Project description:Fish and Chips: Expression Profiling in Non-traditional Model Systems Using a Cichlid Fish cDNA Microarray This series represents the 26 arrays that went into Renn et al 2004 (submitted January 16th), and one additional hybridization (GSM15240) that was not included in the publication analysis for statistical reasons.
Project description:Fish and Chips: Expression Profiling in Non-traditional Model Systems Using a Cichlid Fish cDNA Microarray This series represents the 26 arrays that went into Renn et al 2004 (submitted January 16th), and one additional hybridization (GSM15240) that was not included in the publication analysis for statistical reasons. Keywords: other
2004-02-05 | GSE975 | GEO
Project description:Comparative gene expression in fin tissue of a cichlid fish
Project description:East African cichlid fishes have radiated in an explosive fashion. The (epi)genetic basis for the abundant phenotypic diversity of these fishes remains largely unknown. As transposable elements (TEs) contribute extensively to genome evolution, we reasoned that TEs may have fuelled cichlid radiations. While TE-derived genetic and epigenetic variability has been associated with phenotypic traits, TE expression and epigenetic silencing remain unexplored in cichlids. Here, we profiled TE expression in African cichlids, and describe dynamic expression patterns during embryogenesis and according to sex. Most TE silencing factors are conserved and expressed in cichlids. We describe an expansion of two truncated Piwil1 genes in Lake Malawi/Nyasa cichlids, encoding a Piwi domain with catalytic potential. To further dissect epigenetic silencing of TEs, we focused on small RNA-driven epigenetic silencing. We detect a small RNA population in gonads consistent with an active Piwi-interacting RNA (piRNA) pathway targeting TEs. We uncover fluid genomic origins of piRNAs in closely related cichlid species. This, along with signatures of positive selection in piRNA pathway factors, points towards fast co-evolution of TEs and the piRNA pathway. Our study is the first step to understand the contribution of ongoing TE-host arms races to the cichlid radiations in Africa.
Project description:East African cichlid fishes have diversified in an explosive fashion, but the (epi)genetic basis of the phenotypic diversity of these fishes remains largely unknown. Although transposable elements (TEs) have been associated with phenotypic variation in cichlids, little is known about their transcriptional activity and epigenetic silencing. Here, we describe dynamic patterns of TE expression in African cichlid gonads and during early development. Orthology inference revealed an expansion of piwil1 genes in Lake Malawi cichlids, likely driven by PiggyBac TEs. The expanded piwil1 copies have signatures of positive selection and retain amino acid residues essential for catalytic activity. Furthermore, the gonads of African cichlids express a Piwi-interacting RNA (piRNA) pathway that target TEs. We define the genomic sites of piRNA production in African cichlids and find divergence in closely related species, in line with fast evolution of piRNA-producing loci. Our findings suggest dynamic co-evolution of TEs and host silencing pathways in the African cichlid radiations. We propose that this co-evolution has contributed to cichlid genomic diversity.
Project description:Most behaviors are associated with heritable genetic variation. Genetic mapping has revealed genomic regions or, in a few cases, specific genes explaining part of this variation. However, understanding how genetic divergence shapes behavioral evolution remains unclear. Here we analyze the evolution of an innate extended phenotype: bower building among male cichlid fish of Lake Malawi, which build bowers of two types, pits and castles. F1 hybrids of pit-digging and castle-building species perform sequential construction of first pit and then castle bowers. Analysis of brain gene expression in these hybrids showed that genes near behavior-associated variants display behavior-dependent allele-specific expression with preferential expression of the pit-species allele during pit digging, and of the castle-species allele during castle building. These genes are highly enriched for functions and pathways involved in neurodevelopment and neural plasticity. Our results suggest that natural behaviors can be associated with complex genetic architectures that alter behavior via cis-regulatory differences whose effects on gene expression are specific to the behavior itself.
Project description:Throughout the animal kingdom, we know many examples of mating system evolution that exemplify adaptive responses to changes in the environment, yet our understanding of the accompanying neural and molecular mechanisms that give rise to such behavioral changes remains understudied. In the present study we aimed to define the molecular basis of interspecific variation in social organization in Ectodini cichlids from Lake Tanganyika. We selected four closely related species that represent two independent evolutions of monogamy: the polygynous Xenotilapia ochrogenys, the monogamous Xenotilapia flavipinnis, the polygynous Microdontochromis tenuidentata and the monogamous Asprotilapia leptura. Using a single cichlid microarray platform, we conducted a total of 28 direct comparisons for neural gene expression level among males and 26 among females of four species that represent 2 independent evolutions of monogamy. Our results indicate the gene expression profiles display remarkable plasticity across different time scales because we find differences associated with sex, mating system, and lineage.
Project description:Inheritance and plasticity of epigenetic divergence characterise early stages of speciation in an incipient cichlid species of an African crater lake.
Project description:Evolutionary alterations to cis-regulatory sequences are likely to cause adaptive phenotypic complexity, through orchestrating changes in cellular proliferation, identity and communication. For non-model organisms with adaptive key-innovations, patterns of regulatory evolution have been predominantly limited to targeted sequence-based analyses. Chromatin-immunoprecipitation with high-throughput sequencing (ChIP-seq) is a technology that has only been used in genetic model systems and is a powerful experimental tool to screen for active cis-regulatory elements. Here, we show that it can also be used in ecological model systems and permits genome-wide functional exploration of cis-regulatory elements. As a proof of concept, we use ChIP-seq technology in adult fin tissue of the cichlid fish Oreochromis niloticus to map active promoter elements, as indicated by occupancy of trimethylated Histone H3 Lysine 4 (H3K4me3). The fact that cichlids are one of the most phenotypically diverse and species-rich families of vertebrates could make them a perfect model system for the further in-depth analysis of the evolution of transcriptional regulation. examination of H3K4me3 in adult fin tissue of the Nile tilapia (Oreochromis niloticus)