title: CNS midline cells contribute to maintenance of the initial dorsoventral patterning of the Drosophila ventral neuroectoderm.
abstract: Dorsoventral patterning of the Drosophila ventral neuroectoderm is established by the expression of three evolutionarily conserved homeodomain genes: ventral nervous system defective (vnd), intermediate neuroblasts defective (ind), and muscle segment homeobox (msh) in the medial, intermediate, and lateral columns of the ventral neuroectoderm, respectively. It was not clear whether extrinsic factor(s) from the CNS midline cells influence the initial dorsoventral patterning by controlling the expression of the dorsoventral patterning genes. We show here that the CNS midline cells, specified by single-minded (sim), are essential for maintaining expression of the dorsoventral patterning genes. Ectopic expression of sim in the ventral neuroectoderm during the blastoderm stage repressed expression of the three homeodomain genes in the ventral neuroectoderm. This indicates that the identity of the CNS midline cells is established by a series of repressions of the three homeodomain genes in the ventral neuroectoderm. Ectopic expression of sim in the ventral neuroectoderm during initial neurogenesis induced ectopic ind expression in the medial column in addition to that in the intermediate column via EGFR signaling between the ventral neuroectoderm and midline cells. In contrast, it repressed the expression of vnd and msh in the medial and lateral columns, respectively. Our findings demonstrate that the CNS midline cells provide extrinsic positional information via EGFR signaling that maintains the initial subdivision of the ventral neuroectoderm into three dorsoventral columns during initial neurogenesis.
authors.affiliation: Department of Chemistry, Konkuk University, Seoul 143-701, Korea.
authors.forename: In Ok
authors.initials: IO
authors.lastname: Kim
authors.forename: In Chul
authors.initials: IC
authors.lastname: Kim
authors.forename: Sunmi
authors.initials: S
authors.lastname: Kim
authors.forename: Yeon Kyung
authors.initials: YK
authors.lastname: Kwon
authors.forename: Pyung-Lim
authors.initials: PL
authors.lastname: Han
authors.forename: Sang-Hak
authors.initials: SH
authors.lastname: Jeon
authors.forename: Sang Hee
authors.initials: SH
authors.lastname: Kim
mesh_terms: D000818:Animals; D002490:Central Nervous System / Q000166:cytology* / Q000196:embryology / Q000378:metabolism; D004330:Drosophila / Q000166:cytology* / Q000196:embryology / Q000378:metabolism; D029721:Drosophila Proteins / Q000096:biosynthesis; D004475:Ectoderm / Q000166:cytology* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology
chemical_list: D029721:Drosophila Proteins