For decades, scientists have relied on animal models like the mouse, the nematode worm Caenorhabditis elegans, and fruit fly Drosophila melanogaster to study basic biological processes and disease states. These systems are highly valuable but have shortcomings when it comes to investigating Angelman syndrome (AS) and its effects on the brain. Simpler organisms are easier to grow and manipulate in the lab, but lack the brain complexity of mammals, and some, like C. elegans, do not have the ube3a gene at all. Work in mice and other rodents has been critically important in identifying ube3a as a key AS gene and establishing ube3a paternal gene activation as a viable therapeutic strategy for AS, but we all know that mice are not humans. Methods that utilize human neurons, in all their complexity, can be critical to helping to understand and advance novel AS treatments.
Human neuronal cells can be grown in a lab, and this has been a valuable approach that has yielded a large amount of significant data in the Angelman research space. This is known as 2-dimentional neuronal models. Much can be learned from cells growing in a dish, but cultured cells do not interact with each other to form the complex neuronal networks found in the actual human brain. Knowing that disruption in the communication between 2 neurons (synapse) is responsible for many of the challenges seen in those living with AS (synaptopathy), a way to understand and test this is in a laboratory is needed – one that combines the complexity of tissues as they exist in a living organism (in vivo) with the simplicity and ease of cell culture in a lab (in vitro). This can transform drug development.
One of the key advances in biological science research over the past decade has been the creation of organoids. Organoids are clusters of cells derived from highly differentiating cells (pluripotent stem cells), often taken from some skin or blood cells, that have been coaxed to mature into a tissue-like state in a laboratory dish. Organoids display many of the properties of real tissues but are much easier to work with. They can be genetically manipulated quickly and grown by the hundreds. Organoids are especially suitable for work involving the human brain. Human neuronal organoids have been shown to form self-directed neural networks with electrophysiological properties reminiscent of those in the brain itself, similarto what we see on an EEG when evaluating brain waves. This is an opportunity to test neuron function in a laboratory and screen many different drug or gene therapy candidates to understand quickly if they have promise to work in neurons of those living with Angelman syndrome.
A new FAST grant, awarded to Drs. Amay Badnonkar and Albert Keung, collaborators at North Carolina State University, aims to harness the power of organoids for Angelman syndrome research. The overarching goal of the grant is to develop methods to make relevant measurements on brain organoids, including things like voltages and catecholamine concentrations, which can measure the function of neurons, in a high throughput manner so many drugs can be tested at once and candidates can be quickly and efficiently screened. The technique, developed in the laboratories of these researchers, will be invaluable in testing the potential efficacy of different AS therapeutic candidates, where they can directly measure the impact on human neuron function, not just the levels of UBE3A expression. Dr. Bandodkar, an assistant professor of Electrical and Computer Engineering, will provide the engineering expertise in developing and building new types of sensors that can be used in these organoids. Dr. Keung, whose work had been funded by FAST in the past, is known for his work in synthetic biology and will oversee the biological aspects of the project, including creating the human cell lines and organoids.
Organoid biology is a rapidly developing area, but it is a field still in its early days. There is much excitement about future applications of organoids in a variety of research areas, that up until now have been difficult to study outside of live animal models. This is an opportunity to take a human blood cell with Angelman syndrome (through a simple blood draw), isolate the youngest cells (stem cells) and create neurons from those cells that have Angelman syndrome. From there these cells can be nurtured to grow into a brain organoid. This brain organoid, which is a 3D complex structure resembling the human brain, provides the ability for researchers to highlight the challenges of neuronal communications in AS and discover ways to fix it. This new work funded by FAST will help the AS community get in on the ground floor as organoid research continues to develop and allow for more therapeutics to be tested.