RESUMO
BACKGROUND: Lake Malawi cichlids represent one of a growing number of vertebrate models used to uncover the genetic and developmental basis of trait diversity. Rapid evolutionary radiation has resulted in species that share similar genomes but differ markedly in phenotypes including brains and behavior, nuptial coloration and the craniofacial skeleton. Research has begun to identify the genes, as well as the molecular and developmental pathways that underlie trait divergence. RESULTS: We assemble a compendium of gene expression for Lake Malawi cichlids, across pharyngula (the phylotypic stage) and larval stages of development, encompassing hundreds of gene transcripts. We chart patterns of expression in Bone morphogenetic protein (BMP), Fibroblast growth factor (FGF), Hedgehog (Hh), Notch and Wingless (Wnt) signaling pathways, as well as genes involved in neurogenesis, calcium and endocrine signaling, stem cell biology, and numerous homeobox (Hox) factors-in three planes using whole-mount in situ hybridization. Because of low sequence divergence across the Malawi cichlid assemblage, the probes we employ are broadly applicable in hundreds of species. We tabulate gene expression across general tissue domains, and highlight examples of unexpected expression patterns. CONCLUSIONS: On the heels of recently published genomes, this compendium of developmental gene expression in Lake Malawi cichlids provides a valuable resource for those interested in the relationship between evolution and development.
Assuntos
Ciclídeos/genética , Proteínas de Peixes/genética , Regulação da Expressão Gênica no Desenvolvimento , Genes Controladores do Desenvolvimento/genética , Animais , Ciclídeos/crescimento & desenvolvimento , Evolução Molecular , Modelos Animais , FenótipoRESUMO
Receptor gated Ca2+ entry has been associated with transient receptor potential (TRP) proteins encoded by several different genes. Here, we compare expression of mRNA for TRP isoforms encoded by genes TRP1-6 in the rat substantia nigra and whole brain. The substantia nigra and the whole brain expressed mRNA predominantly for TRP3 and TRP6. The levels of TRP1, 2, 4 and 5 were very low in both. The TRP6 mRNA levels in substantia nigra and the whole brain were comparable while those for TRP3 were significantly lower in substantia nigra than in the whole brain. Thus substantia nigra differs from the whole brain in its TRP expression.
Assuntos
Canais de Cálcio/genética , Sinalização do Cálcio/fisiologia , Expressão Gênica/fisiologia , Neurônios/metabolismo , Substância Negra/metabolismo , Animais , Masculino , Neurônios/citologia , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Substância Negra/citologia , Canais de Cátion TRPCRESUMO
The telencephalon is the most complex brain region, controlling communication, emotion, movement and memory. Its adult derivatives develop from the dorsal pallium and ventral subpallium. Despite knowledge of genes required in these territories, we do not understand how evolution has shaped telencephalon diversity. Here, using rock- and sand-dwelling cichlid fishes from Lake Malawi, we demonstrate that differences in strength and timing of opposing Hedgehog and Wingless signals establish evolutionary divergence in dorsal-ventral telencephalon patterning. Rock dwellers exhibit early, extensive Hedgehog activity in the ventral forebrain resulting in expression of foxg1 before dorsal Wingless signals, and a larger subpallium. Sand dwellers show rapid deployment of Wingless, later foxg1 expression and a larger pallium. Manipulation of the Hedgehog and Wingless pathways in cichlid and zebrafish embryos is sufficient to mimic differences between rock- versus sand-dweller brains. Our data suggest that competing ventral Hedgehog and dorsal Wingless signals mediate evolutionary diversification of the telencephalon.