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.
All these cell lineages 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 and neocortical 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.
