seen in R6/2 mice. To investigate this, we crossbred complexin II knockout mice with R6/2 mice to generate a double mutant mouse. The behavioural phenotype of R6/2 mice on a null complexin II background was characterised and was compared to that seen in control mice. Complete knockout of complexin II did not significantly affect the phenotype of R6/2 mice. This indicates that loss of complexin II is part of the mechanism underlying the R6/2 phenotype. Whether it is causal or compensatory remains to be determined.

Systemic administration of Congo red does not improve motor or cognitive function in R6/2 mice

Huntington's disease (HD) is a progressive neurodegenerative disorder for which there is no treatment. Prior to the onset of symptoms, abnormal protein aggregates (inclusions) are found in neurons in humans and R6/2 mice. It has been suggested that the progression of HD can be slowed or prevented by disruption of the aggregation process. In agreement with this, it has been reported that systemic treatment of R6/2 mice with Congo red caused a reduction in numbers of striatal inclusions and an improvement in motor symptoms and survival [Sanchez, I., Mahlke, C., Yuan, J., 2003. Pivotal role of oligomerization in expanded polyglutamine neurodegenerative disorders. Nature 421, 373-379]. Here we attempted to replicate this study. We extended the experiment to include measurement of the effects of Congo red on cognitive function in R6/2 mice. Congo red treatment failed to ameliorate either motor or cognitive deficits in R6/2 mice. We suggest that this is due to the inability of Congo red to cross the blood-brain barrier. Since it does not improve the behavioural deterioration that is a key feature of HD, Congo red is unlikely to be useful as a therapy for HD.

Sensory defects in Necdin deficient mice result from a loss of sensory neurons correlated within an increase of developmental programmed cell death

Background

The human NECDIN gene is involved in a neurodevelopmental disorder, Prader-Willi syndrome (PWS). Previously we reported a mouse Necdin knock-out model with similar defects to PWS patients. Despite the putative roles attributed to Necdin, mainly from in vitro studies, its in vivo function remains unclear. In this study, we investigate sensory-motor behaviour in Necdin deficient mice. We reveal cellular defects and analyse their cause.

Results

We report sensory differences in Necdin deficient mice compared to wild type animals. These differences led us to investigate sensory neuron development in Necdin deficient mouse embryos. First, we describe the expression pattern of Necdin in developing DRGs and report a reduction of one-third in specified sensory neurons in dorsal roots ganglia and show that this neuronal loss is achieved by E13.5, when DRGs sensory neurons are specified. In parallel, we observed an increase of 41% in neuronal apoptosis during the wave of naturally occurring cell death at E12.5. Since it is assumed that Necdin is a P75NTR interactor, we looked at the P75NTR-expressing cell population in Necdin knock-out embryos. Unexpectedly, Necdin loss of function has no effect on p75NTR expressing neurons suggesting no direct genetic interaction between Necdin and P75NTR in this context.

Although we exclude a role of Necdin in axonal outgrowth from spinal sensory neurons in early developmental stages; such a role could occur later in neuronal differentiation. Finally we also exclude an anti-proliferative role of Necdin in developing sensory neurons.

Conclusion

Overall, our data show clearly that, in early development of the nervous system, Necdin is an anti-apoptotic or survival factor.

Receptor protein tyrosine phosphatase gamma is a marker for pyramidal cells and sensory neurons in the nervous system and is not necessary for normal development

In order to gain insight into the biological role of receptor protein tyrosine phosphatase gamma (RPTPgamma), we have generated RPTPgamma-null mice. RPTPgamma was disrupted by insertion of the beta-galactosidase gene under the control of the RPTPgamma promoter. As the RPTPgamma-null mice did not exhibit any obvious phenotype, we made use of these mice to study RPTPgamma expression and thus shed light on potential biological functions of this phosphatase. Inspection of mouse embryos shows that RPTPgamma is expressed in a variety of tissues during embryogenesis. RPTPgamma is expressed in both embryonic and adult brains. Specifically, we detected RPTPgamma expression in cortical layers II and V and in the stratum pyramidale of the hippocampus, indicating that RPTPgamma is a marker for pyramidal neurons. Mixed primary culture of glial cells showed a lack of expression of RPTPgamma in astrocytes and a low expression of RPTPgamma in oligodendrocytes and in microglia. Interestingly, RPTPgamma expression was detected in all sensory organs, including the ear, nose, tongue, eye, and vibrissa follicles, suggesting a potential role of RPTPgamma in sensory neurons. An initial behavioral analysis showed minor changes in the RPTPgamma-null mice.

Behavioural and histopathological alterations in mice with cerebral malaria

Different features of sensorimotor function and behaviour were studied in murine cerebral malaria (CM) and malaria without cerebral involvement (non-CM) applying the primary screen of the SHIRPA protocol. Histopathological analysis of distinct brain regions was performed and the relative size of haemorrhages and plugging of blood cells to brain vasculature was analysed. Animals suffering from CM develop a wide range of behavioural and functional alterations in the progressive course of the disease with a statistically significant impairment in all functional categories assessed 36 h prior to death when compared with control animals. Early functional indicators of cerebral phenotype are impairments in reflex and sensory system and in neuropsychiatric state. Deterioration in function is paralleled by the degree of histopathological changes with a statistically significant correlation between the SHIRPA score of CM animals and the mean size of brain haemorrhage. Furthermore, image analysis yielded that the relative area of the brain lesions was significantly larger in the forebrain and brainstem compared with the other regions of interest. Our results indicate that assessment of sensory and motor tasks by the SHIRPA primary screen is appropriate for the early in vivo discrimination of cerebral involvement in experimental murine malaria. Our findings also suggest a correlation between the degree of functional impairment and the size of the brain lesions as indicated by parenchymal haemorrhage. Applying the SHIRPA protocol in the functional characterization of animals suffering from CM might prove useful in the preclinical assessment of new antimalarial and potential neuroprotective therapies.

Short photoperiods impair spatial learning and alter hippocampal dendritic morphology in adult male white-footed mice (Peromyscus leucopus)

Although seasonal changes in brain morphology and function are well established in songbirds, seasonal plasticity of brain structure and function remain less well documented in mammals. Nontropical animals display many adaptations to reduce energy use to survive winter, including cessation of reproductive activities. Because of the high energetic costs of brain tissue, we hypothesized that male white-footed mice (Peromyscus leucopus) would reduce brain size in response to short days as well as regress their reproductive systems. Because short days may decrease hippocampal volume and impair spatial learning and memory in rodents and because of the potential for seasonal plasticity in the hippocampus, we hypothesized that photoperiod alters hippocampal morphology to affect spatial learning and memory. Mice housed in either long or short days for 10 weeks were examined for performance in a water maze; brains were then removed and weighed, and hippocampal volumes were determined. We also measured dendritic morphology and spine density in the CA1, CA3, and dentate gyrus. Short days decreased brain mass and hippocampal volume compared with long days. Short days also impaired long-term spatial learning and memory relative to long days but did not affect sensory discrimination or other types of memory. Short days decreased apical (stratum lacunosum-moleculare) CA1 spine density, as well as increased basilar (stratum oriens) CA3 spine density. Results from this study suggest that photoperiod alters brain size and morphology, as well as cognitive function. Understanding the mechanisms mediating these photoperiod-induced alterations may provide insight for treatment of seasonal cognitive and affective disorders.

Behavioral seizure correlates in animal models of epilepsy: a road map for assay selection, data interpretation, and the search for causal mechanisms

A broad spectrum of learning/memory, social interaction, and affective behavioral measures serve as functional correlates for neurobiological changes in seizure-prone animals as well as in epileptic clinical populations. The utility of such measures is demonstrated by their ability to distinguish anomalous characteristics in developing organisms predisposed to seizure onset, as well as to discriminate prior seizure history in organisms with established pathology. For instance, typical findings that generalize across species suggest that seizure-experienced organisms exhibit a variety of deficits in cognitive function as well as inappropriate social neglect and aggression. Behavioral testing batteries have also proven useful in assessing neural mechanisms for seizure induction, subcortical neural circuits, and neuropeptide modulators, for example, as well as in identifying neural pathology resulting from prior seizure activity. However, the wanton application of behavioral tests can also produce false positives in the identification of seizure-related disorders unless alternative performance and motivational hypotheses are discounted effectively. Accordingly, the present review attempts to provide the reader interested in behavioral phenotyping and characterization of seizure-prone rats and mice with a roadmap for rational selection, implementation, and interpretation of data from behavior assays while highlighting potential successes and pitfalls inherent in employing functional correlates of brain activity using animal models of epilepsy.

Training and aging modulate the loss-of-balance phenotype observed in a new ENU-induced allele of Otopetrin1

BACKGROUND INFORMATION

The sensing of head movement in mammals depends upon the vestibular endorgan of the inner ear, a complex structure made up of the semicircular canals and otoliths. Due to the similarity between the human and mouse vestibular apparatus, the analysis of mutant mouse is a valuable strategy aiming to identify genes involved in the control of balance and movement.

RESULTS

In the course of a genome-wide chemical-mutagenesis programme, we isolated a recessive mutation, named ied (inner ear defect), which induced a severe loss-of-balance. A detailed phenotypic analysis of the mutant mice demonstrates that the balance impairment does not affect the motor activity and can be rescued, in part, by training, despite a complete agenesis of otoconia in the utricule and the saccule of the inner ear. Molecular characterization of the ied mutation revealed a transversion that affects the splicing of the second exon of the Otopetrin1 gene located on mouse chromosome 5. The consequence of such a mutation leads to a disruption of the transcription of the gene.

CONCLUSIONS

The identification of the ied knock-down allele strengthens the role of the Otopetrin1 in the sensing of balance. Moreover, the rescue of the ied mutant phenotype in specific behavioural tasks confirmed that other sensory inputs or neural plasticity can compensate, to some extent, for the loss-of-balance. In the future, the ied mutant mice might be helpful to study the genetic control of the compensation strategies developed by organisms to counteract balance defects.

Implementation of the modified-SHIRPA protocol for screening of dominant phenotypes in a large-scale ENU mutagenesis program

SHIRPA is a three-stage protocol for the comprehensive assessment of primarily mouse behavior. The first stage consists of high-throughput phenotyping of 33 behavioral observations and 7 metabolic or disease observations. We modified this part of the protocol by integrating new morphologic observations into the initial phenotype assay of behavior and dysmorphology. Behavioral observations assessed by this protocol, now referred to as the "modified-SHIRPA," are compatible with the original "SHIRPA" protocol. Using modified-SHIRPA, we screened dominant phenotypes of more than 10,000 G(1) progeny generated by crossing DBA/2J females with ENU-treated C57BL/6J males. To date, we have obtained 136 hereditary-confirmed mutants that exhibit behavioral and morphologic defects. Some independent mutant lines exhibited similar phenotypes, suggesting that they may represent alleles of the same gene or mutations in the same genetic pathway. They could hold great potential for the unraveling of the molecular mechanisms of certain phenotypes.

Phenotypic studies on dopamine receptor subtype and associated signal transduction mutants: insights and challenges from 10 years at the psychopharmacology-molecular biology interface

BACKGROUND

Mutants with targeted gene deletion ('knockout') or insertion (transgenic) of D1, D2, D3, D4 and D5 dopamine (DA) receptor subtypes are complemented by an increasing variety of double knockout and transgenic-'knockout' models, together with knockout of critical components of DA receptor signalling cascades such as G alpha(olf)[G gamma7], adenylyl cyclase type 5, PKA [RIIbeta] and DARPP-32. However, it is increasingly recognised that these molecular techniques have a number of inherent limitations. Furthermore, there are poorly understood methodological factors that contribute to inconsistent phenotypic findings between laboratories.

OBJECTIVE

This review seeks to document the impact of DA receptor subtype and related transduction mutants on our understanding of the behavioural roles of these entities, primarily at the level of unconditioned psychomotor behaviour.

METHODS

It includes ethologically based and orofacial movement studies in our own laboratories, since these are the only studies to systematically compare each of the D1, D2, D3, D4 and D5 receptor and DARPP-32 signal transduction 'knockouts'.

DISCUSSION

There is a particular emphasis on identifying methodological factors that might influence phenotypic effects and account for inconsistencies. The findings are offered empirically to (1) specify the extent of phenotypic diversity among individual DA receptor subtypes and transduction components and (2) indicate relationships between D1, D2, D3, D4 and D5 receptor subtype proteins, associated G alpha(i)/G alpha(s)/G alpha(olf)[G gamma7]-adenylyl cyclase type 5-PKA [RIIbeta]-DARPP-32 signalling cascades and behaviour. The findings are also offered heuristically as a base for such phenotypic comparisons at additional levels of behaviour so that a yet more complete phenotypic profile might emerge.

Profound ataxia in complexin I knockout mice masks a complex phenotype that includes exploratory and habituation deficits

Complexins are presynaptic proteins that bind to the SNARE complex where they modulate neurotransmitter release. A number of studies report changes in complexins in psychiatric (schizophrenia and depression) and neurodegenerative disorders (Huntington's disease, Wernicke's encephalopathy and Parkinson's disease). Here, we characterize the behavioural phenotype of Cplx1 knockout (Cplx1-/-) mice. Cplx1-/- mice develop a strong ataxia in the absence of cerebellar degeneration. Although originally reported to die within 2-4 months after birth, when reared using an enhanced feeding regime, these mice survive normally (i.e. >2 years). Cplx1-/- mice show pronounced deficits in motor coordination and locomotion including abnormal gait, inability to run or swim, impaired rotarod performance, reduced neuromuscular strength, dystonia and resting tremor. Although the abnormal motor phenotype dominates their overt symptoms, Cplx1-/- mice also show other behavioural deficits, particularly in complex behaviours. They have deficits in grooming and rearing behaviour and show reduced exploration in several different paradigms. They also show deficits in tasks reflecting emotional reactivity. They fail to habituate to confinement and show a 'panic' response when exposed to water. The abnormalities seen in the behaviour of Cplx1-/- mice reflect those predicted from the distribution of complexin I in the brain. Our data show that complexin I is essential not only for normal motor function in mice, but also for normal performance of other complex behaviours. These results support the idea that altered expression of complexins in disease states may contribute to the symptomatology of disorders in which they are dysregulated.

Generation and characterization of Rgs4 mutant mice

RGS proteins are negative regulators of signaling through heterotrimeric G protein-coupled receptors and, as such, are in a position to regulate a plethora of biological phenomena. However, those have just begun to be explored in vivo. Here, we describe a mouse line deficient for Rgs4, a gene normally expressed early on in discrete populations of differentiating neurons and later on at multiple sites of the central nervous system, the cortex in particular, where it is one of the most highly transcribed Rgs genes. Rgs4(lacZ/lacZ) mice had normal neural development and were viable and fertile. Behavioral testing on mutant adults revealed subtle sensorimotor deficits but, so far, supported neither the proposed status of Rgs4 as a schizophrenia susceptibility gene (by showing intact prepulse inhibition in the mutants) nor (unlike another member of the Rgs family, Rgs9) a role of Rgs4 in the acute or chronic response to opioids.

Olfactory classical conditioning in newborn mice

Determining the behavioural phenotype of genetically altered mice is a valuable approach for elucidating the function of genes and their role in cognitive disorders. Methods for phenotyping newborn mice are scarce and generally confined to sensorimotor reflexes. Here, we describe a simple method for assessing associative abilities in newborn mice. We used a two-odour-choice classical conditioning paradigm in mice from the day of birth (post-natal age 0, P0) to P6. Acquisition required 20 trials: 10 trials during which the pups were placed over the conditioned stimulus (CS+) odour (lemon or peppermint) for 30s and simultaneously stroked gently with a paintbrush and 10 trials during which the pups were placed over the other odour (CS-) for 30s, without stroking. Then, the pups were subjected to five odour-preference trials to test for conditioning. This sequence of five trials was repeated after 5 and 24h to assess retention of the conditioned odour preference. During the immediate post-acquisition sequence, the pups spent significantly more time over the CS+ than over the CS- (p<0.0001). No extinction of the conditioned preference was observed during this test. No preference was observed after 5 or 24h, indicating that the conditioned response was promptly lost. Conditioning was effective as soon as P0-P1. Thus, conditioning may emerge in newborn mice sooner than previously reported. This paradigm is well suited to phenotyping of large samples of genetically altered mice and may shed light on the role for genes in paediatric cognitive impairments.

Neurobehavioral characterization of APP23 transgenic mice with the SHIRPA primary screen

The SHIRPA primary screen comprises 40 measures covering various reflexes and basic sensorimotor functions. This multi-test battery was used to compare non-transgenic controls with APP23 transgenic mice, expressing the 751 isoform of human beta-amyloid precursor protein and characterized by amyloid deposits in parenchyma and vessel walls. The APP23 mice were distinguishable from controls by pathological limb reflexes, myoclonic jumping, seizure activity, and tail malformation. In addition, this mouse model of Alzheimer's disease was also marked by a crooked swimming trajectory. APP23 mice were also of lighter weight and were less inclined to stay immobile during a transfer arousal test. Despite the neurologic signs, APP23 transgenic mice were not deficient in stationary beam, coat-hanger, and rotorod tests, indicating intact motor coordination abilities.

Rodent models for dystonia research: Characteristics, evaluation, and utility

A large number of different genetic and acquired disorders of the nervous system may be associated with dystonia. To elucidate its pathogenesis and to facilitate the discovery of potential novel treatments, there has been a growing interest in the development of animal models and particularly rodent models. Multiple animal models for dystonia have now been developed and partially characterized. The results obtained from studies of these models often lead in very different directions, in part because the different models target different aspects of a very heterogeneous disorder. A recent workshop addressed four main issues affecting those who conduct dystonia research with animal models, including the different ways in which dystonic disorders can be modeled in rodents, key features that constitute a useful model, methods used in the evaluation of these models, and recommendations for future research. This review summarizes the main outcomes of this conference. 2005 Movement Disorder Society.

Using ontologies to describe mouse phenotypes

By combining ontologies from different sources the authors developed a novel approach to describing phenotypes of mutant mice in a standard, structured manner.

The mouse is an important model of human genetic disease. Describing phenotypes of mutant mice in a standard, structured manner that will facilitate data mining is a major challenge for bioinformatics. Here we describe a novel, compositional approach to this problem which combines core ontologies from a variety of sources. This produces a framework with greater flexibility, power and economy than previous approaches. We discuss some of the issues this approach raises.

Characterization of hemizygous SOD1/wild-type transgenic mice with the SHIRPA primary screen and tests of sensorimotor function and anxiety

SOD1 is one of several overexpressed genes in Down's syndrome. In order to dissect genetic causes of the syndrome, hemizygous human wild-type SOD1 transgenic mice were compared to FVB/N non-transgenic controls at 3 months of age in the SHIRPA primary screen of neurologic function as well as in tests of motor activity and coordination. The responsiveness of SOD1/wt transgenic mice to visual and somatosensory stimuli was reduced in placing, pinna, corneal, and toe-pinch tests. In addition, SOD1/wt transgenic mice crossed fewer segments on a stationary beam. On the contrary, there was no intergroup difference for motor activity and anxiety in open-field and emergence tests and for latencies before falling on the stationary beam, coat-hanger, and rotorod. These results indicate mild deficits in sensorimotor responsiveness in a mouse model expressing human SOD1 and that the overexpressed gene may be responsible for some Down symptoms.

Impact of environmental housing conditions on the emotional responses of mice deficient for nociceptin/orphanin FQ peptide precursor gene

Nociceptin/orphanin FQ (N/OFQ) is a newly discovered neuropeptide that has been implicated in the neurobiological regulation of the behavioral responses to stress and fear. To investigate the role of this peptide in the expression of stress/anxiety-related behaviors in mice, a gene targeting approach to disrupt N/OFQ in the pre-proN/OFQ gene was used. The impact of environmental housing conditions (single and social housing) was assessed on N/OFQ-knockout male and female mice in different experimental paradigms known to trigger distinctive types of stress and anxiety states. Neurological examination of homozygous mutant adult animals indicated that basic neurological functions (vision, audition, olfaction, tactile and pain sensitivity, motor performances) were normal. When housed individually, N/OFQ-knockout animals displayed responses similar to control animals in behavioral tests of emotional reactivity (behavioral despair, locomotor activity, light-dark preference, and acoustic startle tests). In contrast, increased emotional responses were detected when individually housed mice were crowded together (five per cage) under conditions of competitive access to food, water, space, and social contacts. Under those conditions, male mice deficient for N/OFQ developed greater home-cage aggression and increased fear/anxiety-like behaviors in the light-dark and acoustic startle tests, when compared to their wild-type littermates. Group-housed female mutants also showed higher level of anxiety in the acoustic startle test, but needed additional restrain stress to express detectable levels of anxiety in the light-dark test. These data indicate a clear environment-induced rise in fear reactions of N/OFQ-knockout mice. They further suggest that N/OFQ system is essential for development of adequate coping strategies to acute and chronic stress.

SEE locomotor behavior test discriminates C57BL/6J and DBA/2J mouse inbred strains across laboratories and protocol conditions

Conventional tests of behavioral phenotyping frequently have difficulties differentiating certain genotypes and replicating these differences across laboratories and protocol conditions. This study explores the hypothesis that automated tests can be designed to quantify ethologically relevant behavior patterns that more readily characterize heritable and replicable phenotypes. It used SEE (Strategy for the Exploration of Exploration) to phenotype the locomotor behavior of the C57BL/6 and DBA/2 mouse inbred strains across 3 laboratories. The 2 genotypes differed in 15 different measures of behavior, none of which had a significant genotype-laboratory interaction. Within the same laboratory, most of these differences were replicated in additional experiments despite the test photoperiod phase being changed and saline being injected. Results suggest that well-designed tests may considerably enhance replicability across laboratories.

Characterization of NFH-LacZ transgenic mice with the SHIRPA primary screening battery and tests of motor coordination, exploratory activity, and spatial learning

NFH-LacZ transgenic mice express a fusion protein between a truncated form of the endogenous neurofilament of heavy molecular weight and the complete E. coli beta-galactosidase. NFH-LacZ transgenic mice could be distinguished from controls in the SHIRPA neurological battery by the appearance of action tremor and hindlimb clasping and a lower body weight. Despite normal exploratory activity and spatial learning, NFH-LacZ transgenic mice were deficient in stationary beam, coat-hanger, and rotorod tests of motor coordination. These results are concordant with neuropathological findings in spinal motoneurons and the cerebellum and indicate that despite the absence of paralysis, these transgenic mice may serve as an experimental model of the early stage of amyotrophic lateral sclerosis.

Behavioural phenotyping of mouse mutants

Behavioural phenotyping of mouse mutants is not a goal in itself but serves to characterise the behavioural effects of naturally occurring or experimentally induced mutations. Genetically engineered mouse mutants are valuable tools to elucidate the genetic control of behaviour and the interaction between genetic and environmental factors. However, a prerequisite for their use is the ability to assess different elements of behaviour. To this end, a battery of tests, which should be flexible enough to meet the needs of a particular study, should be used to characterise the behavioural phenotype. Detailed and extensive information about the effects of gene mutations is crucial for model building and model evaluation. Model building is an iterative process, switching between experimental data and theory formation. In order to facilitate this process and to allow comparison of results within and between laboratories, the standardisation of breeding, housing, and testing conditions is essential. The development and standardisation of sensitive, valid behavioural tests which are suited to phenotype mouse mutants is both a responsibility and a challenge to investigators of mouse behaviour.