0:00
This is David Schaffer.
I'm a professor at the University of
California at Berkeley in Chemical
and Biomolecular Engineering,
Bioengineering, and the Helen Wills
Neuroscience Institute,
as well as director
of the Berkeley Stem Cell Center.
In addition, I'm co-founder of the
company, 4D Molecular Therapeutics.
And I'm going to be talking
about directed evolution
of novel adeno-associated
viral vectors for gene therapy.
0:23
So if we assess the current status
of the field of gene therapy,
which can be defined as the
introduction or delivery
of genetic material to
the cells of an individual
for therapeutic benefit.
There have been a number-- an
increasing number of successes
over the past few
years, and these include
bona fide clinical
successes for the treatment
of Leber's congenital
amaurosis, hemophilia B,
as well as familial
lipoprotein lipase
deficiency and x-linked
adrenoleukodystrophy.
Now the first three
indications I mentioned
were made possible through
adeno-associated viral vector
technology, which has been
increasingly successful as we
mentioned over the past few years.
Despite all of these
successes however,
a number of disease
targets are still
beyond the reach of current
gene transfer technology.
And that technology
must be made better,
which is the focus of my talk today.
1:09
So if we zoom into more detail next
slide on adeno-associated virus,
we see that this virus has
a relatively simple genome.
It simply contains
two Cis elements--
the inverted terminal repeats
that flank the genome.
And the genome only has two genes
that are open reading frames-- REP,
which encodes several proteins, as
well as CAP, which encodes three
proteins, as well
as a fourth protein
and an alternative reading frame.
Now this virus encodes as I
mentioned several versions
or several variants of the cap
protein-- 60 copies of which will
self assemble to create this
beautiful icosahedral structure--
and the rep protein which
is responsible for mediating
the replication as well as of
other functions of the viral genome
will then load this capsid with
it's viral genome payload for cargo.
So this virus is non-pathogenic.
It's never been associated
with human disease.
It's among the smallest of viruses
both in terms of genome size
at around 4.9 kilobases
of information,
as well as the dimensions
of the particle--
around 25 nanometers in size.
And a number of natural
variants of the virus
have been isolated, which
typically have variations
in the amino-acid sequence or
identity on these exposed loop
regions that you can see on
the viral capsid structure.
