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CHAIR OF DEVELOPMENTAL BIOCHEMISTRY
Hey function in adult angiogenesis
Mouse retina to make angiogensis defects visible.
Mouse retina

One developmental aspect of our lab is the study of the role of Hey1/2 and Hes1 transcription factors during angiogenesis. Therefore, we use the so called retina model, which allows to study angiogenesis in vivo. Via staining of endothelia cells it is possible to make angiogensis defects visible.

Hey function in endothelia cell differentiation
Hey1/2 deficient mouse embryonic stem cells
Hey1/2 deficient mouse embryonic stem cells
Endothelia cells derived from Hey1/2 deficient mouse embryonic stem cells after 14 days of differentiation
Endothelia cells derived from Hey1/2 deficient mouse embryonic stem cells after 14 days of differentiation

We are using mouse embryonic stem cells to differentiate them into endothelial cells. Through comparative analysis between normal, Hey deficient and Hey inducible cells we want to investigate the role of Hey genes in angiogenic cell fate determination and to reveal differences in the arterio-venous differentiation of endothelial cells. Therefore we are using functional assays to investigate proliferation and sprouting as well as RNA-Seq and qRT-PCR to identify downstream target genes of Hey.

Identification of Hey interaction partners
SDS-PAGE silver staining shows Hey1 tandem purification
Hey1 tandem purification

Although distinct Hey1 dimerization partners have been identified so far, there are still open questions concerning the molecular mechanism how Hey1 function is influenced by these factors. Furthermore, we are interested in posttranslational modifications of Hey1 proteins and their impact on Hey1 function. To gain a closer insight into Hey1 biochemical function and behavior we sought to identify new Hey1 associated proteins as well as distinct posttranslational modifications using the tandem affinity purification approach and mass spectrometry (MS) analysis in collaboration with the mass spectrometry of the Max-Planck-Institute Göttingen and the Rudolf-Virchow-Center Würzburg.

Identification of novel Hey target genes
Hey ChIPseq profile in UCSC genome browser
Hey ChIPseq profile in UCSC genome browser

We use chromatin immunoprecipitation and microarrays to identify novel Hey target genes. Previous experiments in HEK293 cells have identified Hey proteins as highly redundant repressors. Target genes are mainly other transcription factors involved in various developmental processes. As another system we use murine embryonic stem cells, which can be efficiently differentiated into other cell types (e.g. cardiomyocytes, endothelia cells). We use this system to identify target genes which are especilly relevant for the cardio-vascular defects observed in Hey knockout mice

Hey backgroundinformationen
Hey activation by notch signallingHey activation by notch signalling
Hey activation by notch signallingHey activation by notch signalling
Relationship between different Hey proteins
Relationship between different Hey proteins

Hey genes (Hey1, Hey2 and HeyL) encode hairy-related bHLH transcription factors that are direct targets of the Notch signaling pathway (Maier, 2000). The proteins can form dimers with other bHLH factors and they function as transcriptional repressors.

Hey expression
Hey1, Hey2 and HeyL expression during mouse embryo development
Hey1, Hey2 and HeyL expression during mouse embryo development

During mouse development Hey genes are dynamically expressed in various processes like somitogenesis, neurogenesis, nephrogenesis and cardiovascular development (Leimeister, 1999, 2000).

We have generated knockout mouse lines for all three Hey genes
Ventricle septum defect in HeyL/1 double KO
Ventricle septum defect in HeyL/1 double KO

Loss of Hey2 results in a dramatic developmental defect of the heart with septal and valve defects and subsequent functional impairment (Gessler, 2002; Fischer, 2002, Fischer, 2004).

Combined deletion of Hey1 and HeyL leads to very similar cardiac defects because of impaired epitelial-to-mesenchymal transformation of endocardial cells. (Fischer et al., 2007)

Hubland Süd, Geb. B1 Hubland Nord, Geb. 32 Julius-von-Sachs-Platz 2 Fabrikschleichach Hubland Süd, Geb. B2 Campus Medizin