Ellen J. Hoffman, MD, PhD: How can zebrafish help us to understand genetic and biological mechanisms in autism spectrum disorders?
December 01, 2020Ellen J. Hoffman, MD, PhD: How can zebrafish help us to understand genetic and biological mechanisms in autism spectrum disorders?
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Assistant Professor in the Yale Child Study Center and of Neuroscience
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- 00:02Hello, thank you for coming
- 00:04to my virtual poster.
- 00:06It's great to have the
- 00:08opportunity to tell you about
- 00:10the research that my lab is doing.
- 00:12We use zebrafish as a model
- 00:14system to help us to understand
- 00:16more about the biology of autism.
- 00:19So just walk you through my poster to so
- 00:22to give you a little bit of background.
- 00:25In recent years,
- 00:27we've identified over 100 genes
- 00:29that are strongly associated
- 00:30with the risk for autism.
- 00:32But we really don't have an
- 00:35understanding of what these
- 00:37genes do in the developing brain,
- 00:39and so our goal is to to use a
- 00:42relatively simple nervous system
- 00:44model system to try to help us to
- 00:47understand more about what these
- 00:49jeans are doing in the developing
- 00:52vertebrate brain as a path to gain a
- 00:54better understanding of the biology
- 00:56of autism and to possibly develop
- 00:59improved pharmacological treatments.
- 01:01So why do we study zebrafish?
- 01:03There are really three key advantages.
- 01:05One.
- 01:06They have external development
- 01:08of transparent embryos so they're
- 01:10fully transparent,
- 01:11so we can visualize in real time what it is.
- 01:16A developing vertebrate brain.
- 01:18We can visualize basic neural
- 01:20developmental processes.
- 01:21Second, zebrafish are highly tractable,
- 01:24so they're easy for to use for
- 01:27performing large scale drug screens
- 01:29to identify novel compounds.
- 01:31And finally,
- 01:32with the introduction of crisper
- 01:34as a gene targeting method.
- 01:37It's possible to to easily genetically
- 01:40manipulate the zebrafish so that
- 01:42we can disrupt the function of
- 01:44these autism risk genes.
- 01:45And to date,
- 01:47my lab has already generated
- 01:49zebrafish mutants in at least 10
- 01:51different high confidence autism
- 01:53risk genes and so to give you an
- 01:56over overview of the workflow,
- 01:57if you look at the central panel and
- 02:00the idea is that we generate these
- 02:03zebrafish mutants that lack the
- 02:05function of these autism risk genes.
- 02:08And then we take advantage of
- 02:10their transparent embryos.
- 02:12The ability to visualize the entire
- 02:14brain during development so that
- 02:17we can see how the disruption of
- 02:19these specific genes affects the
- 02:21development of specific neural cell types.
- 02:24And then we can also perform
- 02:27these large scale behavior based
- 02:29drug screens where we can pipette
- 02:31individual fish into the wells of
- 02:34a 96 well plate and track different
- 02:36aspects of their locomotor activity
- 02:38and ask how that changes when these
- 02:41autism risk genes are not functioning.
- 02:43So how does this affect as
- 02:46simple behavioral circuits?
- 02:47And then we can use this as the
- 02:49basis for screening different
- 02:51compounds to identify potential
- 02:53drug candidates that we could then
- 02:56test further in the million systems.
- 02:58And so here's an overview.
- 03:00What we're doing in terms of the
- 03:03aims of our project.
- 03:05We were going to use all these
- 03:07autism risk gene mutants identified
- 03:09differences in their brain structures
- 03:11so we can understand more about
- 03:14how these genes affect effect.
- 03:17Overall, brain development,
- 03:18brain structure and to see if we can
- 03:21identify commonality's in terms of
- 03:23how these genes affect affect brain
- 03:26development. Second, we're going to.
- 03:28As I said,
- 03:29do large scale drug screens to identify
- 03:32compounds that might that might reverse
- 03:35abnormalities in the behaviors of these fish.
- 03:38So we look at very simple behaviors
- 03:41like rest, wake behavior, rest,
- 03:43wake circuitry, and visual startle
- 03:44circuitry as a readout of looking
- 03:47at sensory processing behaviors.
- 03:49And finally, because zebrafish are
- 03:51fully transparent and they have a
- 03:53relatively simple nervous system,
- 03:55we can visualize changes in brain activity.
- 03:58In real time in awake behaving zebrafish,
- 04:01I'm using a new microscope technology
- 04:04that my lab is developing.
- 04:07And so I'll take you over
- 04:09to the right hand panel,
- 04:11take you through some of our our
- 04:14results so some of our published data
- 04:16has shown that when we disrupt one
- 04:19particular gene that's associated
- 04:21with both autism and epilepsy,
- 04:23contacta associated protein two,
- 04:24that this this disruption
- 04:26leads to abnormalities,
- 04:27particularly in inhibitory
- 04:28neurons in the forebrain.
- 04:30So what you're looking at here are
- 04:32transgenic lines that allow us to
- 04:35visualize these different populations of.
- 04:37Nerve cells and what we can see is
- 04:39that in the forebrain when we disrupt
- 04:41the function of this autism risk gene,
- 04:44it leads to a loss of these
- 04:46inhibitory neurons.
- 04:47I'm second in the same fish.
- 04:49We performed a large scale behavior
- 04:51based drug screen and interesting Lee.
- 04:54What we found was that drugs
- 04:56that had estrogenic activity were
- 04:58able to suppress the behavioral
- 04:59abnormalities in these mutant fish
- 05:01and so specifically we finally found
- 05:04that disrupting this gene led to a
- 05:06phenotype of nighttime hyperactivity.
- 05:08So these fish were two active
- 05:10during the night and what we found
- 05:12through our screen was that drugs
- 05:14that had estrogenic activity were
- 05:16able to specifically suppress.
- 05:18That phenotype and so now through
- 05:21collaborations we are testing
- 05:22these drugs in a mouse model of
- 05:25contact and associated protein.
- 05:26Two to see if this candidate molecule
- 05:28that we identify Nurse screen
- 05:30can translate 2 million systems.
- 05:32And finally we're now looking across
- 05:34all of our different autism risk
- 05:37gene mutants to try to see if we can
- 05:39identify what we call points of convergence.
- 05:42Can we see similarities in the way
- 05:44that these genes affect simple
- 05:46behavioral circuits at the behavioral
- 05:49circuits controlling?
- 05:50The processing,
- 05:50and So what we're able to do is identify
- 05:53what we call a behavioral fingerprint
- 05:56for each mutant associated with the
- 05:58loss of function of each risk gene
- 06:01using very simple behavioral assays.
- 06:02Looking at rest,
- 06:04wake activity or visual startle
- 06:05activity to begin to identify ways
- 06:08in which these genes affect the
- 06:10nervous system in similar ways,
- 06:12and we're going to use these points
- 06:14of conversions and these behavioral
- 06:16fingerprints as a way of identifying
- 06:18potential new pharmacological candidates
- 06:20that we're currently testing in the lab.
- 06:23And in terms of the future
- 06:25directions of the work,
- 06:27we're now testing compounds that we
- 06:29think could be potential drug candidates
- 06:31that target these neural circuit
- 06:33deficits in the zebrafish mutants.
- 06:35And we're developing an in collaboration
- 06:37with the Yale Center for Neuro Technology,
- 06:40and you two photon light sheet
- 06:43microscope that will allow
- 06:44us to image the entire brain of an awake
- 06:47behaving zebrafish in under one second.
- 06:50With the idea that it can help us to identify
- 06:53circuit mechanisms that are disrupted.
- 06:56When these autism risk genes
- 06:58are not functioning properly,
- 07:00so I want to 1st thank funding sources
- 07:03of which the support and the Child
- 07:05Study Center for the support for
- 07:08this research and thank you very much
- 07:10for listening to my virtual poster.