Lower NPAS3 expression during the later stages of abnormal lung development in rat congenital diaphragmatic hernia

Purpose Congenital diaphragmatic hernia (CDH) is characterized by a developmental defect in the diaphragm, pulmonary hypoplasia and pulmonary hypertension. NPAS3 is a PAS domain transcription factor regulating Drosophila tracheogenesis. NPAS3 null mice develop pulmonary hypoplasia in utero and die after birth due to respiratory failure. We aimed to evaluate NPAS3 expres- sion during normal and abnormal lung development due to CDH. Methods CDH was induced by administering 100 mg/ml nitrofen to time-pregnant dams on embryonic day (E) 9 of gestation. Lungs were isolated on E15, E18 and E21 and NPAS3 localization was determined by immunohisto- chemistry and quantified using Western blotting. Results We found that only E21 hypoplastic CDH lungs have reduced expression of NPAS3 in the terminal sac- cules. Western blotting confirmed the down-regulation of NPAS3 protein in the nitrofen-induced hypoplastic lungs. Conclusions We demonstrate for the first time that ni- trofen-induced hypoplastic CDH lungs have reduced NPAS3 expression in the terminal saccules during the later stages of abnormal lung development. Our findings suggest that NPAS3 is associated with pulmonary hypoplasia in CDH.Supported by the Children’s Hospital Research Institute of Manitoba; RK is the recipient of a Career Enhancement Award from the Canadian Child Health Clinician Scientist Program and a New Investigator Salary Award from the Canadian Institutes of Health Research, Manitoba Lung Association and the Children’s Hospital Research Institute

Genetic Labeling of Neuronal Subsets through Enhancer Trapping in Mice

The ability to label, visualize, and manipulate subsets of neurons is critical for elucidating the structure and function of individual cell types in the brain. Enhancer trapping has proved extremely useful for the genetic manipulation of selective cell types in Drosophila. We have developed an enhancer trap strategy in mammals by generating transgenic mice with lentiviral vectors carrying single-copy enhancer-detector probes encoding either the marker gene lacZ or Cre recombinase. This transgenic strategy allowed us to genetically identify a wide variety of neuronal subpopulations in distinct brain regions. Enhancer detection by lentiviral transgenesis could thus provide a complementary method for generating transgenic mouse libraries for the genetic labeling and manipulation of neuronal subsets

Besides Purkinje cells and granule neurons: an appraisal of the cell biology of the interneurons of the cerebellar cortex

n/

NPAS1 Represses the Generation of Specific Subtypes of Cortical Interneurons

SummaryLittle is known about genetic mechanisms that regulate the ratio of cortical excitatory and inhibitory neurons. We show that NPAS1 and NPAS3 transcription factors (TFs) are expressed in progenitor domains of the mouse basal ganglia (subpallium, MGE, and CGE). NPAS1−/− mutants had increased proliferation, ERK signaling, and expression of Arx in the MGE and CGE. NPAS1−/− mutants also had increased neocortical inhibition (sIPSC and mIPSC) and generated an excess of somatostatin+ (SST) (MGE-derived) and vasoactive intestinal polypeptide+ (VIP) (CGE-derived) neocortical interneurons, but had a normal density of parvalbumin+ (PV) (MGE-derived) interneurons. In contrast, NPAS3−/− mutants showed decreased proliferation and ERK signaling in progenitors of the ganglionic eminences and had fewer SST+ and VIP+ interneurons. NPAS1 repressed activity of an Arx enhancer, and Arx overexpression resulted in increased proliferation of CGE progenitors. These results provide insights into genetic regulation of cortical interneuron numbers and cortical inhibitory tone

Interacting haplotypes at the NPAS3 locus alter risk of schizophrenia and bipolar disorder

The neuronal PAS domain 3 (NPAS3) gene encodes a neuronal transcription factor that is implicated in psychiatric disorders by the identification of a human chromosomal translocation associated with schizophrenia and a mouse knockout model with behavioural and hippocampal neurogenesis defects. To determine its contribution to the risk of psychiatric illness in the general population, we genotyped 70 single-nucleotide polymorphisms across the NPAS3 gene in 368 individuals with bipolar disorder, 386 individuals with schizophrenia and 455 controls. Modestly significant single-marker and global and individual haplotypes were identified in four discrete regions of the gene. The presence of both risk and protective haplotypes at each of these four regions indicated locus and allelic heterogeneity within NPAS3 and suggested a model whereby interactions between variants across the gene might contribute to susceptibility to illness. This was supported by predicting the most likely haplotype for each individual at each associated region and then calculating an NPAS3-mediated 'net genetic load' value. This value differed significantly from controls for both bipolar disorder (P = 0.0000010) and schizophrenia (P = 0.0000012). Logistic regression analysis also confirmed the combinatorial action of the four associated regions on disease risk. In addition, sensitivity/specificity plots showed that the extremes of the genetic loading distribution possess the greatest predictive power-a feature suggesting multiplicative allele interaction. These data add to recent evidence that the combinatorial analysis of a number of relatively small effect size haplotypes may have significant power to predict an individual's risk of a complex genetic disorder such as psychiatric illness

Chromosome abnormalities, mental retardation and the search for genes in bipolar disorder and schizophrenia

Genetic factors contribute to schizophrenia and bipolar disorder, and linkage and association studies have been successful in identifying several candidate genes. However these genes explain only a very small part of the total population risk and the psychoses appear to be very heterogeneous with several models of genetic inheritance relevant to different groups of patients, including some cases caused by multiple common genetic variants, while others are single gene disorders. Studying chromosomal abnormalities is a useful strategy for identifying genes in illness, and patients with both mental retardation and psychosis form a special group where large chromosomal abnormalities detected by routine cytogenetic analysis are more prevalent than in patients with schizophrenia or bipolar disorder alone, or in the general population. Studying these patients provides valuable opportunities to identify genes contributing to psychoses. This review of the literature on large chromosomal rearrangements in patients with mental retardation and psychotic illness illustrates how schizophrenia and bipolar phenotypes are associated with a large number of different chromosomal disruptions. Recent genome wide association studies have identified an excess of small chromosomal deletions and duplications in schizophrenia, adding further support to the importance of chromosomal structural variation in psychotic illness. The genes GRIK4 and NPAS3, each associated with psychosis in patients with mental retardation are discussed to illustrate the value of rare cytogenetic events as a means to signpost neurobiological pathways of general importance for illness in the wider population