Magnetic resonance imaging reveals specific anatomical changes in the brain of Agat- and Gamt-mice attributed to creatine depletion and guanidinoacetate alteration.

Arginine:glycine amidinotransferase- and guanidinoacetate methyltransferase deficiency are severe neurodevelopmental disorders. It is not known whether mouse models of disease express a neuroanatomical phenotype. High-resolution magnetic resonance imaging (MRI) with advanced image analysis was performed in perfused, fixed mouse brains encapsulated with the skull from male, 10-12 week old Agat -exc and B6J.Cg-Gamt tm1Isb mice (n = 48; n = 8 per genotype, strain). T2-weighted MRI scans were nonlinearly aligned to a 3D atlas of the mouse brain with 62 structures identified. Local differences in brain shape related to genotype were assessed by analysis of deformation fields. Creatine (Cr) and guanidinoacetate (GAA) were measured with high-performance liquid chromatography (HPLC) in brain homogenates (n = 24; n = 4 per genotype, strain) after whole-body perfusion. Cr was decreased in the brain of Agat- and Gamt mutant mice. GAA was decreased in Agat-/- and increased in Gamt-/- . Body weight and brain volume were lower in Agat-/- than in Gamt-/- . The analysis of entire brain structures revealed corpus callosum, internal capsule, fimbria and hypothalamus being different between the genotypes in both strains. Eighteen and fourteen significant peaks (local areas of difference in relative size) were found in Agat- and Gamt mutants, respectively. Comparing Agat-/- with Gamt-/- , we found changes in three brain regions, lateral septum, amygdala, and medulla. Intra-strain differences in four brain structures can be associated with Cr deficiency, while the inter-strain differences in three brain structures of the mutant mice may relate to GAA. Correlating these neuroanatomical findings with gene expression data implies the role of Cr metabolism in the developing brain and the importance of early intervention in patients with Cr deficiency syndromes.

Region-specific changes in Mus musculus brain size and cell composition under chronic nutrient restriction.

Nutrition is one of the most influential environmental factors affecting the development of different tissues and organs. It is suggested that under nutrient restriction the growth of the brain is spared as a result of the differential allocation of resources from other organs. However, it is not clear whether this sparing occurs brain-wide. Here, we analyzed morphological changes and cell composition in different regions of the offspring mouse brain after maternal exposure to nutrient restriction during pregnancy and lactation. Using high-resolution magnetic resonance imaging, we found that brain regions were differentially sensitive to maternal protein restriction and exhibited particular patterns of volume reduction. The cerebellum was reduced in absolute and relative volume, while cortex volume was relatively preserved. Alterations in cell composition (examined by the isotropic fractionator method) and organization of white matter (measured by diffusor tensor images) were also region specific. These changes were not related to the metabolic rate of the regions and were only partially explained by their specific growth trajectories. This study is a first step towards understanding the mechanisms of regional brain sparing at microstructural and macrostructural levels resulting from undernutrition.

Variability of brain anatomy for three common mouse strains.

The way in which brain structures express different morphologies is not fully understood. Here we investigate variability in brain anatomy using ex vivo MRI of three common laboratory mouse strains: in two inbred strains (C57BL/6 and 129S6) and one outbred strain (CD-1). We use Generalised Procrustes Analysis (GPA) to estimate modes of anatomical variability. We find three distinct bilateral modes of anatomical surface variability associated with the motor cortex, the anterior somatosensory, the retrosplenial and the entorhinal cortex. The modes of variability that are associated with the motor cortex and anterior somatosensory cortex are predominantly due to genetic, i.e. strain differences. Next, we specifically test if a particular strain is more variable. We find that only the mode associated with motor cortex size has a slightly larger variance in the outbred CD-1 mice compared to the two inbred strains. This suggests that the hypothesis that outbred strains are more variable in general is not true for brain anatomy and the use of outbred CD-1 mice does probably not come at the price of increased variability. Further, we show that the first two principal components distinguish between the three strains with 91% accuracy. This indicates that neuroanatomical strain differences are captured by considerably fewer dimensions than necessary for atlas-based or voxel-wise testing. Statistical comparisons based on shape models could thus be a powerful complement to traditional atlas and voxel-based methods at detecting gene-related brain differences in mice. Finally, we find that the principal components of individual brain structures are correlated, suggesting a tightly coupled network of interdependent developmental trajectories. These results raise the question to what degree neuroanatomical variability is directly genetically determined or the result of experience and epigenetic mechanisms.

Complex interplay between brain function and structure during cerebral amyloidosis in APP transgenic mouse strains revealed by multi-parametric MRI comparison.

Alzheimer's disease is a fatal neurodegenerative disorder affecting the aging population. Neuroimaging methods, in particular magnetic resonance imaging (MRI), have helped reveal alterations in the brain structure, metabolism, and function of patients and in groups at risk of developing AD, yet the nature of these alterations is poorly understood. Neuroimaging in mice is attractive for investigating mechanisms underlying functional and structural changes associated with AD pathology. Several preclinical murine models of AD have been generated based on transgenic insertion of human mutated APP genes. Depending on the specific mutations, mouse strains express different aspects of amyloid pathology, e.g. intracellular amyloid-ß (Aß) aggregates, parenchymal plaques, or cerebral amyloid angiopathy. We have applied multi-parametric MRI in three transgenic mouse lines to compare changes in brain function with resting-state fMRI and structure with diffusion tensor imaging and high resolution anatomical imaging. E22ΔAß developing intracellular Aß aggregates did not present functional or structural alterations compared to their wild-type littermates. PSAPP mice displaying parenchymal amyloid plaques displayed mild functional changes within the supplementary and barrel field cortices, and increased isocortical volume relative to controls. Extensive reduction in functional connectivity in the sensory-motor cortices and within the default mode network, as well as local volume increase in the midbrain relative to wild-type have been observed in ArcAß mice bearing intracellular Aß aggregates as well as parenchymal and vascular amyloid deposits. Patterns of functional and structural changes appear to be strain-specific and not directly related to amyloid deposition.

ENU-induced mutation in the DNA-binding domain of KLF3 reveals important roles for KLF3 in cardiovascular development and function in mice.

KLF3 is a Krüppel family zinc finger transcription factor with widespread tissue expression and no previously known role in heart development. In a screen for dominant mutations affecting cardiovascular function in N-ethyl-N-nitrosourea (ENU) mutagenized mice, we identified a missense mutation in the Klf3 gene that caused aortic valvular stenosis and partially penetrant perinatal lethality in heterozygotes. All homozygotes died as embryos. In the first of three zinc fingers, a point mutation changed a highly conserved histidine at amino acid 275 to arginine (Klf3(H275R) ). This change impaired binding of the mutant protein to KLF3's canonical DNA binding sequence. Heterozygous Klf3(H275R) mutants that died as neonates had marked biventricular cardiac hypertrophy with diminished cardiac chambers. Adult survivors exhibited hypotension, cardiac hypertrophy with enlarged cardiac chambers, and aortic valvular stenosis. A dominant negative effect on protein function was inferred by the similarity in phenotype between heterozygous Klf3(H275R) mutants and homozygous Klf3 null mice. However, the existence of divergent traits suggested the involvement of additional interactions. We conclude that KLF3 plays diverse and important roles in cardiovascular development and function in mice, and that amino acid 275 is critical for normal KLF3 protein function. Future exploration of the KLF3 pathway provides a new avenue for investigating causative factors contributing to cardiovascular disorders in humans.

A gestational ketogenic diet alters maternal metabolic status as well as offspring physiological growth and brain structure in the neonatal mouse.

BACKGROUND: The use of the ketogenic diet (KD) among women of child-bearing age has been increasing, leading to increased interest in identifying the diet's suitability during gestation. To date, no studies have thoroughly investigated the effect of a gestational KD on offspring growth. Since ketones have been reported to play a role in cerebral lipid and myelin synthesis, it is particularly important to investigate the diet's impact on brain anatomy of the offspring. METHODS: To fill this knowledge gap we imaged CD-1 mouse neonates whose mothers were fed either a standard diet (SD) or a KD prior to and during gestation. Images were collected at postnatal (P) 11.5 and 21.5 using Magnetic Resonance Imaging (MRI). Maternal metabolic status was also tracked during lactation, by following their body weight, blood glucose, ketone, cholesterol, and triglyceride concentrations. RESULTS: The KD dams exhibit a significant reduction in maternal fertility and litter size, as well as a high risk of developing fatal ketoacidosis by mid-lactation. To increase survival of the KD dams and offspring, fostering of P2.5 pups (from both KD and SD litters) by SD-foster dams was carried out. This resulted in stabilization of blood ketones of the KD dams, and aversion of the fatal ketoacidosis. We also note a slower and smaller weight loss for the KD compared with the SD dams. The average fostered KD pup exhibits retarded growth by P21.5 compared with the average fostered SD pup. An anatomical comparison of their brains further revealed significant structural differences at P11.5, and particularly at P21.5. The KD brain shows a relative bilateral decrease in the cortex, fimbria, hippocampus, corpus callosum and lateral ventricle, but a relative volumetric enlargement of the hypothalamus and medulla. CONCLUSION: A gestational ketogenic diet deleteriously affects maternal fertility and increases susceptibility to fatal ketoacidosis during lactation. Prenatal and early postnatal exposure to a ketogenic diet also results in significant alterations to neonatal brain structure, and results in retarded physiological growth. These alterations could be accompanied by functional and behavioural changes in later postnatal life.

Effects of a ketogenic diet during pregnancy on embryonic growth in the mouse.

BACKGROUND: The increasing use of the ketogenic diet (KD), particularly by women of child-bearing age, raises a question about its suitability during gestation. To date, no studies have thoroughly investigated the direct implications of a gestational ketogenic diet on embryonic development. METHODS: To fill this knowledge gap we imaged CD-1 mouse embryos whose mothers were fed either a Standard Diet (SD) or a KD 30 days prior to, as well as during gestation. Images were collected at embryonic days (E) 13.5 using Optical Projection Tomography (OPT) and at E17.5 using Magnetic Resonance Imaging (MRI). RESULTS: An anatomical comparison of the SD and KD embryos revealed that at E13.5 the average KD embryo was volumetrically larger, possessed a relatively larger heart but smaller brain, and had a smaller pharynx, cervical spinal cord, hypothalamus, midbrain, and pons, compared with the average SD embryo. At E17.5 the KD embryo was found to be volumetrically smaller with a relatively smaller heart and thymus, but with enlarged cervical spine, thalamus, midbrain and pons. CONCLUSION: A ketogenic diet during gestation results in alterations in embryonic organ growth. Such alterations may be associated with organ dysfunction and potentially behavioral changes in postnatal life.

Nestin is not essential for development of the CNS but required for dispersion of acetylcholine receptor clusters at the area of neuromuscular junctions.

Nestin is expressed in many different progenitors during development including those of the CNS, heart, skeletal muscle, and kidney. The adult expression is mainly restricted to the subependymal zone and dentate gyrus of the brain, the neuromuscular junction, and renal podocytes. In addition, this intermediate filament protein has served as a marker of neural stem/progenitor cells for close to 20 years. Therefore it is surprising that its function in development and adult physiology is still poorly understood. Here we report that nestin deficiency is compatible with normal development of the CNS. The mutant mice, however, show impaired motor coordination. Furthermore, we found that the number of acetylcholine receptor clusters, the nerve length, and the endplate bandwidth are significantly increased in neuromuscular junction area of nestin-deficient mice. This is similar to the phenotype described for deficiency of cyclin-dependent kinase 5 (Cdk5), a candidate downstream affecter of nestin. Moreover, we demonstrate that nestin deficiency can rescue maintenance of acetylcholine receptor clusters in the absence of agrin, similar to Cdk5/agrin double knock-outs, suggesting that the observed nestin deficiency phenotype is the consequence of aberrant Cdk5 activity.

Spontaneous adult-onset pulmonary arterial hypertension attributable to increased endothelial oxidative stress in a murine model of hereditary hemorrhagic telangiectasia.

OBJECTIVE: Loss-of-function mutations in genes coding for transforming growth factor-beta/bone morphogenetic protein receptors and changes in nitric oxide(*) (NO(*)) bioavailability are associated with hereditary hemorrhagic telangiectasia and some forms of pulmonary arterial hypertension. How these abnormalities lead to seemingly disparate pulmonary pathologies remains unknown. Endoglin (Eng), a transforming growth factor-beta coreceptor, is mutated in hereditary hemorrhagic telangiectasia and involved in regulating endothelial NO(*) synthase (eNOS)-derived NO(*) production and oxidative stress. Because some patients with pulmonary arterial hypertension harbor ENG mutations leading to haplo insufficiency, we investigated the pulmonary vasculature of Eng(+/-) mice and the potential contribution of abnormal eNOS activation to pulmonary arterial hypertension. METHODS AND RESULTS: Hemodynamic, histological, and biochemical assessments and x-ray micro-CT imaging of adult Eng(+/-) mice indicated signs of pulmonary arterial hypertension including increased right ventricular systolic pressure, degeneration of the distal pulmonary vasculature, and muscularization of small arteries. These findings were absent in 3-week-old Eng(+/-) mice and were attributable to constitutively uncoupled eNOS activity in the pulmonary circulation, as evidenced by reduced eNOS/heat shock protein 90 association and increased eNOS-derived superoxide ((*)O(2)(-)) production in a BH(4)-independent manner. These changes render eNOS unresponsive to regulation by transforming growth factor-beta/bone morphogenetic protein and underlie the signs of pulmonary arterial hypertension that were prevented by Tempol. CONCLUSIONS: Adult Eng(+/-) mice acquire signs of pulmonary arterial hypertension that are attributable to uncoupled eNOS activity and increased (*)O(2)(-) production, which can be prevented by antioxidant treatment. Eng links transforming growth factor/bone morphogenetic protein receptors to the eNOS activation complex, and its reduction in the pulmonary vasculature leads to increased oxidative stress and pulmonary arterial hypertension.

Neurobiological Mechanisms of Chemotherapy-induced Cognitive Impairment in a Transgenic Model of Breast Cancer.

Animal studies have reinforced clinical reports of cognitive impairment in cancer survivors following chemotherapy but, until now, all pre-clinical research in this area has been conducted on normal rodents. The present study investigated the effects of chemotherapy on cognition and underlying biological mechanisms in the FVB/N-Tg (MMTV-neu) 202 Mul/J mouse, a well-characterized transgenic model of breast cancer that has similarities to the tumorigenesis which occurs in humans. Tumor-bearing and control mice received three weekly injections of a combination of methotrexate + 5-fluorouracil, or an equal volume of saline. Different aspects of learning and memory were measured before and after treatment. The effects of tumor and chemotherapy on neurogenesis, neuro-inflammatory cytokine activity, and brain volume, as they relate to corresponding cognitive changes, were also measured. The toxic effects of chemotherapy extended to the cancerous model in which substantial cognitive impairment was also associated with the disease. Cognitive deficits were greatest in tumorigenic mice that received the anti-cancer drugs. Both tumor growth and chemotherapy caused significant changes in brain volume, including the hippocampus and frontal lobes, two structures that are directly implicated in cognitive tasks that were shown to be vulnerable. The level of hippocampal neurogenesis in adulthood was suppressed in chemotherapy-treated mice and associated with loss of hippocampus-controlled cognitive function. Dysregulation of cytokine activity was found in tumorigenic mice and associated with impaired cognitive performance. The results show that chemotherapy and tumor development independently contribute to cognitive deficits through different biological mechanisms.

Integrin-linked kinase expression is elevated in human cardiac hypertrophy and induces hypertrophy in transgenic mice.

BACKGROUND: Although numerous signaling pathways are known to be activated in experimental cardiac hypertrophy, the molecular basis of the hypertrophic response inherent in human heart diseases remains largely unknown. Integrin-linked kinase (ILK) is a multifunctional protein kinase that physically links beta-integrins with the actin cytoskeleton, suggesting a potential mechanoreceptor role. METHODS AND RESULTS: Here, we show a marked increase in ILK protein levels in hypertrophic ventricles of patients with congenital and acquired outflow tract obstruction. This increase in ILK was associated with activation of the Rho family guanine triphosphatases, Rac1 and Cdc42, and known hypertrophic signaling kinases, including extracellular signal-related kinases (ERK1/2) and p70 S6 kinase. Transgenic mice with cardiac-specific expression of a constitutively active ILK (ILK(S343D)) or wild-type ILK (ILK(WT)) exhibited a compensated ventricular hypertrophic phenotype and displayed an activation profile of guanine triphosphatases and downstream protein kinases concordant with that seen in human hypertrophy. In contrast, transgenic mice with cardiomyocyte-restricted expression of a kinase-inactive ILK (ILK(R211A)) were unable to mount a compensatory hypertrophic response to angiotensin II in vivo. CONCLUSIONS: Taken together, these results identify ILK-regulated signaling as a broadly adaptive hypertrophic response mechanism relevant to a wide range of clinical heart disease.

Gestational ketogenic diet programs brain structure and susceptibility to depression & anxiety in the adult mouse offspring.

INTRODUCTION: The ketogenic diet (KD) has seen an increase in popularity for clinical and non-clinical purposes, leading to rise in concern about the diet's impact on following generations. The KD is known to have a neurological effect, suggesting that exposure to it during prenatal brain development may alter neuro-anatomy. Studies have also indicated that the KD has an anti-depressant effect on the consumer. However, it is unclear whether any neuro-anatomical and/or behavioral changes would occur in the offspring and persist into adulthood. METHODS: To fill this knowledge gap we assessed the brain morphology and behavior of 8-week-old young-adult CD-1 mice, who were exposed to the KD in utero, and were fed only a standard-diet (SD) in postnatal life. Standardized neuro-behavior tests included the Open-Field, Forced-Swim, and Exercise Wheel tests, and were followed by post-mortem Magnetic Resonance Imaging (MRI) to assess brain anatomy. RESULTS: The adult KD offspring exhibit reduced susceptibility to anxiety and depression, and elevated physical activity level when compared with controls exposed to the SD both in utero and postnatally. Many neuro-anatomical differences exist between the KD offspring and controls, including, for example, a cerebellar volumetric enlargement by 4.8%, a hypothalamic reduction by 1.39%, and a corpus callosum reduction by 4.77%, as computed relative to total brain volume. CONCLUSIONS: These results suggest that prenatal exposure to the KD programs the offspring neuro-anatomy and influences their behavior in adulthood.

Inflection Points in Magnetic Resonance Imaging Technology-35 Years of Collaborative Research and Development.

The technology for clinical magnetic resonance imaging (MRI) has advanced with remarkable speed and in such a manner reflecting the influence of 3 forces-collaboration between disciplines, collaboration between academia and industry, and the enabling of software applications by hardware. The forces are evident in the key developments from the past and emerging trends for the future highlighted in this review article. These developments are associated with MRI system attributes, such as wider, shorter, and stronger magnets; specialty magnets and hybrid devices; k space; and the notion that magnetic field gradients perform a Fourier transform on the spatial distribution of magnetization, phased-array coils and parallel imaging, the user interface, the wide range of contrast possible, and applications that exploit motion-induced phase shifts. An attempt is made to show connections between these developments and how the 3 forces mentioned previously will continue to shape the technology used so productively in clinical MRI.

Neuroanatomical Phenotypes Are Consistent With Autism-Like Behavioral Phenotypes in the 15q11-13 Duplication Mouse Model.

Paternally and maternally inherited deletions and duplications of human chromosome 15q11-13 are relatively common in the human population. Furthermore, duplications in the 15q region are often associated with autism. Both maternal and paternal interstitial 15q11-13 duplication mouse models have been previously created, where several behavioral differences were found in the paternal duplication (patDp/+) mouse but not in the maternal duplication (matDp/+). These included decreased sociability, behavioral inflexibility, abnormal ultrasonic vocalizations, decreased spontaneous activity, and increased anxiety. Similarly, in the current study, we found several anatomical differences in the patDp/+ mice that were not seen in the matDp/+ mice. Regional differences that are evident only in the paternal duplication are a smaller dentate gyrus and smaller medial striatum. These differences may be responsible for the behavioral inflexibility. Furthermore, a smaller dorsal raphe nucleus could be responsible for the reported serotonin defects. This study highlights consistency that can be found between behavioral and anatomical phenotyping.

Transit time kinetics in ordered and disordered vascular trees.

Imaging modalities exploit tracer-dilution methods to measure bulk haemodynamic parameters such as blood flow and volume at the level of the microcirculation. Here, we ask the question of whether the kinetics of a tracer can reveal morphological information about the vessels through which the tracers flow. The goal is to relate the acquired time-intensity characteristic to details of the vascular structure that lies below the imaging resolution. Two fractal vascular models are developed that represent organized 'kidney-like' and disorganized 'tumour-like' structures. The models are generated using simple rules of branching and fractal geometry in two dimensions. Blood flow and tracer kinetics are simulated using fundamental laws of haemodynamics. The flow conditions are matched in the two models. The fractal box dimensions of the kidney (D(B) = 1.67 +/- 0.01) and the tumour (D(B) = 1.80 +/- 0.01) vasculatures fall in the range given in the literature (D(B) = 1.61 +/- 0.06 and D(B) = 1.84 +/- 0.04, respectively). The tracer kinetic curves of the kidney and the tumour vasculatures have the same initial slope and final asymptote, corresponding to the same flow rate and vascular volume, but have different forms. The difference in the two curves is related to the distribution function of transit times of the vascular models, and is a consequence of the randomness introduced in vessel diameter and length. In principle, the form of the tracer kinetic curve from a contrast imaging study may offer information relating not only to vascular volume and flow rate, but also to the organization of a microvascular network.

Imaging of murine brain tumors using a 1.5 Tesla clinical MRI system.

BACKGROUND: In this study, we investigated the feasibility of using a 1.5 Tesla (T) clinical magnetic resonance imaging (MRI) system for in vivo assessment of three histopathologically different brain tumor models in mice. METHODS: We selected mouse models in which tumor growth was observed in different intracranial compartments: Patched+/- heterozygous knock-out mice for tumor growth in the cerebellum (n = 5); U87 MG human astrocytoma cells xenografted to the frontal lobe of athymic mice (n = 15); and F5 (n = 15) or IOMM Lee (n = 15) human malignant meningioma cells xenotransplanted to the athymic mouse skull base or convexity. Mice were imaged using a small receiver surface coil and a clinical 1.5 T MRI system. T1- and fast spin echo T2-weighted image sequences were obtained in all animals. Gadolinium was injected via tail vein to better delineate the intracranial tumors. Twenty mice were followed by serial MRI to study tumor growth over time. In these mice, images were typically performed after tumor implantation, and at two week intervals. Mice were euthanized following their last imaging procedure, and their tumors were examined by histopathology. The histopathological preparations were then compared to the last MR images to correlate the imaging features with the pathology. RESULTS: Magnetic resonance imaging delineated th tumors in the cerebellum, frontal lobes and skull base in all mouse models. The detection of intracranial tumors was enhanced with prio administration of gadolinium, and the limit of resolution of brain tumors in the mice was 1-2 mm3. Sequential images performed at different time intervals showed progressive tumor growth in all animals. The MR images of tumor size and location correlated accurately with th results of the histopathological analysis. CONCLUSION: Magnetic resonance imaging of murine brain tumors in different intracrania compartments is feasible with a 1.5 T clinical MR system and a specially designed surface coil. Tumors as small as 1-2 mm3 can be detecte with good image resolution. Mice harbouring nascent brain tumors can be followed sequentially by serial MR imaging. This may allow for a noninvasive means by which tumor growth can be measured, and novel therapies tested without resorting to sacrifice of the mice.

Behavioral abnormalities and circuit defects in the basal ganglia of a mouse model of 16p11.2 deletion syndrome.

A deletion on human chromosome 16p11.2 is associated with autism spectrum disorders. We deleted the syntenic region on mouse chromosome 7F3. MRI and high-throughput single-cell transcriptomics revealed anatomical and cellular abnormalities, particularly in cortex and striatum of juvenile mutant mice (16p11(+/-)). We found elevated numbers of striatal medium spiny neurons (MSNs) expressing the dopamine D2 receptor (Drd2(+)) and fewer dopamine-sensitive (Drd1(+)) neurons in deep layers of cortex. Electrophysiological recordings of Drd2(+) MSN revealed synaptic defects, suggesting abnormal basal ganglia circuitry function in 16p11(+/-) mice. This is further supported by behavioral experiments showing hyperactivity, circling, and deficits in movement control. Strikingly, 16p11(+/-) mice showed a complete lack of habituation reminiscent of what is observed in some autistic individuals. Our findings unveil a fundamental role of genes affected by the 16p11.2 deletion in establishing the basal ganglia circuitry and provide insights in the pathophysiology of autism.

Evaluation of bi-ventricular coronary flow patterns using high-frequency ultrasound in mice with transverse aortic constriction.

Using high-frequency color and pulsed Doppler ultrasound, we evaluated the flow patterns of the left (LCA), septal (SCA) and right (RCA) coronary arteries in mice with and without transverse aortic constriction (TAC). Fifty-two male C57BL/6J mice were subjected to TAC or a corresponding sham operation. At 2 and 8 wk post-surgery, Doppler flow spectra from the three coronary arteries, together with morphologic and functional parameters of the left and right ventricles, were measured. Histology was performed to evaluate myocyte size and neo-angiogenesis in both ventricles. In sham-operated mice, the LCA and SCA both exhibited low-flow waveforms during systole and dominantly higher-flow waveforms during diastole. The RCA exhibited generally lower flow velocity, with similar systolic and diastolic waveforms. TAC significantly increased the systolic flow velocities of all coronary arteries, but enhanced the flow mainly in the LCA and SCA. In the left ventricle, coronary flow reserve was partially preserved 2 wk post-TAC, but decreased at 8 wk, consistent with changes in neo-angiogenesis and systolic function. In contrast, no significant change was found in the coronary flow reserve, structure or function of the right ventricle. This study has established a protocol for evaluating the flow pattern in three principal coronary arteries in mice using Doppler ultrasound and illustrated the difference among three vessels at baseline. In mice with TAC, the difference in the associating pattern of coronary flow dynamics with the myocardial structure and function between the left and right ventricles provides further insights into ventricular remodeling under pressure overload.

Effects of repeated adolescent stress and serotonin transporter gene partial knockout in mice on behaviors and brain structures relevant to major depression.

In humans, exposure to stress during development is associated with structural and functional alterations of the prefrontal cortex (PFC), amygdala (AMY), and hippocampus (HC) and their circuits of connectivity, and with an increased risk for developing major depressive disorder particularly in carriers of the short (s) variant of the serotonin transporter (5-HTT) gene-linked polymorphic region (5-HTTLPR). Although changes in these regions are found in carriers of the s allele and/or in depressed patients, evidence for a specific genotype × developmental stress effect on brain structure and function is limited. Here, we investigated the effect of repeated stress exposure during adolescence in mice with partial knockout of the 5-HTT gene (HET) vs. wildtype (WT) on early-adulthood behavioral measures and brain structure [using magnetic resonance imaging (MRI)] relevant to human major depression. Behaviorally, adolescent stress (AS) increased anxiety and decreased activity and did so to a similar degree in HET and WT. In a probabilistic reversal learning task, HET-AS mice achieved fewer reversals than did HET-No-AS mice. 5-HTT genotype and AS were without effect on corticosterone stress response. In terms of structural brain differences, AS reduced the volume of two long-range white matter tracts, the optic tract (OT) and the cerebral peduncle (CP), in WT mice specifically. In a region-of-interest analysis, AS was associated with increased HC volume and HET genotype with a decreased frontal lobe volume. In conclusion, we found that 5-HTT and AS genotype exerted long-term effects on behavior and development of brain regions relevant to human depression.

Bloomsbury report on mouse embryo phenotyping: recommendations from the IMPC workshop on embryonic lethal screening.

Identifying genes that are important for embryo development is a crucial first step towards understanding their many functions in driving the ordered growth, differentiation and organogenesis of embryos. It can also shed light on the origins of developmental disease and congenital abnormalities. Current international efforts to examine gene function in the mouse provide a unique opportunity to pinpoint genes that are involved in embryogenesis, owing to the emergence of embryonic lethal knockout mutants. Through internationally coordinated efforts, the International Knockout Mouse Consortium (IKMC) has generated a public resource of mouse knockout strains and, in April 2012, the International Mouse Phenotyping Consortium (IMPC), supported by the EU InfraCoMP programme, convened a workshop to discuss developing a phenotyping pipeline for the investigation of embryonic lethal knockout lines. This workshop brought together over 100 scientists, from 13 countries, who are working in the academic and commercial research sectors, including experts and opinion leaders in the fields of embryology, animal imaging, data capture, quality control and annotation, high-throughput mouse production, phenotyping, and reporter gene analysis. This article summarises the outcome of the workshop, including (1) the vital scientific importance of phenotyping embryonic lethal mouse strains for basic and translational research; (2) a common framework to harmonise international efforts within this context; (3) the types of phenotyping that are likely to be most appropriate for systematic use, with a focus on 3D embryo imaging; (4) the importance of centralising data in a standardised form to facilitate data mining; and (5) the development of online tools to allow open access to and dissemination of the phenotyping data.