ABSTRACT
In utero ethanol exposure from a mother's consumption of alcoholic beverages impacts brain and cognitive development, creating a range of deficits in the child (Levitt, 1998; Lebel et al., 2012). Children diagnosed with fetal alcohol spectrum disorders (FASD) are often born with facial dysmorphology and may exhibit cognitive, behavioral, and motor deficits from ethanol-related neurobiological damage in early development. Prenatal ethanol exposure (PrEE) is the number one cause of preventable mental and intellectual dysfunction globally, therefore the neurobiological underpinnings warrant systematic research. We document novel anatomical and gene expression abnormalities in the neocortex of newborn mice exposed to ethanol in utero. This is the first study to demonstrate large-scale changes in intraneocortical connections and disruption of normal patterns of neocortical gene expression in any prenatal ethanol exposure animal model. Neuroanatomical defects and abnormal neocortical RZRß, Id2, and Cadherin8 expression patterns are observed in PrEE newborns, and abnormal behavior is present in 20-d-old PrEE mice. The vast network of neocortical connections is responsible for high-level sensory and motor processing as well as complex cognitive thought and behavior in humans. Disruptions to this network from PrEE-related changes in gene expression may underlie some of the cognitive-behavioral phenotypes observed in children with FASD.
Subject(s)
Behavior, Animal/drug effects , Cerebral Cortex/metabolism , Fetal Alcohol Spectrum Disorders/physiopathology , Fetal Alcohol Spectrum Disorders/psychology , Gene Expression/drug effects , Prenatal Exposure Delayed Effects/physiopathology , Prenatal Exposure Delayed Effects/psychology , Animals , Cadherins/biosynthesis , Cadherins/genetics , Cell Count , Cerebral Cortex/drug effects , Cerebral Cortex/pathology , Ethanol/blood , Female , Fetal Alcohol Spectrum Disorders/genetics , In Vitro Techniques , Inhibitor of Differentiation Protein 2/biosynthesis , Inhibitor of Differentiation Protein 2/genetics , Mice , Microscopy, Fluorescence , Nuclear Receptor Subfamily 1, Group F, Member 2/biosynthesis , Nuclear Receptor Subfamily 1, Group F, Member 2/genetics , Osmolar Concentration , Pregnancy , Pregnancy, Animal/drug effects , Prenatal Exposure Delayed Effects/genetics , Weight GainABSTRACT
A hallmark of mammalian evolution is the structural and functional complexity of the cerebral cortex. Within the cerebral cortex, the neocortex, or isocortex, is a 6-layered complexly organized structure that is comprised of multiple interconnected sensory and motor areas. These areas and their precise patterns of connections arise during development, through a process termed arealization. Intrinsic, activity-independent and extrinsic, activity-dependent mechanisms are involved in the development of neocortical areas and their connections. The intrinsic molecular mechanisms involved in the establishment of this sophisticated network are not fully understood. In this report (I) and the companion report (II), we present the first lifespan analysis of ipsilateral intraneocortical connections (INCs) among multiple sensory and motor regions, from the embryonic period to adulthood in the mouse. Additionally, we characterize the neocortical expression patterns of several developmentally regulated genes that are of central importance to studies investigating the molecular control of arealization from embryonic day 13.5 to postnatal day (P) 3 (I) and P6 to 50 (II). In this analysis, we utilize novel methods to correlate the boundaries of gene expression with INCs and developing areal boundaries, in order to better understand the nature of gene-areal relationships during development.
Subject(s)
Cerebral Cortex/embryology , Cerebral Cortex/growth & development , Gene Expression Regulation, Developmental/physiology , Gene Expression/physiology , Age Factors , Amino Acids/metabolism , Animals , Animals, Newborn , Brain Mapping , COUP Transcription Factors/genetics , COUP Transcription Factors/metabolism , Cadherins/genetics , Cadherins/metabolism , Cerebral Cortex/cytology , Embryo, Mammalian , Ephrin-A5/genetics , Ephrin-A5/metabolism , Female , Homeodomain Proteins/genetics , Homeodomain Proteins/metabolism , Inhibitor of Differentiation Protein 2/genetics , Inhibitor of Differentiation Protein 2/metabolism , LIM-Homeodomain Proteins , Mice , Neural Pathways/embryology , Neural Pathways/growth & development , Neural Pathways/metabolism , Nuclear Receptor Subfamily 1, Group F, Member 2/genetics , Nuclear Receptor Subfamily 1, Group F, Member 2/metabolism , Pregnancy , Pyridinium Compounds/metabolism , Receptor, EphA7/genetics , Receptor, EphA7/metabolism , Transcription Factors/genetics , Transcription Factors/metabolismABSTRACT
The mammalian neocortex contains an intricate processing network of multiple sensory and motor areas that allows the animal to engage in complex behaviors. These anatomically and functionally unique areas and their distinct connections arise during early development, through a process termed arealization. Both intrinsic, activity-independent and extrinsic, activity-dependent mechanisms drive arealization, much of which occurs during the areal patterning period (APP) from late embryogenesis to early postnatal life. How areal boundaries and their connections develop and change from infancy to adulthood is not known. Additionally, the adult patterns of sensory and motor ipsilateral intraneocortical connections (INCs) have not been thoroughly characterized in the mouse. In this report and its companion (I), we present the first lifespan analysis of ipsilateral INCs among multiple sensory and motor regions in mouse. We describe the neocortical expression patterns of several developmentally regulated genes that are of central importance to studies investigating the molecular regulation of arealization, from postnatal day (P) 6 to P50. In this study, we correlate the boundaries of gene expression patterns with developing areal boundaries across a lifespan, in order to better understand the nature of gene-areal relationships from early postnatal life to adulthood.
Subject(s)
Brain Mapping , Cerebral Cortex/growth & development , Gene Expression Regulation, Developmental/physiology , Gene Expression/physiology , Neural Pathways/growth & development , Age Factors , Amino Acids/metabolism , Animals , Animals, Newborn , COUP Transcription Factors/genetics , COUP Transcription Factors/metabolism , Cadherins/genetics , Cadherins/metabolism , Cerebral Cortex/cytology , Embryo, Mammalian , Ephrin-A5/genetics , Ephrin-A5/metabolism , Female , Functional Laterality , Homeodomain Proteins/genetics , Homeodomain Proteins/metabolism , Inhibitor of Differentiation Protein 2/genetics , Inhibitor of Differentiation Protein 2/metabolism , LIM-Homeodomain Proteins , Mice , Neural Pathways/metabolism , Nuclear Receptor Subfamily 1, Group F, Member 2/genetics , Nuclear Receptor Subfamily 1, Group F, Member 2/metabolism , Pregnancy , Pyridinium Compounds/metabolism , Receptor, EphA7/genetics , Receptor, EphA7/metabolism , Transcription Factors/genetics , Transcription Factors/metabolismABSTRACT
Ecdysis, or the shedding of the old cuticle, depends on coordinated stereotyped behaviors, regulated by a number of neuropeptides. In the hornworm, Manduca sexta, two neuropeptides interact, namely ecdysis-triggering hormone (ETH) and eclosion hormone. We looked at the effects of ETH in vivo and in vitro, on the brain and the ventral nerve cord to determine the roles played by these hormones. We monitored ecdysis onset and the presence of cGMP and eclosion hormone immunoreactivity. In vivo, only a fraction of larvae lacking the cell bodies containing eclosion hormone, and injected with ETH, were able to undergo ecdysis, with a delayed response. These animals showed strongest cGMP immunoreactivity in the subesophageal and thoracic ganglia, with concomitant reductions in eclosion hormone immunoreactivity in descending axons in comparison with animals not undergoing ecdysis. Animals lacking the brain showed reduced to no cGMP levels in all ganglia. In vitro, isolated CNS preparations lacking the brain initiated ecdysis motor programs after incubation in ETH, with faster onset times than controls, and with reduced cGMP immunoreactivity. If ETH was applied only to the brain of the isolated CNS, cGMP immunoreactivity was noted primarily in the subesophageal and thoracic ganglia, with a decrease in eclosion hormone immunoreactivity in descending axons. ETH addition to the rest of the nerve cord showed reduced eclosion hormone immunoreactivity but little to no cGMP immunoreactivity in any ganglion. Controls showed strong cGMP immunoreactivity in all ganglia, and even greater reductions in eclosion hormone staining after ETH application. These results support previous suggestions that eclosion hormone is required for a positive feedback loop with ETH as well as onset of an inhibitory component, but also suggest that ETH stimulates eclosion hormone release at multiple spike initiation zones. The resultant up regulation of cGMP does not appear to be required for onset of ecdysis. A new model for ecdysis regulation is considered.
