Research On The Roles Of Cep120Gene And Wdr34Gene In The Ciliogenesis And Sonic Hedgehog Signaling Pathway

Parti:Talpid3-binding centrosomal protein Cep120is required for centriole duplication and proliferation of cerebellar granule neuron progenitorsGranule neuron progenitors (GNPs) are the most abundant neuronal type in the cerebellum. Sonic hedgehog (Shh) secreted from Purkinje cells is essential for the proliferation of GNPs and cerebellar development. Shh signaling occurs in primary cilia originating from the mother centriole. Centrioles replicate only once during a typical cell cycle and are responsible for mitotic spindle assembly and organization. Recent studies have linked cilia function to cerebellar morphogenesis, but the role of centriole duplication in cerebellar development is not known. Here we show that centrosomal protein Cep120is asymmetrically localized to the daughter centriole and interacts with Talpid3(Ta3), also a centrosomal protein. This asymmetrical localization is dependent on Ta3. Cep120null mutant mice die in early gestation with abnormal heart loping. Inactivation of Cep120in the central nervous system leads to hydrocephalus and severe cerebellar hypoplasia, which are attributed to the loss of cilia on ependymal cells and the failed proliferation of GNPs, respectively. The mutant GNPs are also unable to respond to Shh signals. Cell biological studies show that the loss of Cep120results in a failed centriole duplication and consequently ciliogenesis, which together underlie Cep120mutant cerebellar hypoplasia. Thus, our study for the first time links a centrosomal protein necessary for centriole duplication to cerebellar morphogenesis. Part2:Wdr34negatively modulates mouse sonic hedgehog signal transduction through affecting retrograde intraflagellar transport in primary ciliaBidirectional(anterograde and retrograde) motor-based intraflagellar transport (IFT) governs cargo transport and delivery processes that are essential for primary cilia growth and maintenance and for hedgehog signaling functions. The cytoplasmic Dynein2motor complex that regulates ciliary retrograde protein transport contains a heavy chain ATPase/motor subunit, DYNC2H1, along with other less well functionally defined subunits. Wdr34encodes a WD40repeat-containing protein orthologous to Chlamydomounas FAP133, a dynein intermediate chain associated with the retrograde intraflagellar transport motor. Recently researches indicated Wdr34plays an important role in development of human. To investigate the profound biochemical function of Wdr34gene, we generated a Wdr34gene knock out mouse model successfully. We found Wdr34protein located in microtubulin, cilia and both centrioles. Wdr34mutation affecting retrograde intraflagellar transport function in cilia inhibited Shh signal transduction, resulted in these abnormal phenotypes. Meanwhile, Wdr34mutation prevented DYNC2H1and DYNLC1from entering into cilia, therefore, Wdr34gene plays a quite important role in Cytoplasmic dynein2. AC3protein’s entry into cilia requires Wdr34protein, which is to say, Wdr34protein is not only to be function as retrograde intraflagellar transport motor protein, but also as an anterograde motor. Wdr34also promotes growth of centrioles and cilium, plays an important role in cell’s growth and mitosis, may be associated with cancerogenesis.