Heterozygous Mutant Mice Research Articles

The Mouse Homolog of DGCR2 Gene Encoding within 22q11.2 Contributes to Enchondral Ossification in Skull Base and Its Defect Causes the Severity in 22q11.2 Deletion Syndrome

Previously, we cloned the Sez12 gene, encoding a membrane protein, the expression of which immediately changed in mouse brain after convulsant drug-induced seizure 1. Nucleotide sequence analysis indicates the Sez12 is the mouse homolog of human DGCR2, which is encoded within the genome deletion region found in patients with 22q11.2 deletion syndrome (22q11.2 DS). The 22q11.2 DS is caused by haploinsufficiency in 22q11.2 and shows a wide spectrum of symptoms, including maxillofacial abnormalities. TBX1 is considered the most responsible gene within 22q11.2, encoding a T-box type transcription factor. Although the TBX1 mutation is found in some 22q11.2 patients, heterozygous Tbx1 mutant mice showed no obvious maxillofacial phenotype, suggesting composite and complex dysfunctions of genes, including TBX1. Since the membrane protein DGCR2 would play an important role in ligand-induced signal transduction involved in maxillofacial abnormalities, we hypothesize that the Dgcr2 is an attractive candidate for pathological severity of 22q11.2 DS.

Mechanism Sharing Between Genetic and Gestational Hypoxia-Induced Cardiac Anomalies.

Background: Cardiac development is a dynamic process both temporally and spatially. These complex processes are often disturbed and lead to congenital cardiac anomalies that affect approximately 1% of live births. Disease-causing variants in several genetic loci lead to cardiac anomalies, with variants in transcription factor NKX2-5 gene being one of the largest variants known. Gestational hypoxia, such as seen in high-altitude pregnancy, has been known to affect cardiac development, yet the incidence and underlying mechanisms are largely unknown.Methods and Results: Normal wild-type female mice mated with heterozygous Nkx2-5 mutant males were housed under moderate hypoxia (14% O2) or normoxia (20.9% O2) conditions from 10.5 days of gestation. Wild-type mice exposed to hypoxia demonstrate excessive trabeculation, ventricular septal defects, irregular morphology of interventricular septum as well as atrial septal abnormalities, which overlap with those seen in heterozygous Nkx2-5 mutant mice. Genome-wide transcriptome done by RNA-seq of a 2-day hypoxic exposure on wild-type embryos revealed abnormal transcriptomes, in which approximately 60% share those from Nkx2-5 mutants without hypoxia. Gestational hypoxia reduced the expression of Nkx2-5 proteins in more than one-half along with a reduction in phosphorylation, suggesting that abnormal Nkx2-5 function is a common mechanism shared between genetic and gestational hypoxia-induced cardiac anomalies, at least at a specific developing stage.Conclusion: The results of our study provide insights into a common molecular mechanism underlying non-genetic and genetic cardiac anomalies.

Muscarinic Agonist Ameliorates Insulin Secretion in Wfs1-Deficient Mice.

Similar to patients with Wolfram syndrome and to heterozygous Wolframin1 (Wfs1) mutation carriers, Wfs1-deficient mice exhibit impaired glucose tolerance and lower plasma insulin levels. Muscarinic receptor 3 agonists have previously been shown to potentiate glucose-stimulated insulin secretion. Therefore, the aim of this study was to investigate insulin-secretion dynamics in Wfs1-deficient mice and evaluate carbachol, muscarinic agonist and the ability to ameliorate the insulin secretion deficits caused by the Wfs1 mutation. Wild-type Wfs1 heterozygous and Wfs1 mutant mice were used. Blood glucose was measured after glucose and carbachol administration. Insulin secretion was measured from serum using ELISA. Glucose administration causes hyperglycemia in Wfs1-deficient mice due to decreased insulin secretion. This deficit is abolished by administration of the muscarinic agonist carbachol. Activation of the muscarinic pathway to potentiate insulin secretion may present a target to manage diabetes resulting from Wfs1 deficiency.

Altered Neocortical Gene Expression, Brain Overgrowth and Functional Over-Connectivity in Chd8 Haploinsufficient Mice.

Truncating CHD8 mutations are amongst the highest confidence risk factors for autism spectrum disorder (ASD) identified to date. Here, we report that Chd8 heterozygous mice display increased brain size, motor delay, hypertelorism, pronounced hypoactivity, and anomalous responses to social stimuli. Whereas gene expression in the neocortex is only mildly affected at midgestation, over 600 genes are differentially expressed in the early postnatal neocortex. Genes involved in cell adhesion and axon guidance are particularly prominent amongst the downregulated transcripts. Resting-state functional MRI identified increased synchronized activity in cortico-hippocampal and auditory-parietal networks in Chd8 heterozygous mutant mice, implicating altered connectivity as a potential mechanism underlying the behavioral phenotypes. Together, these data suggest that altered brain growth and diminished expression of important neurodevelopmental genes that regulate long-range brain wiring are followed by distinctive anomalies in functional brain connectivity in Chd8+/− mice. Human imaging studies have reported altered functional connectivity in ASD patients, with long-range under-connectivity seemingly more frequent. Our data suggest that CHD8 haploinsufficiency represents a specific subtype of ASD where neuropsychiatric symptoms are underpinned by long-range over-connectivity.

The Endocannabinoid System across Postnatal Development in Transmembrane Domain Neuregulin 1 Mutant Mice

The use of cannabis is a well-established component risk factor for schizophrenia, particularly in adolescent individuals with genetic predisposition for the disorder. Alterations to the endocannabinoid system have been found in the prefrontal cortex of patients with schizophrenia. Thus, we assessed whether molecular alterations exist in the endocannabinoid signalling pathway during brain development in a mouse model for the schizophrenia risk gene neuregulin 1 (Nrg1). We analysed transcripts encoding key molecules of the endocannabinoid system in heterozygous transmembrane domain Nrg1 mutant mice (Nrg1 TM HET), which is known to have increased sensitivity to cannabis exposure. Tissue from the prelimbic cortex and hippocampus of male and female Nrg1 TM HET mice and wild type-like littermates was collected at postnatal days (PNDs) 7, 10, 14, 21, 28, 35, 49, and 161. Quantitative polymerase chain reaction was conducted to assess mRNA levels of cannabinoid receptor 1 (CB1R) and enzymes for the synthesis and breakdown of the endocannabinoid 2-arachidonoylglycerol [i.e., diacylglycerol lipase alpha (DAGLα), monoglyceride lipase (MGLL), and α/β-hydrolase domain-containing 6 (ABHD6)]. No sex differences were found for any transcripts in either brain region; thus, male and female data were pooled. Hippocampal and cortical mRNA expression of DAGLα, MGLL, and ABHD6 increased until PND 21–35 and then decreased and stabilised for the rest of postnatal development. Hippocampal CB1R mRNA expression increased until PND 21 and decreased after this age. Expression levels of these endocannabinoid markers did not differ in Nrg1 TM HET compared to control mice at any time point. Here, we demonstrate dynamic changes in the developmental trajectory of several key endocannabinoid system transcripts in the mouse brain, which may correspond with periods of endocannabinoid system maturation. Nrg1 TM HET mutation did not alter the developmental trajectory of the endocannabinoid markers assessed, suggesting that other mechanisms may be responsible for the exaggerated cannabinoid susceptibility in these mice.

Targeted deletion of a 170-kb cluster of LINE-1 repeats and implications for regional control.

Approximately half the mammalian genome is composed of repetitive sequences, and accumulating evidence suggests that some may have an impact on genome function. Here, we characterized a large array class of repeats of long-interspersed elements (LINE-1). Although widely distributed in mammals, locations of such arrays are species specific. Using targeted deletion, we asked whether a 170-kb LINE-1 array located at a mouse imprinted domain might function as a modulator of local transcriptional control. The LINE-1 array is lamina associated in differentiated ES cells consistent with its AT-richness, and although imprinting occurs both proximally and distally to the array, active LINE-1 transcripts within the tract are biallelically expressed. Upon deletion of the array, no perturbation of imprinting was observed, and abnormal phenotypes were not detected in maternal or paternal heterozygous or homozygous mutant mice. The array does not shield nonimprinted genes in the vicinity from local imprinting control. Reduced neural expression of protein-coding genes observed upon paternal transmission of the deletion is likely due to the removal of a brain-specific enhancer embedded within the LINE array. Our findings suggest that presence of a 170-kb LINE-1 array reflects the tolerance of the site for repeat insertion rather than an important genomic function in normal development.

The Hajdu Cheney Mutation Is a Determinant of B-Cell Allocation of the Splenic Marginal Zone

The neurogenic locus notch homolog protein (Notch)-2 receptor is a determinant of B-cell allocation, and gain-of-NOTCH2-function mutations are associated with Hajdu-Cheney syndrome (HCS), a disease presenting with osteoporosis and acro-osteolysis. We generated a mouse model reproducing the HCS mutation (Notch2HCS), and heterozygous global mutant mice displayed gain-of-Notch2 function. In the mutant spleen, the characteristic perifollicular rim marking the marginal zone (MZ), which is the interface between the nonlymphoid red pulp and the lymphoid white pulp, merged with components of the white pulp. As a consequence, the MZ of Notch2HCS mice occupied most of the splenic structure. To explore the mechanisms involved, lymphocyte populations from the bone marrow and spleen were harvested from heterozygous Notch2HCS mice and sex-matched control littermates and analyzed by flow cytometry. Notch2HCS mice had an increase in CD21/35highCD23- splenic MZ B cells of approximately fivefold and a proportional decrease in splenic follicular B cells (CD21/35intCD23+) at 1, 2, and 12 months of age. Western blot analysis revealed that Notch2HCS mutant splenocytes had increased phospho-Akt and phospho-Jun N-terminal kinase, and gene expression analysis of splenic CD19+ B cells demonstrated induction of Hes1 and Hes5 in Notch2HCS mutants. Anti-Notch2 antibodies decreased MZ B cells in control and Notch2HCS mice. In conclusion, Notch2HCS mutant mice have increased mature B cells in the MZ of the spleen.

Standardized, systemic phenotypic analysis reveals kidney dysfunction as main alteration of Kctd1I27N mutant mice

BackgroundIncreased levels of blood plasma urea were used as phenotypic parameter for establishing novel mouse models for kidney diseases on the genetic background of C3H inbred mice in the phenotype-driven Munich ENU mouse mutagenesis project. The phenotypically dominant mutant line HST014 was established and further analyzed.MethodsAnalysis of the causative mutation as well as the standardized, systemic phenotypic analysis of the mutant line was carried out.ResultsThe causative mutation was detected in the potassium channel tetramerization domain containing 1 (Kctd1) gene which leads to the amino acid exchange Kctd1I27N thereby affecting the functional BTB domain of the protein. This line is the first mouse model harboring a Kctd1 mutation. Kctd1I27N homozygous mutant mice die perinatally. Standardized, systemic phenotypic analysis of Kctd1I27N heterozygous mutants was carried out in the German Mouse Clinic (GMC). Systematic morphological investigation of the external physical appearance did not detect the specific alterations that are described in KCTD1 mutant human patients affected by the scalp-ear-nipple (SEN) syndrome. The main pathological phenotype of the Kctd1I27N heterozygous mutant mice consists of kidney dysfunction and secondary effects thereof, without gross additional primary alterations in the other phenotypic parameters analyzed. Genome-wide transcriptome profiling analysis at the age of 4 months revealed about 100 differentially expressed genes (DEGs) in kidneys of Kctd1I27N heterozygous mutants as compared to wild-type controls.ConclusionsIn summary, the main alteration of the Kctd1I27N heterozygous mutants consists in kidney dysfunction. Additional analyses in 9–21 week-old heterozygous mutants revealed only few minor effects.

Pharmacological inhibition of Anaplastic Lymphoma Kinase rescues spatial memory impairments in Neurofibromatosis 1 mutant mice.

Heterozygous Neurofibromatosis 1 (NF1) loss of function mutations are found in 90% of patients with neurofibromatosis, a syndrome associated with disabling cognitive impairment. Drosophila studies have demonstrated a genetic interaction between Anaplastic Lymphoma Kinase (Alk) and NF1 in cognitive performance. In addition, pharmacologic inhibition of Alk improves cognitive performance in heterozygous NF1 mutant flies. In this study, we tested whether pharmacological inhibition of Alk in heterozygous NF1 mutant mice attenuates or rescues cognitive impairments. Cognitive impairment of spatial memory retention observed in heterozygous NF1 mutant mice was rescued by the Alk inhibitor. These data support the hypothesis that inhibition of Alk may cognitively benefit patients with Neurofibromatosis 1.

N‐ethyl‐N‐nitrosourea–Induced Adaptor Protein 2 Sigma Subunit 1 (Ap2s1) Mutations Establish Ap2s1 Loss‐of‐Function Mice

ABSTRACTThe adaptor protein‐2 sigma subunit (AP2σ), encoded by AP2S1, forms a heterotetrameric complex, with AP2α, AP2β, and AP2μ subunits, that is pivotal for clathrin‐mediated endocytosis, and AP2σ loss‐of‐function mutations impair internalization of the calcium‐sensing receptor (CaSR), a G‐protein–coupled receptor, and cause familial hypocalciuric hypercalcemia type‐3 (FHH3). Mice with AP2σ mutations that would facilitate investigations of the in vivo role of AP2σ, are not available, and we therefore embarked on establishing such mice. We screened >10,000 mice treated with the mutagen N‐ethyl‐N‐nitrosourea (ENU) for Ap2s1 mutations and identified 5 Ap2s1 variants, comprising 2 missense (Tyr20Asn and Ile123Asn) and 3 intronic base substitutions, one of which altered the invariant donor splice site dinucleotide gt to gc. Three‐dimensional modeling and cellular expression of the missense Ap2s1 variants did not reveal them to alter AP2σ structure or CaSR‐mediated signaling, but investigation of the donor splice site variant revealed it to result in an in‐frame deletion of 17 evolutionarily conserved amino acids (del17) that formed part of the AP2σ α1‐helix, α1‐β3 loop, and β3 strand. Heterozygous mutant mice (Ap2s1+/del17) were therefore established, and these had AP2σ haplosufficiency but were viable with normal appearance and growth. Ap2s1+/del17 mice, when compared with Ap2s1+/+ mice, also had normal plasma concentrations of calcium, phosphate, magnesium, creatinine, urea, sodium, potassium, and alkaline phosphatase activity; normal urinary fractional excretion of calcium, phosphate, sodium, and potassium; and normal plasma parathyroid hormone (PTH) and 1,25‐dihydroxyvitamin D (1,25(OH)2) concentrations. However, homozygous Ap2s1del17 /del 17 mice were non‐viable and died between embryonic days 3.5 and 9.5 (E3.5–9.5), thereby indicating that AP2σ likely has important roles at the embryonic patterning stages and organogenesis of the heart, thyroid, liver, gut, lungs, pancreas, and neural systems. Thus, our studies have established a mutant mouse model that is haplosufficient for AP2σ. © 2017 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

The role of MHC class II polymorphisms for DM-mediated peptide editing and autoimmunity

Abstract Polymorphisms in MHC class II (MHCII) genes are the strongest risk factors for the development of autoimmune diseases, such as type I diabetes (T1D). T1D is associated with allelic variants of the MHCII molecule HLA-DQ. In the nonobese diabetic (NOD) mouse, the orthologous molecule, I-Ag7, also predisposes mice to spontaneous diabetes development. To investigate the functional impact of natural MHCII polymorphisms on DM binding and T1D we introduced selected mutations in the genome of the NOD mouse by CRISPR/Cas9 genomic editing. Our approach was to first identify unique polymorphisms in the putative interface of I-Ag7, and then assess the impact of these polymorphisms on DM-mediated peptide editing in vitro. Several polymorphisms increased the interaction between I-Ag7 and DM and augmented peptide binding. The substitution of lysine (K) 40 in I-Aα with glutamic acid (E) had the strongest effect on DM editing and accelerated peptide binding more than 9-fold. Lysine at position α40 is unique to the diabetes associated I-Ag7 molecule and was therefore selected for in vivo evaluation. Homozygous and heterozygous K40E mutant mice showed increased H2-DM protein expression compared to WT littermate controls. Increased H2-DM levels were accompanied by an increase in intra- and extracellular I-Ag7 expression. This suggests that the K40E mutation promotes the interaction between H2-DM and I-Ag7, and likely, represents increased intracellular dimerization and more stable I-Ag7/peptide complexes on the cell surface. Currently, we are evaluating whether increased editing of the MHCII peptide repertoire mediated by the K40E mutation influences spontaneous diabetes development.

Satb2 Ablation Impairs Hippocampus-Based Long-Term Spatial Memory and Short-Term Working Memory and Immediate Early Genes (IEGs)-Mediated Hippocampal Synaptic Plasticity.

Special AT-rich sequence-binding protein 2 (Satb2) is a protein binding to the matrix attachment regions of DNA and important for gene regulation. Patients with SATB2 mutation usually suffer moderate to severe mental retardation. However, the mechanisms for the defects of intellectual activities in patients with SATB2 mutation are largely unclear. Here we established the heterozygous Satb2 mutant mice and Satb2 conditional knockout mice to mimic the patients with SATB2 mutation and figured out the role of Satb2 in mental activities. We found that the spatial memory and working memory were significantly damaged in the heterozygous Satb2 mutant mice, early postnatal Satb2-deficient mice (CaMKIIα-Cre+Satb2fl/fl mice), and adult Satb2 ablation mice (Satb2fl/fl mice injected with CaMKIIα-Cre virus). Functionally, late phase long-term potentiation (L-LTP) in these Satb2 mutant mice was greatly impaired. Morphologically, in CA1 neurons of CaMKIIα-Cre+Satb2fl/fl mice, we found decreased spine density of the basal dendrites and less branches of apical dendrites that extended into lacunar molecular layer. Mechanistically, expression levels of immediate early genes (IEGs) including Fos, FosB, and Egr1 were significantly decreased after Satb2 deletion. And, Satb2 could regulate expression of FosB by binding to the promoter of FosB directly. In general, our study uncovers that Satb2 plays an important role in spatial memory and working memory by regulating IEGs-mediated hippocampal synaptic plasticity.

Amphetamine‐induced Hyperlocomotor Activity in Heterozygous Disc1 Mutant Mice

Disrupted‐in‐Schizophrenia‐1 (DISC1) is a susceptibility gene for several psychiatric illnesses. To study the pathogenesis of these disorders, various Disc1 mutant mouse models were established. In our group, Disc1 mutant mice were generated by introducing the 129S6/SvEv 25‐bp deletion Disc1 variants into the C57BL/6J strain. In this study, a battery of behavioral tests was conducted to evaluate the behavioral phenotypes and cognitive function in the heterozygous Disc1 mutant (Het) mice. In open field test, novel object recognition test, Y‐maze test, and prepulse inhibition test, no significant differences were observed between wildtype (WT) and Het mice. However, after receiving an intraperitoneal injection of amphetamine (5 mg/kg), greater locomotor activity was noticed in Het mice comparing with WT. Moreover, the results of western blot showed lower levels of dopamine transporter (DAT), D1 dopamine receptor (DRD1) and Glycogen synthase kinase 3 (GSK3α/β) and higher level of D2 dopamine receptor (DRD2) in the striatum of Het mice, relative to the WT mice. The dendritic structures of striatal medium spiny neurons were also examined. In the Het mice, reduced dendritic complexity and spine density were noticed. Our results indicated that Disc1 deficit in one allele dose does not alter the basic behavior and cognitive performance in mice. However, lacking one WT Disc1 allele causes the animals to be more vulnerable to the challenge of psychostimulant such as amphetamine, which might be attributed by the altered structure and functions of striatal cells.

Searching for biomarkers of CDKL5 disorder: early-onset visual impairment in CDKL5 mutant mice.

CDKL5 disorder is a neurodevelopmental disorder still without a cure. Murine models of CDKL5 disorder have been recently generated raising the possibility of preclinical testing of treatments. However, unbiased, quantitative biomarkers of high translational value to monitor brain function are still missing. Moreover, the analysis of treatment is hindered by the challenge of repeatedly and non-invasively testing neuronal function. We analyzed the development of visual responses in a mouse model of CDKL5 disorder to introduce visually evoked responses as a quantitative method to assess cortical circuit function. Cortical visual responses were assessed in CDKL5 null male mice, heterozygous females, and their respective control wild-type littermates by repeated transcranial optical imaging from P27 until P32. No difference between wild-type and mutant mice was present at P25-P26 whereas defective responses appeared from P27-P28 both in heterozygous and homozygous CDKL5 mutant mice. These results were confirmed by visually evoked potentials (VEPs) recorded from the visual cortex of a different cohort. The previously imaged mice were also analyzed at P60–80 using VEPs, revealing a persistent reduction of response amplitude, reduced visual acuity and defective contrast function. The level of adult impairment was significantly correlated with the reduction in visual responses observed during development. Support vector machine showed that multi-dimensional visual assessment can be used to automatically classify mutant and wt mice with high reliability. Thus, monitoring visual responses represents a promising biomarker for preclinical and clinical studies on CDKL5 disorder.

CLARITY reveals dynamics of ovarian follicular architecture and vasculature in three-dimensions

Optimal distribution of heterogeneous organelles and cell types within an organ is essential for physiological processes. Unique for the ovary, hormonally regulated folliculogenesis, ovulation, luteal formation/regression and associated vasculature changes lead to tissue remodeling during each reproductive cycle. Using the CLARITY approach and marker immunostaining, we identified individual follicles and corpora lutea in intact ovaries. Monitoring lifetime changes in follicle populations showed age-dependent decreases in total follicles and percentages of advanced follicles. Follicle development from primordial to preovulatory stage was characterized by 3 × 105-fold increases in volume, decreases in roundness, and decreased clustering of same stage follicles. Construction of follicle-vasculature relationship maps indicated age- and gonadotropin-dependent increases in vasculature and branching surrounding follicles. Heterozygous mutant mice with deletion of hypoxia-response element in the vascular endothelial growth factor A (VEGFA) promoter showed defective ovarian vasculature and decreased ovulatory responses. Unilateral intrabursal injection of axitinib, an inhibitor of VEGF receptors, retarded neo-angiogenesis that was associated with defective ovulation in treated ovaries. Our approach uncovers unique features of ovarian architecture and essential roles of vasculature in organizing follicles to allow future studies on normal and diseased human ovaries. Similar approaches could also reveal roles of neo-angiogenesis during embryonic development and tumorigenesis.

SCN3A deficiency associated with increased seizure susceptibility

Mutations in voltage-gated sodium channels expressed highly in the brain (SCN1A, SCN2A, SCN3A, and SCN8A) are responsible for an increasing number of epilepsy syndromes. In particular, mutations in the SCN3A gene, encoding the pore-forming Nav1.3 α subunit, have been identified in patients with focal epilepsy. Biophysical characterization of epilepsy-associated SCN3A variants suggests that both gain- and loss-of-function SCN3A mutations may lead to increased seizure susceptibility. In this report, we identified a novel SCN3A variant (L247P) by whole exome sequencing of a child with focal epilepsy, developmental delay, and autonomic nervous system dysfunction. Voltage clamp analysis showed no detectable sodium current in a heterologous expression system expressing the SCN3A-L247P variant. Furthermore, cell surface biotinylation demonstrated a reduction in the amount of SCN3A-L247P at the cell surface, suggesting the SCN3A-L247P variant is a trafficking-deficient mutant. To further explore the possible clinical consequences of reduced SCN3A activity, we investigated the effect of a hypomorphic Scn3a allele (Scn3aHyp) on seizure susceptibility and behavior using a gene trap mouse line. Heterozygous Scn3a mutant mice (Scn3a+/Hyp) did not exhibit spontaneous seizures nor were they susceptible to hyperthermia-induced seizures. However, they displayed increased susceptibility to electroconvulsive (6Hz) and chemiconvulsive (flurothyl and kainic acid) induced seizures. Scn3a+/Hyp mice also exhibited deficits in locomotor activity and motor learning. Taken together, these results provide evidence that loss-of-function of SCN3A caused by reduced protein expression or deficient trafficking to the plasma membrane may contribute to increased seizure susceptibility.

Neuregulin-1 mutant mice indicate motor and sensory deficits, indeed few references for schizophrenia endophenotype model

Neuregulins (Nrg) are a gene family that binds to tyrosine kinase receptors of the ErbB family. The protein of Nrg1 is to be involved in heart formation, migration of neurons, axonal pathfinding and synaptic function. A relation between Nrg1 and schizophrenia is assumed. Chronic impairment in schizophrenia is characterized by different positive and negative symptoms. Detectable markers of this disease in human and in animal models are activity, social behavior and sensory processing. In this study we compared heterozygous Nrg1 mutant mice in behavior and quantification of dopaminergic and serotoninergic neurons with wild type-like littermates. In the Nrg1 mutant mice the epidermal growth factor-like domain is replaced by the neomycin resistance gene.We found significant differences in locomotor and pain perception behavior. No differences were found in specific schizophrenia social interaction and prepulse inhibition behavior. The number of dopaminergic and serotoninergic neurons did not differ in the investigated regions ventral tegmental area, substantia nigra, periaqueductal grey and raphe nuclei.In conclusion, this analyzed Nrg1 mutant mice model did not serve as a complete schizophrenia model. Particular aspects of schizophrenia disease in locomotor and sensory behavior deficits could represent in this Nrg1 mutant mice. Beside several different models could Nrg1 deficiency represent an endophenotype of schizophrenia disease.

Genetic inhibition of Anaplastic Lymphoma Kinase rescues cognitive impairments in Neurofibromatosis 1 mutant mice

Heterozygous Neurofibromatosis 1 (NF1) loss of function mutations occur in approximately 90% of patients with neurofibromatosis. A major, disabling phenotypic consequence of reduced NF1 function is cognitive impairment; a possibly related behavioral phenotype is impaired sleep. Recent results in Drosophila have demonstrated a genetic interaction between Anaplastic Lymphoma Kinase (Alk) and NF1 for both associative learning and sleep. Inhibition of Alk improves associative learning and sleep in heterozygous NF1 mutant flies. The results in Drosophila provide a strong motivation to investigate NF1/Alk genetic interactions in mice. In Drosophila, activation of Alk by its ligand, Jelly belly (Jeb), is the physiologically relevant target of negative regulation by NF1. Therefore, we tested whether genetic inhibition of Alk in heterozygous NF1 mutant mice attenuates or rescues cognitive impairments in mice. Our results are consistent with the hypothesis that NF1 functions in mice biochemically to inhibit signaling from Alk through Ras. The cognitive phenotypes observed in heterozygous NF1 mutant mice are rescued or ameliorated by genetic inhibition of Alk activity. In two tests of hippocampus-dependent learning, the Morris water maze and extinction of contextual fear, mutation of one or both alleles of Alk was sufficient to improve performance to wild type or near wild type levels in NF1−/+ mice. In addition, in NF1 mice genetic inhibition of Alk improves circadian activity levels. These data are intriguing in light of the circadian alterations seen in NF1 patients and indicate that inhibition of Alk activity may cognitively benefit patients with Neurofibromatosis 1.

Col4a1 mutation generates vascular abnormalities correlated with neuronal damage in a mouse model of HANAC syndrome

The HANAC syndrome is caused by mutations in the gene coding for collagen4a1, a major component of blood vessel basement membranes. Ocular symptoms include an increase in blood vessel tortuosity and occasional hemorrhages. To examine how vascular defects can affect neuronal function, we analyzed the retinal phenotype of a HANAC mouse model. Heterozygous mutant mice displayed both a thinning of the basement membrane in retinal blood vessels and in Bruch's membrane resulting in vascular leakage. Homozygous mice had additional vascular changes, including greater vessel coverage and tortuosity. This greater tortuosity was associated to higher expression levels of vascular endothelial growth factor (VEGF). These major changes to the blood vessels were correlated with photoreceptor dysfunction and degeneration. The neuronal damage was associated with reactive gliosis in astrocytes and Müller glial cells, and by the migration of microglial cells into the outer retina. This study illustrates how vascular changes can trigger neuronal degeneration in a new model of HANAC syndrome that can be used to further study dysfunctions of neurovascular coupling. Summary statementThis study provides a phenotypic analysis of a novel mouse model of HANAC syndrome focusing on the retinal aspect. It recapitulates most of the aspects of the human disease and is therefore a great tool to study and to address this condition.

A mouse model for inherited renal fibrosis associated with endoplasmic reticulum stress.

ABSTRACTRenal fibrosis is a common feature of renal failure resulting from multiple etiologies, including diabetic nephropathy, hypertension and inherited renal disorders. However, the mechanisms of renal fibrosis are incompletely understood and we therefore explored these by establishing a mouse model for a renal tubular disorder, referred to as autosomal dominant tubulointerstitial kidney disease (ADTKD) due to missense uromodulin (UMOD) mutations (ADTKD-UMOD). ADTKD-UMOD, which is associated with retention of mutant uromodulin in the endoplasmic reticulum (ER) of renal thick ascending limb cells, is characterized by hyperuricemia, interstitial fibrosis, inflammation and renal failure, and we used targeted homologous recombination to generate a knock-in mouse model with an ADTKD-causing missense cysteine to arginine uromodulin mutation (C125R). Heterozygous and homozygous mutant mice developed reduced uric acid excretion, renal fibrosis, immune cell infiltration and progressive renal failure, with decreased maturation and excretion of uromodulin, due to its retention in the ER. The ER stress marker 78 kDa glucose-regulated protein (GRP78) was elevated in cells expressing mutant uromodulin in heterozygous and homozygous mutant mice, and this was accompanied, both in vivo and ex vivo, by upregulation of two unfolded protein response pathways in primary thick ascending limb cells from homozygous mutant mice. However, this did not lead to an increase in apoptosis in vivo. Thus, we have developed a novel mouse model for renal fibrosis, which will be a valuable resource to decipher the mechanisms linking uromodulin mutations with ER stress and renal fibrosis.