Gene expression in developing rat hippocampal pyramidal neurons appears independent of mossy fiber innervation.
In the rat, neonatal gamma-irradiation of the hippocampus induces a selective destruction of dentate granule cells and prevents the development of the mossy fiber-CA3 pyramidal cell connection. In the absence of mossy fiber input, the CA3 pyramidal neurons exhibit morphological alterations and rats deprived of dentate granule cells fail to develop kainate-induced epileptic activity in the CA3 pyramidal neurons. Neonatal elimination of the granule cells also impairs learning and memory tasks in adult rats. In the present work, we assessed by in situ hybridization and semi-quantitative RT-PCR, whether in the pyramidal layers, the absence of mossy fiber input alters the expression of a number of genes involved in activity-dependent signal transduction, in GABAergic neurotransmitter signaling and in neurite development via microtubule organization. Surprisingly, we show that the expression and the developmentally regulated alternative splicing of the genes we examined in the developing hippocampus are not altered in the pyramidal neurons, whether the dentate granule afferents are present or absent. Our results suggest that in the CA3 pyramidal layer, the developmental expression patterns of the mRNAs we studied are independent of extrinsic cues provided by mossy fiber input.
Collet
J
J
Université René Descartes, Paris V, INSERM Unité 29, France.
Pollard
H
H
Moreau
J
J
Diabira
D
D
Ben
A Y
AY
Khrestchatisky
M
M
D017398:Alternative Splicing; D000818:Animals; D000831:Animals, Newborn; D001483:Base Sequence; D003598:Cytoskeletal Proteins / Q000235:genetics; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics; D051766:Early Growth Response Protein 1; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D017874:Immediate-Early Proteins; D017403:In Situ Hybridization; D008297:Male; D019599:Mossy Fibers, Hippocampal / Q000000981:diagnostic imaging / Q000502:physiology*; D017966:Pyramidal Cells / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics; D011859:Radiography; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics
D003598:Cytoskeletal Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; D012333:RNA, Messenger; D011963:Receptors, GABA-A; D014157:Transcription Factors