title: Engrailed-2 (En2) deletion produces multiple neurodevelopmental defects in monoamine systems, forebrain structures and neurogenesis and behavior.
abstract: Many genes involved in brain development have been associated with human neurodevelopmental disorders, but underlying pathophysiological mechanisms remain undefined. Human genetic and mouse behavioral analyses suggest that ENGRAILED-2 (EN2) contributes to neurodevelopmental disorders, especially autism spectrum disorder. In mouse, En2 exhibits dynamic spatiotemporal expression in embryonic mid-hindbrain regions where monoamine neurons emerge. Considering their importance in neuropsychiatric disorders, we characterized monoamine systems in relation to forebrain neurogenesis in En2-knockout (En2-KO) mice. Transmitter levels of serotonin, dopamine and norepinephrine (NE) were dysregulated from Postnatal day 7 (P7) to P21 in En2-KO, though NE exhibited the greatest abnormalities. While NE levels were reduced ∼35% in forebrain, they were increased 40 -: 75% in hindbrain and cerebellum, and these patterns paralleled changes in locus coeruleus (LC) fiber innervation, respectively. Although En2 promoter was active in Embryonic day 14.5 -: 15.5 LC neurons, expression diminished thereafter and gene deletion did not alter brainstem NE neuron numbers. Significantly, in parallel with reduced NE levels, En2-KO forebrain regions exhibited reduced growth, particularly hippocampus, where P21 dentate gyrus granule neurons were decreased 16%, suggesting abnormal neurogenesis. Indeed, hippocampal neurogenic regions showed increased cell death (+77%) and unexpectedly, increased proliferation. Excess proliferation was restricted to early Sox2/Tbr2 progenitors whereas increased apoptosis occurred in differentiating (Dcx) neuroblasts, accompanied by reduced newborn neuron survival. Abnormal neurogenesis may reflect NE deficits because intra-hippocampal injections of β-adrenergic agonists reversed cell death. These studies suggest that disruption of hindbrain patterning genes can alter monoamine system development and thereby produce forebrain defects that are relevant to human neurodevelopmental disorders.
authors.affiliation: Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, Rutgers.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Genestine
authors.affiliation: Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, Rutgers, Graduate School of Biological Sciences, Rutgers.
authors.forename: Lulu
authors.initials: L
authors.lastname: Lin
authors.affiliation: Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, Rutgers, Graduate School of Biological Sciences, Rutgers.
authors.forename: Madel
authors.initials: M
authors.lastname: Durens
authors.affiliation: Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, Rutgers, Graduate School of Biological Sciences, Rutgers.
authors.forename: Yan
authors.initials: Y
authors.lastname: Yan
authors.affiliation: Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, Rutgers.
authors.forename: Yiqin
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, Rutgers.
authors.forename: Smrithi
authors.initials: S
authors.lastname: Prem
authors.affiliation: Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
authors.forename: Kunal
authors.initials: K
authors.lastname: Bailoor
authors.affiliation: Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Kelly
authors.affiliation: Department of Neurology, Rutgers Robert Wood Johnson Medical School, Rutgers.
authors.forename: Patricia K
authors.initials: PK
authors.lastname: Sonsalla
authors.affiliation: Center for Advanced Biotechnology and Medicine, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Matteson
authors.affiliation: MIND Institute, University of California Davis School of Medicine, Sacramento, CA, USA.
authors.forename: Jill
authors.initials: J
authors.lastname: Silverman
authors.affiliation: MIND Institute, University of California Davis School of Medicine, Sacramento, CA, USA.
authors.forename: Jacqueline N
authors.initials: JN
authors.lastname: Crawley
authors.affiliation: Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, Rutgers, Center for Advanced Biotechnology and Medicine, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
authors.forename: James H
authors.initials: JH
authors.lastname: Millonig
authors.affiliation: Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, Rutgers, Graduate School of Biological Sciences, Rutgers, Department of Pediatrics, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, New Brunswick, NJ, USA and diciccem@rwjms.rutgers.edu.
authors.forename: Emanuel
authors.initials: E
authors.lastname: DiCicco-Bloom
mesh_terms: D000818:Animals; D059290:Dopaminergic Neurons / Q000378:metabolism* / Q000502:physiology; D000089662:Doublecortin Protein; D005260:Female; D017353:Gene Deletion; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000235:genetics*; D055495:Neurogenesis; D009638:Norepinephrine / Q000378:metabolism; D016548:Prosencephalon / Q000254:growth & development / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D059326:Serotonergic Neurons / Q000378:metabolism* / Q000502:physiology; D013550:Swimming; D000099266:Engrailed 2 Protein
chemical_list: D000089662:Doublecortin Protein; D018398:Homeodomain Proteins; D009419:Nerve Tissue Proteins; D009638:Norepinephrine; D000099266:Engrailed 2 Protein; C000714847:Dcx protein, mouse