Sars Internal Seminars 2007/2008
Sars Seminar Room (222 A2) at 13:00

Date Speaker Title and Abstract
12.oct Holger Bielen
Technau Group
Tracing the evolution of the mesoderm - characterisation of Brachyury paralogs in a diploblastic animal, the cnidarian Hydra.
17.oct Sutada Mungpakdee
Chourrout Group
Duplication and evolutionary rate of Hox genes in Atlantic salmon.
Hox cluster organisation represents a valuable marker to study the effects of recent genome duplication in salmonid fish (25-100 million years ago). Using PCR amplification of cDNAs, BAC library screening and genome walking, we reconstructed 13 Hox clusters containing 118 Hox genes including 8 pseudogenes in the Atlantic salmon. Salmon seems to lack one HoxAb and both HoxDb clusters. Hox paralogs that originate from the duplication predating the radiation of ray-finned fish have been better preserved in salmon than in other model teleosts. Most gene loss and pseudogenisation in the salmon lineage have occurred after the 4R genome duplication. Recent duplicates of salmon Hox genes have diverged relatively fast and often asymmetrically, although their rate of evolution strongly varied depending on the individual Hox cluster. Hox gene evolution after the last duplication was driven by differential meiotic behavior of duplicated chromosomes and purifying selection after a relaxation of selective constraints, but the effect of positive selection could not be detected. Gene expression analysis by RNA-RNA in situ hybridisation supports the duplication-degeneration-complementation (DDC) model in which subfunctionalisation preferentially affects cis-regulatory elements and favors the retention of recently duplicated genes.
24.oct Fabian Rentzsch
Technau Group
FGF signalling controls formation of the apical sensory organ in the cnidarian Nematostella vectensis.
Fibroblast Growth Factor (FGF) signaling regulates essential developmental processes in vertebrates and invertebrates but its role during early metazoan evolution remains obscure. Here we analyze the function of two paralogous FGFs (NvFGFa and NvFGFb), and one FGF receptor (NvFGFRa) of the sea anemone Nematostella that are expressed in the developing apical organ, a sensory structure located at the aboral pole of ciliated larvae from various phyla. Morpholino-mediated knockdown experiments reveal that NvFGFa and NvFGFRa are required for the formation of the apical organ, whereas NvFGFb counteracts NvFGFRa signaling to prevent precocious and ectopic apical organ development. Marker gene expression analysis shows that FGF signaling regulates local patterning in the aboral region. Furthermore, NvFGFa activates its own expression and that of the antagonistic NvFGFb, thereby establishing positive and negative feedback loops. Finally we show that loss of the apical organ upon NvFGFa knockdown blocks metamorphosis into polyps. We propose that the control of the development of sensory structures at the apical pole of ciliated larvae is an ancestral function of FGF signaling.
31.oct Anna Zofia Komisarczuk
Becker Group
cis-regulation and mis-regulation of fgf8 in zebrafish.
07.nov Michael Saina
Technau Group
Investigating the roles of TGF-ß signaling in the basal metazoan Nematostella vectensis
Dpp/BMP4 plays crucial roles in the establishment of the dorso-ventral body axis in bilaterians. Cnidarians are the sister group to the Bilateria and therefore of considerable importance for the understanding of the evolution of axial properties. Here we analyze by morpholino knockdown the roles of dpp/bmp5-8 and chordin. In the starlet sea anemone Nematostella vectensis.
14.nov Rita Angotzi
Chourrout Group
Fish pituitary genes during development and evolution.
Several transcription regulators play key roles during pituitary morphogenesis, including the K50 paired-like homeodomain proteins. Here we report the characterization of the Pitx-gene complements in zebrafish and salmon with special emphasis on Pitx-expression patterns during pituitary development. Comparative studies of zebrafish, salmon and mouse indicate both conservation and divergence of spatial expression domains between mammals and fish Pitx orthologs. In particular, our study suggests that the Pitx gene complement of each species preserves conservation of ancestral pituitary expression during morphogenesis through complementary shuffling of expression between the distinct Pitx members of the family. Moreover, our analysis on the Pitx salmon repertoire, suggests a rapid evolution of the family in this species, as differential loss of spatial domains and differences in expression time and levels are observed between duplicates. These processes may have been engaged in the last 25-100 million years of recent salmonids evolution. Depletion of the paired-like Prop1 gene in mouse causes severe pituitary hypoplasia with failure of the entire Pit1 lineage. We have examined whether antisense morpholino oligonucleotides can be used as a tool to suppress or "knockdown" the expression of Prop1 during development of the zebrafish pituitary gland. Possible implications on pituitary morphology and down-stream effects on expression of Pit1 gene will be discussed.
21.nov Pavla Navratilova
Becker Group
Regulatory activity of vertebrate highly conserved non-coding elements in zebrafish
28.nov Jens Fritzenwanker
Technau Group
Early development, axis specification and apical organ formation in the sea anemone Nematostella vectensis
12.dec Grigory Genikhovich
Technau Group
Differential expression of Mef2 splice variants in Nematostella vectensis.

Christmas Break

16.jan Patrick Steinmetz
Technau Group
The evolution of muscles and mesoderm in Metazoa.
23.jan Yoshimasa Sagane
Thompson Group
Cellulose and chitin based structure in Appendicularian urochordate Oikopleura dioica.
30.jan Alexandra Schulmeister
Thompson Group
“High diversity of histone variants in the larvacean, Oikopleura dioica: Mass spectrometric analysis and developmental specific expression.”
The basic structural matrix of chromosomes, chromatin, involves complex interactions between DNA and proteins. Many nuclear functions are carried out on the heart of chromatin structure, the nucleosome, consisting of 147 bp DNA wrapped around an octameric unit of small disc-shaped proteins, the histones H2A, H2B, H3 and H4 which mediate the folding of DNA into chromatin. Linker histone H1 binds DNA close to the nucleosomal dyad axis and further stabilizes the chromatin fiber. Through histone posttranslational modifications (PTMs) and ATP-dependant chromatin remodeling the accessibility of nucleosomal DNA to nuclear machinery is positively and negatively modulated.

Histone variants alter the composition of individual nucleosomes and expand the PTM repertoire. With the exception of histone H4, several different variants of each histone subtype have been reported for most organisms. The Oikopleura histone complement comprises 47 genes encoding 37 different variants, a number exceeding the library of variants known in mammals and other organisms. Sequence comparison to human histone variants revealed that most mammalian variants are also present in the Oikopleura complement. Performing quantitative RT-PCR on several developmental stages we have assessed the expression profile for all variants throughout Oikopleura development. Spermatogenesis in many organisms, requires incorporation of histone variants that precede subsequent histone removal and replacement by protamines. To test whether this is also the case in Oikopleura, male and female specific samples were included in the analysis and 14 male specific variants identified. Further, we have begun to determine the nuclear localization of the Oikopleura H3 variant family members with EGFP fusion constructs. Many studies examining histone modifications have concluded that the combination of modifications on nucleosomes may be the key to determining chromatin structure and function in a variety of organisms. There is evidence, however, that some histone modifications and their dynamics may have different interpretations and roles across divergent evolutionary groups of organisms. In collaboration with the Nijmegen Centre for Molecular Life Sciences and the Proteomic Unit in Bergen, we have begun to analyse Oikopleura histones by mass spectrometry and identified several conserved histone modifications. We are planning to further extend this data to compare different histone modification patterns on the variants and to identify variant specific PMTs.
06.feb Satoko Awazu
Jiang Group
Transposon-mediated transgenesis in the ascidian Ciona intestinalis .
13.feb tba tba
20.feb Øyvind Drivenes
Becker Group
Regulation of microRNA expression by highly conserved non-coding elements (HCNEs).
27.feb tba
05.mar Fekadu Yadetie
Chourrout Group
“Nuclear Receptors and their expression in Oikopleura dioica.”
12.mar tba

Easter Break

02.apr Silke Rinkwitz
Becker Group
“A genomic screen reveals principles of developmental gene regulation and genome architecture.”
09.apr Marcin Adamski
To be rescheduled
16.apr Beena Punnamoottil
Becker Group
Expression of the Hox4 paralogous genes in zebrafish - an insight into neuronal subtypes and gene regulation.
23.apr Julia Hosp
Thompson Group
Molecular Scaffolding of the Oikopleura house.
30.apr Puja Gupta
Becker Group
07.may tba tba
14.may 07.may tba tba
21.may Jan Christian Bryne
Lenhard Group
Finding key elements of proximal promoters by studying TBP mutants.
28.may David Fredman
Lenhard Group
Cis-regulatory mutation in cancer

Sars Abstracts - 2006 - 2009/2010