Ellen J. Hoffman, MD, PhD: How can zebrafish help us to understand genetic and biological mechanisms in autism spectrum disorders?

December 01, 2020

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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.