title: Monoamine oxidase a expression is vital for embryonic brain development by modulating developmental apoptosis.
abstract: Monoamine oxidases (MAO-A, MAO-B) metabolize biogenic amines and have been implicated in neuronal apoptosis. Although apoptosis is an important process in embryo development, the role of MAO isoenzymes has not been investigated in detail. We found that expression of MAO-A and MAO-B can be detected early on during embryo development. Expression levels remained constant until around midgestation but then dropped to almost undetectable levels toward birth. Similar expression kinetics were observed in the brain. Isoform-specific expression silencing of MAO-A mediated by siRNA during in vitro embryogenesis induced developmental defects, as indicated by a reduction of the crown rump length and impaired cerebral development. These alterations were paralleled by elevated serotonin levels. Similar abnormalities were observed when embryos were cultured in the presence of the MAO-A inhibitor clorgyline or when the transcriptional inhibitor of MAO-A expression R1 was overexpressed. In contrast, no such alterations were detected when expression of MAO-B was knocked down. To explore the underlying mechanisms for the developmental abnormalities in MAO-A knockdown embryos, we quantified the degree of developmental apoptosis in the developing brain. MAO-A knockdown reduced the number of apoptotic cells in the neuroepithelium, which coincided with impaired activation of caspases 3 and 9. Moreover, we observed reduced cyclin D1 levels as an indicator of impaired cell proliferation in MAO-A knockdown embryos. This data highlights MAO-A as a vital regulator of embryonic brain development.
authors.affiliation: Institute of Biochemistry, University Medicine Berlin-Charité, Oudenarder Strasse 16, 13347 Berlin, Germany.
authors.forename: Chi Chiu
authors.initials: CC
authors.lastname: Wang
authors.forename: Astrid
authors.initials: A
authors.lastname: Borchert
authors.forename: Aslihan
authors.initials: A
authors.lastname: Ugun-Klusek
authors.forename: Ling Yin
authors.initials: LY
authors.lastname: Tang
authors.forename: Wai Ting
authors.initials: WT
authors.lastname: Lui
authors.forename: Ching Yan
authors.initials: CY
authors.lastname: Chu
authors.forename: Ellen
authors.initials: E
authors.lastname: Billett
authors.forename: Hartmut
authors.initials: H
authors.lastname: Kuhn
authors.forename: Christoph
authors.initials: C
authors.lastname: Ufer
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001921:Brain / Q000166:cytology / Q000196:embryology / Q000201:enzymology; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D053453:Caspase 9 / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D003010:Clorgyline / Q000494:pharmacology; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology / Q000196:embryology / Q000201:enzymology; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology*; D055785:Gene Knockdown Techniques; D051379:Mice; D008995:Monoamine Oxidase / Q000096:biosynthesis* / Q000235:genetics; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: C530105:Ccnd1 protein, mouse; D008996:Monoamine Oxidase Inhibitors; D034741:RNA, Small Interfering; D019938:Cyclin D1; D008995:Monoamine Oxidase; C505409:Casp3 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053453:Caspase 9; D003010:Clorgyline