Browsing by Author "Scharff, C"

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    For whom the bird sings: context-dependent gene expression.
    (Neuron, 1998-10) Jarvis, ED; Scharff, C; Grossman, MR; Ramos, JA; Nottebohm, F
    Male zebra finches display two song behaviors: directed and undirected singing. The two differ little in the vocalizations produced but greatly in how song is delivered. "Directed" song is usually accompanied by a courtship dance and is addressed almost exclusively to females. "Undirected" song is not accompanied by the dance and is produced when the male is in the presence of other males, alone, or outside a nest occupied by its mate. Here, we show that the anterior forebrain vocal pathway contains medial and lateral "cortical-basal ganglia" subdivisions that have differential ZENK gene activation depending on whether the bird sings female-directed or undirected song. Differences also occur in the vocal output nucleus, RA. Thus, although these two vocal behaviors are very similar, their brain activation patterns are dramatically different.
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    Selective expression of insulin-like growth factor II in the songbird brain.
    (J Neurosci, 1997-09-15) Holzenberger, M; Jarvis, ED; Chong, C; Grossman, M; Nottebohm, F; Scharff, C
    Neuronal replacement occurs in the forebrain of juvenile and adult songbirds. To address the molecular processes that govern this replacement, we cloned the zebra finch insulin-like growth factor II (IGF-II) cDNA, a factor known to regulate neuronal development and survival in other systems, and examined its expression pattern by in situ hybridization and immunocytochemistry in juvenile and adult songbird brains. The highest levels of IGF-II mRNA expression occurred in three nuclei of the song system: in the high vocal center (HVC), in the medial magnocellular nucleus of the neostriatum (mMAN), which projects to HVC, and to a lesser extent in the robust nucleus of the archistriatum (RA), which receives projections from HVC. IGF-II mRNA expression was developmentally regulated in zebra finches. In canary HVC, monthly changes in IGF-II mRNA expression covaried with previously reported monthly differences in neuron incorporation. Combining retrograde tracers with in situ hybridization and immunocytochemistry, we determined that the HVC neurons that project to area X synthesize the IGF-II mRNA, whereas the adjacent RA-projecting neurons accumulate the IGF-II peptide. Our findings raise the possibility that within HVC IGF-II acts as a paracrine signal between nonreplaceable area X-projecting neurons and replaceable RA-projecting neurons, a mode of action that is compatible with the involvement of IGF-II with the replacement of neurons. Additional roles for IGF-II expression in songbird brain are likely, because expression also occurs in some brain areas outside the song system, among them the cerebellar Purkinje cells in which neurogenesis is not known to occur.
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    Site-specific retinoic acid production in the brain of adult songbirds.
    (Neuron, 2000-08) Denisenko-Nehrbass, NI; Jarvis, E; Scharff, C; Nottebohm, F; Mello, CV
    The song system of songbirds, a set of brain nuclei necessary for song learning and production, has distinctive morphological and functional properties. Utilizing differential display, we searched for molecular components involved in song system regulation. We identified a cDNA (zRalDH) that encodes a class 1 aldehyde dehydrogenase. zRalDH was highly expressed in various song nuclei and synthesized retinoic acid efficiently. Brain areas expressing zRalDH generated retinoic acid. Within song nucleus HVC, only projection neurons not undergoing adult neurogenesis expressed zRalDH. Blocking zRalDH activity in the HVC of juveniles interfered with normal song development. Our results provide conclusive evidence for localized retinoic acid synthesis in an adult vertebrate brain and indicate that the retinoic acid-generating system plays a significant role in the maturation of a learned behavior.