title: Down-regulation of 14-3-3 eta gene expression by IGF-I in mouse cerebellum during postnatal development.
abstract: Insulin-like growth factor I (IGF-I) overexpression in the postnatal cerebellum of transgenic (Tg) mice results in remarkable cerebellar overgrowth characterized by a near doubling of granule cell number that is predominantly due to inhibition of apoptosis. Using this Tg model we set out to investigate IGF-I anti-apoptotic mechanisms by defining the influence of IGF-I on gene expression. Using a cDNA array technique, we screened a total of 243 mouse apoptosis-related genes, and found that 14-3-3 eta gene expression was significantly reduced in the cerebella of Tg mice compared with their wild-type (Wt) littermates. Using Northern blot analysis to corroborate our microarray finding, we showed that 14-3-3 eta mRNA abundance was decreased from postnatal day P5 through P17. Nonetheless, the expression pattern of 14-3-3 eta in Tg mice followed the same pattern observed in Wt mice, and was indistinguishable from that in Wt mice at P20 and P23. 14-3-3 eta protein abundance, as determined by Western immunoblot analyses, showed similar decreases in the cerebella of Tg mice. In situ hybridization demonstrated that 14-3-3 eta was predominantly, if not exclusively, expressed and regulated in Purkinje cells. 14-3-3 proteins have multiple functions, including participation in pathways that favor cell survival. Our finding of IGF-I-induced down-regulation of 14-3-3 eta expression in Purkinje cell at a time when IGF-I promotes granule cell survival leads us to speculate that down-regulation of 14-3-3 eta may: (a) serve a negative feedback role to modulate Purkinje cell survival, i.e. limit Purkinje cell number, and/or (b) function as part of a distinct signaling mechanism, perhaps one that augments the capacity of Purkinje cells to promote granule cell survival.
authors.affiliation: Department of Pediatrics, Division of Endocrinology, CB# 7039, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7039, USA.
authors.forename: Jihui
authors.initials: J
authors.lastname: Zhang
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Popken
authors.forename: Ping
authors.initials: P
authors.lastname: Ye
authors.forename: A Joseph
authors.initials: AJ
authors.lastname: D'Ercole
mesh_terms: D048948:14-3-3 Proteins; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000235:genetics; D015152:Blotting, Northern; D015153:Blotting, Western; D002531:Cerebellum / Q000254:growth & development* / Q000378:metabolism; D015536:Down-Regulation; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D017403:In Situ Hybridization; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D020411:Oligonucleotide Array Sequence Analysis; D011689:Purkinje Cells / Q000166:cytology / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D014446:Tyrosine 3-Monooxygenase / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D048948:14-3-3 Proteins; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D014446:Tyrosine 3-Monooxygenase