B9 - Tucker

My laboratory is investigating primary cilia, a special organelle that we have found controls early events in the development of the fore- and midbrain, including morphogenesis, boundary formation, neurogenesis, nerve outgrowth, and layer formation. Primary cilia have recently been implicated as crucial sites of signal transduction and protein processing that are important for a wide range of developmental functions. For example, proteolytic processing of the transcription factor Gli3 occurs in primary cilia, and defects in the transport of proteins in and out of cilia can lead to severe developmental defects, such as exencephaly, polydactyly, and improper skeletal and renal formation and function.  The cobblestone (cbs) mutant was identified in a mouse ENU mutagenesis screen and is distinguished by cortical heterotopias, appearing at 10.5 d.p.c. as protrusions from the pial surface of the dorsal forebrain.  Mutants show severe defects in the formation of dorsomedial telencephalic structures such as choroid plexus, cortical hem and hippocampus.  Later embryonic stages show a failure to form superficial cortical layers such as the subplate, the cortical plate and the marginal zone. In addition, cbs mutants show a disruption in both pallial-subpallial and telencephalic-diencephalic boundaries.  Standard genetic mapping approaches and complementation analysis have identified cbs as a hypomorphic mutation in the Ift88 (Intraflagellar transport, 88 kDa) gene. The Ift88 protein plays an important role in the construction and maintenance of both primary and motile cilia, acting in a complex that is responsible for the intraflagellar transport of protein cargos. Although primary cilia are still to be found lining the ventricles of cbs mutant brains, a reduction in the proteolytic processing of the transcription factor Gli3 could be observed, as seen in other mutants in intraflagellar transport.  Finally, we have derived preliminary evidence implicating an upregulation of Wnt signalling as contributing to certain aspects of the phenotype.  Together, our results indicate a critical role for ciliary function in the developing forebrain.  In addition, our data suggest that cortical defects like those seen in the cbs mutant could be involved in the mental retardation seen in ciliopathies such as Bardet-Biedl, Meckel-Gruber, Joubert, and oral-facial-digital type I syndromes.

We propose to further investigate the role of primary cilia in fore- and midbrain development, using mouse models that allow for a finer spatiotemporal and genetic precision than has been achieved before.  The cbs mutant dies at 13.5 d.p.c. because of various heart defects, whereas the full Ift88 knock-out dies already at 10.5 d.p.c. Both of these developmental stages are too early to examine cortical layer formation and the developmental transition from neurogenesis to astrogliogenesis. Instead, we propose to use a conditional mutation of the Ift88 gene, in which a tissue-specific knock-out can be induced by crossing the mouse to a line expressing CRE-recombinase.  We will employ the nestin::CRE line, which will induce a specific elimination of Ift88 in neural precursors and their progeny, and the Emx1::CRE-ERT2 line, which will allow us to inducibly eliminate Ift88 from dorsal neural precursors and their progeny at any time between mid-gestation and early postnatal stages, using a single injection of tamoxifen into pregnant dams or newborns.  Using this allelic series of Ift88 mutants, we will investigate the following topics:

1) The role of primary cilia in cortical layering.

2) The role of Wnt signalling in the morphogenetic defects seen in the forebrain of the cbs mutant.

3)The nerve outgrowth defect in cranial ganglia seen in the cbs mutant.

Mein Labor untersucht die Funktion von Primärzilien, speziellen Organellen, die, wie wir entdeckt haben, an der Steuerung früher Ereignisse in der Entwicklung des Vorder- und Mittelhirns wie Morphogenese, Schichtenbildung, Neurogenese, Wachstum von Axonen und Gewebespezifikation mitbeteiligt sind. Wir schlagen daher vor, eine Reihe ENU-induzierter und zielgerichteter, induzierbarer Mutanten von Ift88, ein für die Funktion von Primärzilien entscheidendes Gen, zu verwenden, um hiermit drei Aspekte der Hirnentwicklung zu untersuchen, bei denen diese Strukturen eine wichtige Rolle zu spielen scheinen: 1) Cortexschichtung, 2) Kontrolle der Wnt Signaltransduktion im Cortex, und 3) Nervenwachstum im Mittelhirn.

Own project-related publications since the last application (2005)

Sanno, H., Shen, X., Kuru, N., Bormuth, I., Bobsin, K., Gardner, H.A.R.G., Komljenovic, D., Tarabykin, V., Erzurumlu, R., and Tucker, K.L. (2010) Control of postnatal apoptosis in the neocortex by RhoA-subfamily GTPases determines neuronal density. J Neurosci 30: 4221-4231

Eysyukov, V., Willaredt, M.A., and Tucker, K.L. (2009) Positional cloning of cobblestone, a mouse mutant showing major defects in brain development, identifies lft88 as a candidate gene. Impulse 7: 1-14.

Willaredt,M.A., Hasenpusch-Theil, K., Gardner, H.A.R., Kitanovic, I., Hirschfeld-Warnecken, V.C., Gojak, C.P., Gorgas, K., Bradford, C. L., Spatz, J., Wölf, S., and Tucker, K. L. (2008) A crucial role for primary cilia in cortical morphogenesis. J Neurosci 28: 12887-12900

Shakèd, M., Weissmüller, K., Svoboda, H., Hortschansky, P., Nishino, N., Wölfl, S., and Tucker, K. L. (2008) Histone deacetylases control neurogenesis in embryonic brain by inhibition of BMP2/4 signaling. PLoS ONE 3: e2668.

Wolff, S. B. E. and Tucker, K. L. (2008) Die Rolle der Histon-Acetylierung für Lernen und Gedächtnis. "The role of histone acetylation in learning and memory." Neuroforum 4/08: 274-279

Brachmann, I., Jakubick, V. C., Shaked, M., Unsicker, K., and Tucker, K. L. (2007) A simple slice culture system for the imaging of nerve development in embryonic mouse. Developmental Dynamics 236: 3514-3523.

Gao, L., Tucker, K. L., and Andreadis, A. (2005) Transcriptional regulation of the mouse microtubule-associated protein tau. Biochim Biophys Acta 1681: 175-81.

Own project-related publications prior to 2005

Original Papers

Bibel, M., Richter, J., Schrenk, K., Tucker, K. L., Staiger, V., Korte, M., Goetz, M., and Barde, Y.-A. (2004) Differentiation of mouse embryonic stem cells into a defined neuronal lineage. Nat Neurosci 7: 1003-1009

Korets-Smith, E., Lindemann, L., Tucker, K. L., Jiang, C., Kabacs, N., Belteki, G., Haigh, J., Gertsenstein, M., and Nagy, A. (2004) Cre recombinase specificity defined by the tau locus. Genesis 40: 131-138

Plachta, N., Bibel, M., Tucker, K. L., and Barde, Y.-A. (2004) Developmental potential of defined neural progenitors derived from mouse embryonic stem cells. Development 131: 5449-5456

Wernig, M., Benninger, F., Schmandt, T., Rade, M., Tucker, K. L., Bussow, H., Beck, H., and Brustle, O. (2004) Functional integration of embryonic stem cell-derived neurons in vivo. J Neurosci 24: 5258-5268

Heins, N., Malatesta, P., Cecconi, F., Nakafuku, M., Tucker, K. L., Hack, M. A., Chapouton, P., Barde, Y.-A., and Gotz, M (2002) Glial cells generate neurons: the role of the transcription factor Pax6. Nat Neurosci 5: 308-315

Tucker, K. L., Meyer, M., and Barde, Y.-A. (2001) Neurotrophins are required for nerve growth during development. Nat Neurosci 4: 29-37

Yamashita, T., Tucker, K. L., and Barde, Y.-A. (1999) Neurotrophin binding to the p75 receptor modulates Rho activity and axonal outgrowth. Neuron 24: 585-593.

Reviews

Tucker, K. L. (2002) Neurotrophins and the control of axonal outgrowth. Panminerva Medica 44: 325-333.

Tucker, K. L. (2001) Methylated cytosine and the brain: a new base for neuroscience. Neuron 30: 649-652

Tucker, K. L. (2001) In vivo imaging of the mammalian nervous system using fluorescent proteins. Histochem Cell Biol 115: 31-39

Kerry Tucker

IZN- Interdisziplinäres Zentrum für Neurowissenschaften

Universität Heidelberg

Im Neuenheimer Feld 307

69120 Heidelberg

Phone: 06221-548687
Fax:     06221-544952
email:  Kerry.Tucker(at)urz.uni-hd.de