National Institute of Environmental Health Sciences (NIEHS)

Persistent inflammation is a pathogenic determinant in many common human diseases, including rheumatoid arthritis, Crohn’s disease, multiple sclerosis, and psoriasis, while playing a key role in the development of type-2 diabetes, obesity, certain forms of cancer, and neurodegenerative conditions such as Parkinson’s and Alzheimer’s diseases. The laboratory of Dr. Blackshear has identified tristetraprolin (TTP) as a protein that acts to restrict inflammation in mice by destabilising the mRNA of pro-inflammatory cytokines such as TNF, GM-CSF, CXCL1 and CXCL2. Mice where an instability-conferring element within TTP’s own mRNA was deleted using homologous recombination were remarkably resistant to inflammatory disease. Most importantly, these mice did not exhibit any pathology, presumably because of the relatively modest over-expression of TTP that was otherwise subject to normal regulation.  

However, studies of TTP’s biochemical and molecular activities have been hampered by the existence of three other members of the same protein family in the mouse.  Each of these proteins exhibits similar biochemical activities in cell transfection experiments and in cell-free assays, but knockout mice of each have led to dramatically different phenotypes, involving early development, hematopoiesis, and placental function rather than inflammation.  For this reason, we will use the fruit-fly Drosophila melanogaster, which expresses only a single TTP family member, known as TIS11. Using genetics, biochemistry, transcriptomics, and proteomics we will explore the role of TIS11 and extrapolate findings to experiments in mammalian systems at NIEHS.

The human placenta is the first organ of the embryo and it is functional immediately after implantation. Before fetal organogenesis, the placenta holds a multi-functional and unique role as a physical, chemical, and cellular barrier. It alone orchestrates the chemical communication between mother and fetus. Most of this communication is mediated by the secretion of specific placental peptide hormones (hCG, hPL, etc.) into the maternal bloodstream. Despite these hormones having developmental and irreplaceable functions, little is known about their intracellular life: synthesis, intracellular traffic, secretion, and degradation. More importantly, many pregnancy disorders are associated with lower expression and levels of these hormones in circulation, such as fetal growth restriction and preterm birth. The cell biology of these diseases is not well understood.

With the recent advance in human placenta organoid development and novel culture techniques of trophoblasts derived from stem cells, we can now finally interrogate the fundamental questions about placental hormones' intra and extra-cellular fate. In combination with the diverse set of advanced imagining methods available between the co-mentors of this project (advanced fluorescence and cryo-electron microscopy), innovative multi-omics techniques, and advanced biochemistry and cell biology approaches, we propose to 1) discover the diversity of secretory granules (SGs) expressed in and secreted from the human placenta; 2) implement a novel in vitro secretomics approach to determine the molecular machinery that regulates the secretion of the SGs and their content; 3) validate the mechanisms using human placenta and isolated trophoblasts from donated tissue and new placenta organoids culture.

The successful candidate will have the opportunity to train on several modern imaging techniques and learn about the fundamentals of placenta development and physiology while using a multi-disciplinary approach in a team of expert cell biologists from both institutions and generating impactful basic and applied research.

Midbrain dopamine neurons have fundamental roles in reward learning and movement control, and their dysfunction is associated with various disorders in particular Parkinson’s disease. Recent studies have shown substantial diversity in the activity of these neurons depending on where in the striatum their axons project. In our recent experiments we recorded the activity of dopamine axonal terminals while systematically manipulating stimuli, actions and rewards in a precise behavioural task. While the activity of dopamine projections to ventral regions of striatum mainly reflected rewards, dopamine axonal projections to dorsal striatum encoded contralateral stimuli and actions with negligible representation of reward value. These findings raise the questions of whether dopamine signals across striatum encode specific aspects of associations between stimuli, actions and rewards during learning, and whether these anatomically-specific dopamine signals are impaired during Parkinson’s disease. This project will address these questions using a combination of imaging, computational and behavioural experiments in healthy mice as well as mouse models of Parkinson’s disease. In Oxford University (Lak lab), we will use recent genetically–encoded dopamine sensors in combination with fiber photometry to monitor the dynamics of dopamine signals across the striatum while healthy mice perform a learning task guided by sensory stimuli and rewards. These results will provide a foundation for examining these dopamine signals during Parkinson’s disease, which will be performed at NIH (Cui lab). Using MitoPark mouse line (with progressive and robust phynotype of Parkinson’s disease), we will examine the dynamics of striatal dopamine signals using photometry during learning tasks established in healthy mice in Oxford. In analysing the data, we will use learning models to relate dopamine signals with normative computational models of decision making and learning. The project is primarily experimental in nature but will provide an opportunity to develop computational skills. The project will provide fundamental insights into behaviourally-relevant computations that dopamine signals across the striatum encode, and will uncover how these neuronal computations change during Parkinson’s disease. For further information visit: https://www.niehs.nih.gov/research/atniehs/labs/ln/pi/iv/index.cfm and www.laklab.org

*This project is available for the 2021 Oxford-NIH Pilot Programme*

Pluripotent stem cells, such as embryonic stem cells (ESCs), can be used as a model system to study the molecular basis of fate-specification during early mammalian development. They can also be used to derive various types of cells for disease modeling, drug discovery, regenerative medicine, and environmental health sciences. To fully realize these potentials of pluripotent stem cells, it is important to understand the molecular mechanisms that regulate the pluripotent state. We have previously carried out a genome-wide RNAi screen in mouse ESCs and identified a list of novel factors that are important for pluripotency maintenance. Among them, we are currently investigating the function of the Ccr4-Not mRNA deadenylase complex and the INO80 chromatin remodeling complex in ESCs, somatic cell reprogramming, and mouse development using biochemical, genetic, genomic and single cell analysis approaches. In addition, we are developing new genetic and genomic methods to identify and probe genes involved in stem cell fate specification. We are applying these methods in pluripotent and germline stem cells to better understand the maintenance, transition, resolution, and re-establishment of the pluripotent state.