title: Onset of Tlx-3 expression in the chick cerebellar cortex correlates with the morphological development of fissures and delineates a posterior transverse boundary.
abstract: Recent studies have shown that the mammalian cerebellar cortex can be subdivided into a reproducible array of zones and stripes. In particular, discontinuous patterns of gene expression together with mutational analysis suggest that there are at least four distinct transverse zones along the rostrocaudal axis in mouse: the anterior zone (lobules I-V), the central zone (lobules VI and VII), the posterior zone (lobules VIII and IX), and the nodular zone (lobule X). Here we show that the divergent homeobox-containing transcription factor, Tlx- 3 (also known as Hox11L2 or Rnx) is transiently expressed in external granule cells in a distinct transverse domain of the developing chick cerebellar cortex. Expression is first detected at Hamburger and Hamilton (HH) stage 35. Interestingly, Tlx-3 mRNA expression is initially confined to, and coincident with, the morphological development of fissures. Slightly later, at HH stage 38, expression extends throughout the developing external granular layer (EGL) of lobules I-IXab. Notably, no Tlx-3 expression was detected in lobules IXc and X at any developmental time point examined. Expression is noticeably stronger in nonproliferating cells located in the deep layer of the EGL. Tlx-3 expression is downregulated as granule cells migrate inward to form the internal granule layer and is undetectable shortly after birth. These results suggest that Tlx-3 is expressed as granule cells become postmitotic and suggest that Tlx-3 may play a role in the differentiation of distinct neuronal populations in the cerebellum.
authors.affiliation: Genes and Development Research Group, Department of Cell Biology and Anatomy, Faculty of Medicine, University of Calgary, Calgary AB T2N 4N1, Canada. clogan@ucalgary.ca
authors.forename: Cairine
authors.initials: C
authors.lastname: Logan
authors.forename: Cassie
authors.initials: C
authors.lastname: Millar
authors.forename: Vinay
authors.initials: V
authors.lastname: Bharadia
authors.forename: Katherine
authors.initials: K
authors.lastname: Rouleau
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000235:genetics*; D002454:Cell Differentiation / Q000235:genetics*; D002525:Cerebellar Cortex / Q000166:cytology / Q000196:embryology* / Q000378:metabolism*; D002642:Chick Embryo / Q000166:cytology / Q000196:embryology* / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D006609:High Mobility Group Proteins / Q000235:genetics / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics*; D008938:Mitosis / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D015513:Oncogene Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D055751:SOXC Transcription Factors; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism
chemical_list: D006609:High Mobility Group Proteins; D018398:Homeodomain Proteins; D015513:Oncogene Proteins; D012333:RNA, Messenger; D055751:SOXC Transcription Factors; C490793:Sox11 protein, mouse; C487378:Tlx1 protein, mouse