Curriculum Vitae

Education

2005- 2008: Undergraduate study at University of Hannover (Germany)

Research experiences

2008-2011: Technical Assistant at Max Planck Institute for Biophysical Chemistry, Göttingen, Germany (Stoykova laboratory and Kessel laboratory).

2012-2003: Technical Assistant at Max Planck Institute of Experimental Medicine, Göttingen, Germany (Sereda laboratory).

4.2013-present: Technical Assistant at Institute of Neuroanatomy, University medical Göttingen (UMG), Germany (Tran Tuoc group, Director: Prof. Dr.  Jochen F. Staiger).

Publications

2019

RBM15 Modulates the Function of Chromatin Remodeling Factor BAF155 Through RNA Methylation in Developing Cortex.
Xie Y*, Hernandez RC*, Sokpor G, Pham L, Narayanan R, Rosenbusch J, Staiger JF, Tuoc T.
Molecular Neurobiology, https://doi.org/10.1007/s12035-019-1595-1, 2019.
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Chromatin remodeling factor BAF155 is an important regulator of many biological processes. As a core and scaffold subunit of the BAF (SWI/SNF-like) complex, BAF155 is capable of regulating the stability and function of the BAF complex. The spatiotemporal expression of BAF155 during embryogenesis is essential for various aspects of organogenesis, particularly in the brain development. However, our understanding of the mechanisms that regulate the expression and function of BAF155 is limited. Here, we report that RBM15, a subunit of the m6A methyltransferase complex, interacts with BAF155 mRNA and mediates BAF155 mRNA degradation through the mRNA methylation machinery. Ablation of endogenous RBM15 expression in cultured neuronal cells and in the developing cortex augmented the expression of BAF155. Conversely, RBM15 overexpression decreased BAF155 mRNA and protein levels, and perturbed BAF155 functions in vivo, including repression of BAF155-dependent transcriptional activity and delamination of apical radial glial progenitors as a hallmark of basal radial glial progenitor genesis. Furthermore, we demonstrated that the regulation of BAF155 by RBM15 depends on the activity of the mRNA methylation complex core catalytic subunit METTL3. Altogether, our findings reveal a new regulatory avenue that elucidates how BAF complex subunit stoichiometry and functional modulation are achieved in mammalian cells.

2018

Chromatin remodeling BAF155 subunit regulates the genesis of basal progenitors in developing cortex .
Narayanan R, Pham L, Kerimoglu C, Watanabe T, Hernandez RC, Sokpor G, Ulmke PA, Kiszka KA, Tonchev AB, Rosenbusch J, Seong RH, Teichmann U, Frahm J, Fischer F, Bonn S, Stoykova A, Staiger JF, Tuoc T.
iScience (Cell Press), DOI: https://doi.org/10.1016/j.isci.2018.05.014, 2018.
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The abundance of basal progenitors (BPs) - basal radial glia progenitors (bRGs) and basal intermediate progenitors (bIPs), in primate brain has been correlated to the high degree of cortical folding. Here we examined the role of BAF155, a subunit of the chromatin remodeling BAF complex, in generation of cortical progenitor heterogeneity. The conditional deletion of BAF155 led to diminished bIP pool and increased number of bRGs, due to delamination of apical RGs. We found that BAF155 is required for normal activity of neurogenic transcription factor PAX6, thus controlling expression of genes that are involved in bIP specification, cell-cell interaction and establishment of adherens junction. In PAX6-dependent manner, BAF155 regulates the expression of the CDC42 effector protein CEP4, thereby controlling progenitor delamination. Furthermore, BAF155-dependent chromatin remodeling seems to exert a specific role in the genesis of BPs through regulation of human RG-specific genes (such as Foxn4) that possibly acquired evolutionary significance.

Epigenetic regulation by BAF (mSWI/SNF) complexes limits neural stem cell proliferation by suppressing Wnt signaling in late embryonic development.
Nguyen H*, Kerimoglu C*, Pirouz M, Pham L, Kiszka KA, Sokpor G, Sakib MS, Rosenbusch J, Teichmann U, Seong RH, Stoykova A, Fischer A, Staiger JF, Tuoc T .
Stem Cell Reports, doi: 10.1016/j.stemcr.2018.04.014, 2018.
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During early cortical development, neural stem cells (NSCs) divide symmetrically to expand the progenitor pool, whereas in later stages, NSCs divide asymmetrically to self-renew and produce other cell types. The timely switch from such proliferative to differentiative division critically determines progenitor and neuron numbers. However, the mechanisms that limit proliferative division in late cortical development are not fully understood. Here, we show that the BAF (mSWI/SNF) complexes restrict proliferative competence and promote neuronal differentiation in late corticogenesis. Inactivation of BAF complexes leads to H3K27me3-linked silencing of neuronal differentiation-related genes, with concurrent H3K4me2-mediated activation of proliferation-associated genes via de-repression of Wnt signaling. Notably, the deletion of BAF complexes increased proliferation of neuroepithelial cell-like NSCs, impaired neuronal differentiation and exerted a Wnt-dependent effect on neocortical and hippocampal development. Thus, these results demonstrate that BAF complexes act as both activators and repressors to control global epigenetic and gene expression programs in late corticogenesis.

2016

mSWI/SNF (BAF) complexes are indispensable for the neurogenesis and development of embryonic olfactory epithelium.
Bachmann C*, Nguyen H*, Rosenbusch J*, Pham L, Rabe T, Patwa M, Sokpor G, Seong RH, Ashery-Padan R, Mansouri A, Stoykova A, Staiger JF, Tuoc T..
Plos Genetics, 2016. 12(9), *equally contributed authors
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Neurogenesis is a key developmental event through which neurons are generated from neural stem/progenitor cells. Chromatin remodeling BAF (mSWI/SNF) complexes have been reported to play essential roles in the neurogenesis of the central nervous system. However, whether BAF complexes are required for neuron generation in the olfactory system is unknown. Here, we identified onscBAF and ornBAF complexes, which are specifically present in olfactory neural stem cells (oNSCs) and olfactory receptor neurons (ORNs), respectively. We demonstrated that BAF155 subunit is highly expressed in both oNSCs and ORNs, whereas high expression of BAF170 subunit is observed only in ORNs. We report that conditional deletion of BAF155, a core subunit in both onscBAF and ornBAF complexes, causes impaired proliferation of oNSCs as well as defective maturation and axonogenesis of ORNs in the developing olfactory epithelium (OE), while the high expression of BAF170 is important for maturation of ORNs. Interestingly, in the absence of BAF complexes in BAF155/BAF170 double-conditional knockout mice (dcKO), OE is not specified. Mechanistically, BAF complex is required for normal activation of Pax6-dependent transcriptional activity in stem cells/progenitors of the OE. Our findings unveil a novel mechanism mediated by the mSWI/SNF complex in OE neurogenesis and development.

Ablation of BAF170 in Developing and Postnatal Dentate Gyrus Affects Neural Stem Cell Proliferation, Differentiation, and Learning.
Tuoc T, Dere E, Radyushkin K, Pham L, Nguyen H, Tonchev AB, Sun G, Ronnenberg A, Shi Y, Staiger JF, Ehrenreich H, Stoykova A.
Molecular Neurobiology, 2016. doi:10.1007/s12035-016-9948-5
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The BAF chromatin remodeling complex plays an essential role in brain development. However its function in postnatal neurogenesis in hippocampus is still unknown. Here, we show that in postnatal dentate gyrus (DG), the BAF170 subunit of the complex is expressed in radial glial-like (RGL) progenitors and in cell types involved in subsequent steps of adult neurogenesis including mature astrocytes. Conditional deletion of BAF170 during cortical late neurogenesis as well as during adult brain neurogenesis depletes the pool of RGL cells in DG, and promotes terminal astrocyte differentiation. These derangements are accompanied by distinct behavioral deficits, as reflected by an impaired accuracy of place responding in the Morris water maze test, during both hidden platform as well as reversal learning. Inducible deletion of BAF170 in DG during adult brain neurogenesis resulted in mild spatial learning deficits, having a more pronounced effect on spatial learning during the reversal test. These findings demonstrate involvement of BAF170-dependent chromatin remodeling in hippocampal neurogenesis and cognition and suggest a specific role of adult neurogenesis in DG in adaptive behavior.

Epigenetic regulation by BAF (mSWI/SNF) chromatin remodeling complexes is indispensable for embryonic development.
Nguyen H*, Sokpor G*, Pham L, Rosenbusch J, Stoykova A, Staiger JF, Tuoc T.
Cell Cycle, 2016. 2016, 18;15(10):1317-24, equally contributed authors
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The multi-subunit chromatin-remodeling SWI/SNF (known as BAF for Brg/Brm-associated factor) complexes play essential roles in development. Studies have shown that the loss of individual BAF subunits often affects local chromatin structure and specific transcriptional programs. However, we do not fully understand how BAF complexes function in development because no animal mutant had been engineered to lack entire multi-subunit BAF complexes. Importantly, we recently reported that double conditional knock-out (dcKO) of the BAF155 and BAF170 core subunits in mice abolished the presence of the other BAF subunits in the developing cortex. The generated dcKO mutant provides a novel and powerful tool for investigating how entire BAF complexes affect cortical development. Using this model, we found that BAF complexes globally control the key heterochromatin marks, H3K27me2 and -3, by directly modulating the enzymatic activity of the H3K27 demethylases, Utx and Jmjd3. Here, we present further insights into how the scaffolding ability of the BAF155 and BAF170 core subunits maintains the stability of BAF complexes in the forebrain and throughout the embryo during development. Furthermore, we show that the loss of BAF complexes in the above-described model up-regulates H3K27me3 and impairs forebrain development and embryogenesis. These findings improve our understanding of epigenetic mechanisms and their modulation by the chromatin-remodeling SWI/SNF complexes that control embryonic development.

2015

Loss of BAF (mSWI/SNF) complexes causes global transcriptional and chromatin state changes in forebrain development.
Ramanathan Narayanan, Mehdi Pirouz, Cemil Kerimoglu, Linh Pham, Robin J. Wagener, Kamila A. Kiszka, Joachim Rosenbusch, Michael Kessel, Andre Fischer, Anastassia Stoykova, Jochen F. Staiger, and Tran Tuoc.
Cell Reports, 2015. 13, 1–13
abstract link

BAF (Brg/Brm-associated factors) complexes play important roles in development and are linked to chromatin plasticity at selected genomic loci. Nevertheless, a full understanding of their role in development and chromatin remodeling has been hindered by the absence of mutants completely lacking BAF complexes. Here, we report that the loss of BAF155/BAF170 in double-conditional knock-out (dcKO) mice eliminates all known BAF subunits, resulting in an overall reduction in active chromatin marks (H3K9Ac), a global increase in repressive marks (H3K27me2/3), and down-regulation of gene expression. We demonstrate that BAF complexes interact with H3K27 demethylases (JMJD3, UTX) and potentiate their activity. Importantly BAF complexes are indispensable for forebrain development, including proliferation, differentiation and cell survival of neural progenitor cells. Our findings reveal a molecular mechanism mediated by BAF complexes that controls global transcriptional program and chromatin state in development.