title: Novel connection between newborn granule neurons and the hippocampal CA2 field.
abstract: Newborn neurons are continuously added to the hippocampal dentate gyrus (DG) throughout life. Mature and immature granule neurons are believed to send their axonal projections exclusively to the hippocampal CA3 field. However, recent data point to an alternative trisynaptic circuit, involving a direct axonal projection from mature granule neurons to the CA2 field. Whether this circuit takes place only in mature granule neurons or, on the contrary, whether immature granule neurons also contribute to this novel connection is unknown. We used various retroviral vectors to show that immature granule neurons send axonal processes to and establish synaptic contacts with CA2 pyramidal neurons and that axonal growth follows a similar time course to that described for CA3 innervation. In addition, we provide experimental evidence demonstrating that the pathway connecting newborn granule neurons and the CA2 field can be modulated by physiological and deleterious stimuli.
authors.affiliation: Centro de Biología Molecular Severo Ochoa (CSIC-UAM), c/Nicolás Cabrera 1, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED, ISCIII), c/Valderrebollo 5, Madrid, Spain. Electronic address: m.llorens@csic.es.
authors.forename: María
authors.initials: M
authors.lastname: Llorens-Martín
authors.affiliation: Centro de Biología Molecular Severo Ochoa (CSIC-UAM), c/Nicolás Cabrera 1, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED, ISCIII), c/Valderrebollo 5, Madrid, Spain.
authors.forename: Jerónimo
authors.initials: J
authors.lastname: Jurado-Arjona
authors.affiliation: Centro de Biología Molecular Severo Ochoa (CSIC-UAM), c/Nicolás Cabrera 1, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED, ISCIII), c/Valderrebollo 5, Madrid, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Avila
authors.affiliation: Centro de Biología Molecular Severo Ochoa (CSIC-UAM), c/Nicolás Cabrera 1, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED, ISCIII), c/Valderrebollo 5, Madrid, Spain. Electronic address: fhernandez@cbm.uam.es.
authors.forename: Félix
authors.initials: F
authors.lastname: Hernández
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D056651:CA2 Region, Hippocampal / Q000166:cytology* / Q000254:growth & development*; D005260:Female; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D009434:Neural Pathways / Q000166:cytology / Q000254:growth & development*; D055495:Neurogenesis / Q000502:physiology*; D009474:Neurons / Q000166:cytology*
keywords: Adult neurogenesis; CA2; Granule neurons; Mossy fiber terminal; Retrovirus