Abstract
BackgroundLake 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.ResultsWe 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.ConclusionsOn 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.
Highlights
Lake Malawi cichlids represent one of a growing number of vertebrate models used to uncover the genetic and developmental basis of trait diversity
Bone morphogenetic protein and transforming growth factor beta pathway The transforming growth factor beta (TGF-β) superfamily is a class of cytokines organized into Transforming growth factor (TGF)-βs, bone morphogenetic proteins (BMPs), and activin/inhibins that bind
All of the BMP pathway factors we include are expressed in the jaw once it has formed in the larval stage, and many are expressed in the pharynx, as indicated in Table 1. bmp2 and bmp4 pattern, generate, shape, and regenerate teeth in mice, squamates, and cichlids [29,30,31,32,33,34,35]
Summary
Lake Malawi cichlids represent one of a growing number of vertebrate models used to uncover the genetic and developmental basis of trait diversity. Comparative gene expression is a hallmark of the evolution and development research program [1]. This is the case among closely related vertebrate species, like hominids [2], beach mice [3], cavefishes [4], stickleback [5], and cichlid fishes [6]. In these examples and many others, diversity in key traits evolves via spatial, temporal and/or quantitative variation in gene expression. Despite the importance of changes in gene expression to the evolution of closely related species, comprehensive surveys of spatial expression patterns are typically confined to laboratory models (e.g., zebrafish, [7]).
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