Identification and validation of proteins with Siah-degron-motifs that are essential for neuronal migration.

• Applicant: Dr. Jan Kullmann
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2014 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 255966672

Neuronal migration is essential for the morphogenesis of the developing brain and defective migration leads to profound developmental and cognitive disorders, such as lissencephalies with resulting epilepsy and mental retardation. In order to design strategies to prevent or treat such disorders, it is necessary to understand the molecular mechanisms that regulate neuronal motility and migration initiation. Recently, the Seven in Absentia homolog (Siah) E3 ubiquitin ligase has been identified as a novel regulator of the partitioning defective (PAR) proteins. Siah was isolated as a PAR-binding protein by a yeast-two hybrid screen and inhibits the germinal zone exit and migration of cerebellar granule neurons through the degradation of PAR3. An in silico and functional screen for further Siah targets revealed 22 proteins with Siah degrons and potential implications in neuronal migration. The aims of the proposed project are to validate whether these proteins are indeed degraded in a Siah-dependent manner and to test whether they are sufficient and/or necessary for germinal zone exit and neuronal migration. Siah-dependent degradation of the candidate proteins will be tested in a heterologous expression system (HEK293 cells) where Siah and a candidate protein will be expressed simultaneously. Afterwards the relevance of newly identified Siah-degraded proteins for germinal zone exit and radial migration of cerebellar granule neurons will be tested in organotypic cerebellar cultures. Subsequently the signaling pathways of the proteins that regulate germinal zone exit and/or neuronal migration will be determined via fluorescence-tagged adhesion receptors. Taken together this project will increase the knowledge about molecular mechanisms that control germinal zone exit and neuronal migration tremendously and could provide an avenue to discover new diagnostics and potential treatments for neuronal positioning disorders.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Dr. David J. Solecki