@article {32, title = {Normalization of RNA-sequencing data from samples with varying mRNA levels.}, journal = {PLoS One}, volume = {9}, year = {2014}, month = {2014}, pages = {e89158}, abstract = {

Methods for normalization of RNA-sequencing gene expression data commonly assume equal total expression between compared samples. In contrast, scenarios of global gene expression shifts are many and increasing. Here we compare the performance of three normalization methods when polyA(+) RNA content fluctuates significantly during zebrafish early developmental stages. As a benchmark we have used reverse transcription-quantitative PCR. The results show that reads per kilobase per million (RPKM) and trimmed mean of M-values (TMM) normalization systematically leads to biased gene expression estimates. Biological scaling normalization (BSN), designed to handle differences in total expression, showed improved accuracy compared to the two other methods in estimating transcript level dynamics. The results have implications for past and future studies using RNA-sequencing on samples with different levels of total or polyA(+) RNA.

}, keywords = {Animals, Base Sequence, Gene Expression, Gene Expression Profiling, Polymerase Chain Reaction, RNA, Messenger, Sequence Analysis, RNA, Zebrafish}, issn = {1932-6203}, doi = {10.1371/journal.pone.0089158}, author = {Aanes, H{\r a}vard and Winata, Cecilia L and Moen, Lars F and {\O}strup, Olga and Mathavan, Sinnakaruppan and Collas, Philippe and Rognes, Torbj{\o}rn and Alestr{\"o}m, Peter} } @article {34, title = {Prepatterning of developmental gene expression by modified histones before zygotic genome activation.}, journal = {Dev Cell}, volume = {21}, year = {2011}, month = {2011 Dec 13}, pages = {993-1004}, abstract = {

A hallmark of anamniote vertebrate development is a window of embryonic transcription-independent cell divisions before onset of zygotic genome activation (ZGA). Chromatin determinants of ZGA are unexplored; however, marking of developmental genes by modified histones in sperm suggests a predictive role of histone marks for ZGA. In zebrafish, pre-ZGA development for ten cell cycles provides an opportunity to examine whether genomic enrichment in modified histones is present before initiation of transcription. By profiling histone H3 trimethylation on all zebrafish promoters before and after ZGA, we demonstrate here an epigenetic prepatterning of developmental gene expression. This involves pre-ZGA marking of transcriptionally inactive genes involved in homeostatic and developmental regulation by permissive H3K4me3 with or without repressive H3K9me3 or H3K27me3. Our data suggest that histone modifications are instructive for the developmental gene expression program.

}, keywords = {Animals, Body Patterning, Chromatin, Epigenesis, Genetic, Female, Gene Expression Regulation, Developmental, Histones, Male, Methylation, Multigene Family, Promoter Regions, Genetic, Spermatozoa, Zebrafish, Zebrafish Proteins}, issn = {1878-1551}, doi = {10.1016/j.devcel.2011.10.008}, author = {Lindeman, Leif C and Andersen, Ingrid S and Reiner, Andrew H and Li, Nan and Aanes, H{\r a}vard and {\O}strup, Olga and Winata, Cecilia L and Mathavan, Sinnakaruppan and M{\"u}ller, Ferenc and Alestr{\"o}m, Peter and Collas, Philippe} } @article {36, title = {Zebrafish mRNA sequencing deciphers novelties in transcriptome dynamics during maternal to zygotic transition.}, journal = {Genome Res}, volume = {21}, year = {2011}, month = {2011 Aug}, pages = {1328-38}, abstract = {

Maternally deposited mRNAs direct early development before the initiation of zygotic transcription during mid-blastula transition (MBT). To study mechanisms regulating this developmental event in zebrafish, we applied mRNA deep sequencing technology and generated comprehensive information and valuable resources on transcriptome dynamics during early embryonic (egg to early gastrulation) stages. Genome-wide transcriptome analysis documented at least 8000 maternal genes and identified the earliest cohort of zygotic transcripts. We determined expression levels of maternal and zygotic transcripts with the highest resolution possible using mRNA-seq and clustered them based on their expression pattern. We unravel delayed polyadenylation in a large cohort of maternal transcripts prior to the MBT for the first time in zebrafish. Blocking polyadenylation of these transcripts confirms their role in regulating development from the MBT onward. Our study also identified a large number of novel transcribed regions in annotated and unannotated regions of the genome, which will facilitate reannotation of the zebrafish genome. We also identified splice variants with an estimated frequency of 50\%-60\%. Taken together, our data constitute a useful genomic information and valuable transcriptome resource for gene discovery and for understanding the mechanisms of early embryogenesis in zebrafish.

}, keywords = {Animals, Base Sequence, Genome, RNA, Messenger, RNA, Messenger, Stored, Sequence Analysis, RNA, Transcriptome, Zebrafish, Zebrafish Proteins, Zygote}, issn = {1549-5469}, doi = {10.1101/gr.116012.110}, author = {Aanes, H{\r a}vard and Winata, Cecilia L and Lin, Chi Ho and Chen, Jieqi P and Srinivasan, Kandhadayar G and Lee, Serene G P and Lim, Adrian Y M and Hajan, Hajira Shreen and Collas, Philippe and Bourque, Guillaume and Gong, Zhiyuan and Korzh, Vladimir and Alestr{\"o}m, Peter and Mathavan, Sinnakaruppan} } @article {69, title = {Chromatin states of developmentally-regulated genes revealed by DNA and histone methylation patterns in zebrafish embryos.}, journal = {Int J Dev Biol}, volume = {54}, year = {2010}, month = {2010}, pages = {803-13}, abstract = {

Embryo development proceeds from a cascade of gene activation and repression events controlled by epigenetic modifications of DNA and histones. Little is known about epigenetic states in the developing zebrafish, despite its importance as a model organism. We report here DNA methylation and histone modification profiles of promoters of developmentally-regulated genes (pou5f1, sox2, sox3, klf4, nnr, otx1b, nes, vasa), as well as tert and bactin2, in zebrafish embryos at the mid-late blastula transition, shortly after embryonic genome activation. We identify four classes of promoters based on the following profiles: (i) those enriched in marks of active genes (H3K9ac, H4ac, H3K4me3) without transcriptionally repressing H3K9me3 or H3K27me3; (ii) those enriched in H3K9ac, H4ac and H3K27me3, without H3K9me3; one such gene was klf4, shown by in situ hybridization to be mosaically expressed, likely accounting for the detection of both activating and repressive marks on its promoter; (iii) those enriched in H3K4me3 and H3K27me3 without acetylation; and (iv) those enriched in all histone modifications examined. Culture of embryo-derived cells under differentiation conditions leads to H3K9 and H4 deacetylation and H3K9 and H3K27 trimethylation on genes that are inactivated, yielding an epigenetic profile similar to those of fibroblasts or muscle. All promoters however retain H3K4me3, indicating an uncoupling of H3K4me3 occupancy and gene expression. All non-CpG island developmentally-regulated promoters are DNA unmethylated in embryos, but hypermethylated in fibroblasts. Our results suggest that differentially expressed embryonic genes are regulated by various patterns of histone modifications on unmethylated DNA, which create a developmentally permissive chromatin state.

}, keywords = {Animals, Blastula, Cell Line, Chromatin, Chromatin Immunoprecipitation, CpG Islands, DNA Methylation, Embryo, Nonmammalian, Fibroblasts, Gene Expression Profiling, Gene Expression Regulation, Developmental, Histones, In Situ Hybridization, Lysine, Methylation, Oligonucleotide Array Sequence Analysis, Promoter Regions, Genetic, Reverse Transcriptase Polymerase Chain Reaction, Zebrafish, Zebrafish Proteins}, issn = {1696-3547}, doi = {10.1387/ijdb.103081ll}, author = {Lindeman, Leif C and Winata, Cecilia L and Aanes, Hvard and Mathavan, Sinnakaruppan and Alestrom, Peter and Collas, Philippe} }