title: Developmental restriction of the LIM homeodomain transcription factor Islet-1 expression to cholinergic neurons in the rat striatum.
abstract: LIM homeodomain transcription factors play crucial roles in determining diverse aspects of neuronal development both in vertebrates and invertebrates. In the present study, we studied the expression pattern of Islet-1 (Isl-1), a member of the LIM homeodomain protein family, in the rat striatum during development. The developmental expression of Isl-1 in the striatum is highly dynamic and complex in terms of spatial and temporal regulation. The reverse transcription-polymerase chain reaction and ribonuclease protection assays demonstrated that Isl-1 messenger RNA was expressed in the developing striatum. The immunocytochemical study of Isl-1 protein expression showed that there were prominent mediolateral and caudorostral Isl-1 gradients in the developing striatum. Numerous Isl-1-positive cells appeared in the medial mantle zone of the developing striatal proper, and they co-expressed the postmitotic neuronal marker, microtubule-associated protein 2. The numbers of Isl-1-positive cells were decreased from the medial to the lateral regions, so that there were only a few Isl-1-positive cells scattered in the lateral striatum. These scattered Isl-1-positive cells were doubly labeled with tyrosine kinase receptor A and choline acetyltransferase, which indicated that they were cholinergic neurons. The Isl-1 gradients were most prominent in the embryonic day 18 and 20 striatum. With increases of time, the Isl-1 gradients were gradually reduced, and the gradients disappeared by postnatal day 7. Despite the general down-regulation of striatal Isl-1, a few Isl-1-positive cells were sustained into the adult striatum in which Isl-1 was nearly exclusively expressed by all cholinergic neurons and vice versa. Our study suggests that Isl-1 is likely to be initially expressed by postmitotic cholinergic precursors and some, if not all, non-cholinergic precursors in the developing striatum. During the progression of striatal differentiation, Isl-1 is down-regulated in non-cholinergic cells, but is sustained in cholinergic cells. The developmental restriction of Isl-1 to cholinergic neurons in the striatum may represent a novel mechanism by which LIM homeodomain proteins specify specific cell types in the striatum during development.
authors: Institute of Neuroscience, National Yang-Ming University, Taipei, 112, Republic of, Taiwan, China.
authors: H F
authors: HF
authors: Wang
authors: F C
authors: FC
authors: Liu
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology; D015415:Biomarkers; D002454:Cell Differentiation; D002795:Choline O-Acetyltransferase / Q000378:metabolism*; D003342:Corpus Striatum / Q000166:cytology / Q000196:embryology* / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000502:physiology; D005314:Embryonic and Fetal Development; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D066298:In Vitro Techniques; D060850:LIM-Homeodomain Proteins; D009419:Nerve Tissue Proteins; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D016548:Prosencephalon / Q000196:embryology / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020917:Receptor, trkA / Q000378:metabolism; D014157:Transcription Factors
chemical_list: D015415:Biomarkers; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; C063843:insulin gene enhancer binding protein Isl-1; D002795:Choline O-Acetyltransferase; D020917:Receptor, trkA