The Central Nervous System (CNS) is a complex network of numerous cell types. For example the human brain contains about 80 billion neurons associated with roughly 300 billion glial cells, and hundreds of different neuronal and glial cell types have been identified by morphology alone. Understanding how this myriad of different cell populations is generated is a fundamental question in neurobiology and can potentially lead to novel stem cell-based therapies for a diverse array of neurodegenerative diseases.
All the cell lineages of the CNS are derived from a common pool of multipotent progenitors. Neuronal progenitor cells are intrinsically limited such that a particular progenitor can only differentiate into a subset of cell types at a given time during development. A broadly accepted model proposes that progenitor cells progressively change their competence to generate different cell populations as development proceeds.
The goal of our research is to decipher the cellular and molecular mechanisms underlying neuronal progenitor competence and differentiation using a combination of cell lines, transgenic mouse models and biochemical approaches. We use the retina as a model system due to its relatively simple cytoarchitecture and high accessibility.
Some of the projects that we are currently pursuing in the laboratory are:
Role of microRNAs in the regulation of progenitor competence during retinal histogenesis.
Molecular mechanisms of cone photoreceptor specification and fovea development.
Additionally, the retina can be affected by a number of diseases that lead to progressive cell loss and ultimately irreversible blindness. These devastating conditions affect millions of people worldwide. Recently, advances in embryonic stem cell (ESCs) and induced pluripotent stem cell (iPSC) technologies have raised the possibility of custom-built cells for in vitro studies, drug screening and cell replacement therapies. In this direction, our group has successfully differentiated hESC and iPSCs into a variety of retinal cell types including photoreceptors and Retinal Ganglion Cells, and we are exploring the possibility of using these cells for transplantation purposes.
The neurons of the retina can be affected by a wide variety of inherited or environmental degenerations that can lead to vision loss and even blindness. Retinal ganglion cell (RGC) degeneration is the hallmark of glaucoma and other optic neuropathies that affect millions of people worldwide. Numerous strategies are being trialed to replace lost neurons in different degeneration models, and in recent years, stem cell technologies have opened promising avenues to obtain donor cells for retinal repair.
The laminated structure of the retina is fundamental for the organization of the synaptic circuitry that translates light input into patterns of action potentials. However, the molecular mechanisms underlying cell migration and layering of the retina are poorly understood. Here, we show that RBX2, a core component of the E3 ubiquitin ligase CRL5, is essential for retinal layering and function. RBX2 regulates the final cell position of rod bipolar cells, cone photoreceptors and Muller glia.
During early patterning of the neural plate, a single region of the embryonic forebrain, the eye field, becomes competent for eye development. The hallmark of eye field specification is the expression of the eye field transcription factors (EFTFs). Experiments in fish, amphibians, birds and mammals have demonstrated largely conserved roles for the EFTFs. Although some of the key signaling events that direct the synchronized expression of these factors to the eye field have been elucidated in fish and frogs, it has been more difficult to study these mechanisms in mammalian embryos.
Chromatin accessibility can be examined by DNase I digestion, and then revealed by the DNase I cleavage pattern. DNase I hypersensitive sites (DHSs) define the regulatory features of complex genomes (e.g., promoters, enhancers, insulators and other control regions).The combination of DNase I digestion and high-throughput sequencing (DNase-seq) has been used to map chromatin accessibility in vivo on a genome-wide scale. In this paper, we used this strategy to catalogue the CIS-regulatory elements of the developing mouse retina and brain.
The National Science Foundation began supporting ADVANCE initiatives in 2001, and has awarded over $130M in funding for a variety of programs. The most significant efforts seek to create permanent institutional transformation.