title: The expression and function of the achaete-scute genes in Tribolium castaneum reveals conservation and variation in neural pattern formation and cell fate specification.
abstract: The study of achaete-scute (ac/sc) genes has recently become a paradigm to understand the evolution and development of the arthropod nervous system. We describe the identification and characterization of the ac/sc genes in the coleopteran insect species Tribolium castaneum. We have identified two Tribolium ac/sc genes - achaete-scute homolog (Tc-ASH) a proneural gene and asense (Tc-ase) a neural precursor gene that reside in a gene complex. Focusing on the embryonic central nervous system we find that Tc-ASH is expressed in all neural precursors and the proneural clusters from which they segregate. Through RNAi and misexpression studies we show that Tc-ASH is necessary for neural precursor formation in Tribolium and sufficient for neural precursor formation in Drosophila. Comparison of the function of the Drosophila and Tribolium proneural ac/sc genes suggests that in the Drosophila lineage these genes have maintained their ancestral function in neural precursor formation and have acquired a new role in the fate specification of individual neural precursors. Furthermore, we find that Tc-ase is expressed in all neural precursors suggesting an important and conserved role for asense genes in insect nervous system development. Our analysis of the Tribolium ac/sc genes indicates significant plasticity in gene number, expression and function, and implicates these modifications in the evolution of arthropod neural development.
authors.affiliation: Program in Neuroscience, Washington University School of Medicine, St. Louis, MO 63110, USA.
authors.forename: Scott R
authors.initials: SR
authors.lastname: Wheeler
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Carrico
authors.forename: Beth A
authors.initials: BA
authors.lastname: Wilson
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Brown
authors.forename: James B
authors.initials: JB
authors.lastname: Skeath
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D001921:Brain / Q000166:cytology / Q000254:growth & development / Q000502:physiology; D019070:Cell Lineage; D004268:DNA-Binding Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D017344:Genes, Insect; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D009024:Morphogenesis; D010802:Phylogeny; D016415:Sequence Alignment; D014157:Transcription Factors / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D014231:Tribolium / Q000196:embryology* / Q000235:genetics* / Q000502:physiology
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D014157:Transcription Factors; C089199:ac protein, Drosophila; C089197:sc protein, Drosophila