cc >> Tom Zinnen: Welcome,
everybody, to Wednesday Nite at the Lab.
I'm Tom Zinnen. I work here at the University
of Wisconsin-Madison Biotechnology Center.
I also work for UW Extension Cooperative Extension.
And on behalf of our partners at the Wisconsin Alumni Association
and Wisconsin Public Television, welcome to Wednesday Nite
at the Lab. We do this every Wednesday
night, 50 times a year. Tonight I'm delighted to be able
to welcome Jennifer Laffin to Wednesday Nite at the Lab.
She'll be talking about her work at the Wisconsin State
Laboratory of Hygiene and telltale clues using genetic
tests to diagnose diseases in children.
Jennifer is from Kaukauna, Wisconsin, and got her BS degree
here in genetics in 1996. She went over to Iowa City and
got her PhD in genetics in 2003 and came back to Madison
with a fellowship in 2006 and then as an assistant professor
in 2008, and just this year she became co-director of the
clinic. I look forward to her talk.
Please join me in welcoming Jennifer Laffin
to Wednesday Nite at the Lab. [APPLAUSE]
Jennifer Laffin: Thank you. Thank you, everyone.
It's a pleasure to be here. So I'm Jennifer Laffin.
I'm co-director of the Clinical Genetics Laboratories at the
State Lab of Hygiene. The State Lab of Hygiene houses
the Clinical Genetics Laboratories at the UW.
So we have sections in cytogenetics, molecular genetics
and biochemical genetics. So that covers all the areas of
clinical genetic laboratory testing.
So it's a really great place to be right now.
And in the audience is my co-director, Dr. Raca.
We oversee the cytogenetic section and the molecular
genetic section. So tonight I'm just going to
talk a little bit about the types of testing that we do, and
then give you some examples of the types of cases that come
through our door. So you can kind of get a feel of
what happens to a specimen, how do we use our different
techniques and how do we use our tools to try to get at some
answers for our patients. And then learn something as well
about the biology and kind of feed the research and feed the
clinical side as well. So all the sides kind of work
together to try to bring better patient care.
So the types of testing, the types of specimens that we work
on, so we do everything from prenatal testing where we take
amniotic fluid specimens, chorionic villi specimens,
so little placental biopsies, to oncology testing.
So we do a lot of testing of patients that have leukemias,
lymphomas and tumors to try to identify genetic markers that
can be both prognostic and drive treatment as well.
And we also do a lot of testing for individuals who have
developmental issues. We do testing for fertility,
anything that has an genetic aspect.
And genetic aspects, as you're learning more and more, is
hitting all fields of medicine. So genetics is really growing
and growing fast. So tonight I'll be talking about
cytogenetics and molecular genetics and how we have an
opportunity here to use our research tools as well as our
clinical tools to help our patients.
So I'll start with a little primer in cytogenetics.
So cytogenetics 101. So we have the opportunity to
work at all levels or all resolutions of genetics.
So we start with chromosomes which are composed of our DNA
protein and they carry our genetic material in our cells.
And then go all the way down to molecular so we can look at
bases as well. So cytogenetics is the study of
structure and function of chromosomes--
Yeah? >> Could you tap your
microphone? Thank you.
That activates it. >> Okay, sorry.
Okay, so in order to see chromosomes we need living
tissue that's actively dividing. So if you remember the types of
specimens that we have, we get blood specimens where you hope
that cells wouldn't be actively dividing in your peripheral
blood and we also get tumor specimens as well which are
actively dividing, amniotic fluid specimens actively
dividing. So we need living tissues in
order for it to go. So we have cells that we either
induce to go into mitosis or into cell division or we look at
cells that are already actively dividing.
So here we have a couple diagrams of just the cell cycle,
what happens. And here's, on the right hand
side, we have a diagram of really what's happening looking
at the DNA inside of those cells.
So at interphase we have DNA that's all strung out so that
you can get activation of genes and silencing of genes, and then
as cells go through mitosis, we need those chromosomes to
condense and then normally what would happen is the chromosomes
that condense line up at the metaphase place and then be
split into the two daughter cells.
So what we do is we need to capture those chromosomes at
their most condensed state. So we poison those microtubules
that would normally connect and then pull the chromosomes to
their daughter cells. So we depolymerize those
microtubules and then hold those cells in metaphase.
So after we've done that, we bloat the cells a little bit.
So we use a hypotonic treatment that swells the cells and helps
with chromosome spreading. So what needs to happen is we
need to put those chromosomes on a microscope slide so we can
actually visualize them. So we swell the cells and then
we fix them so they stay put. So that also lyses any red blood
cells that might be still floating around but it stops
that hypotonic swelling. And then this is the art part of
cytogenetics. So it's the slide making and the
staining portion. So when we drop the chromosomes
there, we have to make sure that everything happens just so
so you don't end up with chromosome soup.
So when you drop the cell suspension on a microscope
slide, that the chromosomes don't get spread off into every
which way. We need them to stay in a nice
little puddle so that we can identify one nucleus, one
nucleus, one nucleus. So we can count the chromosomes
and look at their banding. But we don't want them so tight
that they're all crumpled up and laying on top of each other that
you can't really identify which chromosome is which.
So we drop the suspension of these fixed cells on to a
microscope slide. They need to dry at exactly the
right temperature and the right humidity so that you don't get
overspreading, underspreading, and that everything will stain
and band nice. The slides then get baked and
then they're treated with trypsin.
So these are pictures from our laboratory of what's happening.
So actually the image over here is one of our drying chambers.
So a technologist will be there with a patient's specimen, drop
the slide, put the slide in the drying chamber, this has exactly
the right humidity and temperature so that the
chromosomes dry nicely, and then we can check spreading and
concentration at the microscope right next door here.
But then after they're baked, then they go through a process
of trypsin, so that eats the proteins a little bit, and then
stain. So we use the Giemsa stain.
And then they get cover-slipped and then sent out to our
technologists for analysis. So what happens most often, now
we have a slide scanner, an automated slide scanner that
will go through and try to look for metaphases for us, but we do
often for like prenatal specimens sit at the scope and
look through the whole entire slide looking for the best
metaphase spread. So this image right up here is
what you would see under the microscope.
So the cell is spread and each of these are individual
chromosomes. So there should be
46 chromosomes, and then a technologist will go through and
find one, one, make sure you have both chromosome ones and go
band for band and make sure that all the bands are in the right
orientation and that they're actually present.
So there aren't deletions or duplications or extra pieces of
that. So then we also the capabilities
of or we have software that allows us to electronically cut
out the chromosomes and then arrange them in a karyogram.
So right here you can see all the chromosomes.
We have chromosome 1 through 22 are autosomes.
And then males have an X and a Y and females have two Xs.
So with every case that we have we got through and we make sure
that everything is as it should be or if there's a particular
abnormality that we're expecting, that that's there.
So the next step up in resolution that we have, we have
fluorescence in situ hybridization and then more
molecular genetic techniques. So fluorescence in situ
hybridization, or FISH, allows us to look at a very specific
part of the genome. So what we can do is we can take
the piece of the genome that we're interested in, we can
label it with a fluorescent probe and then stick it to the
genome. So you make that little
fluorescent probe and then you can hybridize it, you can
hybridize it either to interphase nuclei and count the
dots or you can hybridize it to a metaphase spread and actually
see which chromosome that it's hybridizing to.
And there are a lot of different probe types that we can use to
answer very specific questions. So we have whole chromosome
paints. Those don't get used as often
anymore now that we have a ray comparative genomic
hybridization. But if there's a particular
piece of a chromosome that you really suspect is coming from a
particular chromosome, like for example this image up here, it
was suspected that we know that the banding was consistent with
chromosome 13, is that extra material that's attached to that
chromosome 13, is that from the Y chromosome?
So you can paint that and see that yes, in fact, there is
chromosome 13 right here and that this red material right
here came from chromosome Y. There are centromere enumerator
probes. So we can look and count to see
how many of each chromosome there are.
We use those often in amniotic fluid specimens.
So looking for the common trisomies.
So 13, 18, 21 and we can look for the sex chromosomes very
quickly without looking for rearrangements, just know that
there are two 21s, two 13s, two 18s, and so on and so forth.
And then locus specific indicators in the cocktails of
multiple probes can be manipulated in different ways
that we can look for very specific chromosomal
rearrangements as well as microdeletion syndromes and
duplications. So this example, these examples
down here, this is from the DiGeorge region.
So this is a recurrent microdeletion syndrome.
So we have a piece of DNA that's very specific to the region that
is commonly deleted in the 22Q deletion syndrome.
So we can look for that and you can see in this specimen here's
the normal 22. You have the green is the
control probe that kind of marks that chromosome as this is
chromosome 22. And then the red is that
region that is commonly deleted in this syndrome.
So you can see there's a normal 22 and the 22 over here has that
region deleted. We can also, so as far as the
manipulation of these, you can take locus specific probes and
arrange them so that you can look for particular fusions or
particular breaks in a gene. So if you know a gene is
commonly broken in a particular disease, you can take two probes
and then look for the break apart in the abnormal cells.
The molecular genetics is a lot less visually fancy at the very
beginning. The end is still really cool.
So we generally start with a blood specimen from our
patients. We get rid of the red blood
cells and keep the white blood cells where all the DNA is
stored. And then some of our assays do
require RNA but most of our assays require DNA.
And we precipitate out those proteins, and then you can
precipitate the DNA out of solution.
So you can watch that DNA come right out of solution.
So if you think each cell in your body has about six feet of
DNA, each nucleated cell has about six feet of DNA, and it's
really fun to just watch that ball up and then be used for a
really fancy assay like sequencing.
So this is just some examples. I won't go into each of these
techniques individually because that will probably take an
entire night in and of itself, but we can go on and we can look
at things like epigenetic effect.
So this gel up here is from our Prader-Willi Angelman assay that
looks for differences in methylation at a particular
region on chromosome 15. This is an example of array
comparative genomic hybridization where we can look
for copy number changes. So we can look for very small
deletions and duplications within the genome.
We can count the number of copies of a particular gene
using quantitative PCR or quantitative RT-PCR.
We commonly use southern blotting.
We use southern blotting for fragile X testing.
And then of course there's sequencing where you look base
for base at a particular region of interest.
And then we do fragment analysis as well.
So first and foremost, our goal is to provide the best patient
care that we can. So the clinical laboratories,
above all, patient care is it what we're about.
So our testing is used for treatment and prognosis,
stratification into the different studies, we have a lot
of studies that the university participates in and we do the
clinical testing for those. And then, as part of our
academic mission, we do have research projects on the side.
So as we learn things, the exciting thing about genetics is
we get a lot of results, sometimes, especially the
scanning techniques where we don't know exactly what it
means. There's something not right and
we have an opportunity to really take the next step, in some
cases, and really look at is this the gene involved, what
does it do and what can we do about it, is this something that
other patients might be interested in as well.
So this brings in new techniques and new testing into the
clinical laboratories. So I'm going to start with a
few, I'll have a few case reports or case examples of the
types of things that we have come through our lab.
So the first case is a five-year-old girl who presented
to her family practice clinic with leg pain.
So in this case there's a lot of other clinical features that I
won't get into in depth, but they did a CBC and they found
many abnormal B cell lymphocyte blasts.
So the diagnosis was B cell acute lymphoblastic leukemia.
But now the diagnosis doesn't just end there.
So you take it the next step further.
They had requested cytogenetics to look for common
rearrangements that happen in leukemias so that you can look
at different treatment options, you can talk about prognosis and
do other stratifications into potential studies and so forth.
So we did her chromosomes and this is what we found.
Can anybody identify what is wrong with this chromosome?
Yeah? >> It looks like in one of the
chromosome 14 samples has been a large deletion.
Right. So there's something wrong with
the chromosome 14. It looks like there's a whole
bunch of it that's gone. Anybody else?
How about 10. >> 10, chromosome 10, right.
So there's something very wrong with chromosome 10.
And if you compare the banding of the abnormal 10 with the
banding of 14, you can see that those two chromosomes have
switched material. So there's a translocation
on 10 and 14. There are two other
abnormalities. >> 16.
16. You guys are good.
This is good. Right, so 16.
16 has material at the bottom of it.
9. >> And 9.
Great. You guys are hired.
So 16 has some material on the bottom of it that doesn't look
quite right, but then when you look at the top of chromosome 9
you can see that 9 and 16 have swapped material.
So you have two translocations in this karyotype.
So then my job is to take it the next step farther.
So it's fine to say we have two translocations, but now we need
to know are there any important genes at those break points that
we can tell right now, have any of these translocation occurred
before. Do you have a question?
What causes translocation? >> What causes translocation?
There are probably a lot of things that cause translocation.
So you could have mutation that causes abnormal crossing over.
You can have breaks and rejoining.
It depends, a lot of things depend on where and how you see
it. When you see it in an oncology
specimen, it can sometimes just be sheer chaos.
So there are molecular mutations that happen that cause abnormal
swaps. There can be repetitive regions
that get deregulated. There are all kinds of reasons
that translocations happen. But there's not one particular
reason why they happen. So there are some, I'll talk
about one recurrent translocation in humans, but
other than that there's not really a whole lot of recurrent
translocation just in general. So there are some that happen
over again in specific types of cancer, but those mechanisms
aren't really well known. Yeah?
Are they limited to certain chromosome numbers or types?
No, they're not really limited to certain chromosome
numbers or types. So there are certain cases
like chronic myeloid leukemia. So that has a 9-22
translocation. That is the indicator for that
particular disorder. But in most cases, there are a
whole host of translocations that have been seen in this
disorder and that disorder, especially when you start
talking about oncology. And I didn't bring any really
crazy karyotypes. But there are some, like
myelomas you can have karyotypes that have 100 chromosomes and
all kinds of translocations. Especially solid tumors, you can
have chromosomes you can't identify.
You know it's chromosomal material but you can't really
figure out where the material came from.
So in some cases it's kind of predictable, but predictable we
don't exactly know why. But it keeps it exciting and it
helps us identify, so with all these different types of
translocations that helps us identify new genes to go after
to see, okay, if we don't physically see a break in a
translocation in them, are there molecular things happening that
we can't see at a chromosomal level.
So if we start going after the genes at the break points, can
we identify things earlier and faster so that we can intervene
with treatments a little bit sooner.
So when I looked at these two translocations, there were four
genes of interest. So the 9-16 translocation had
the PAX5 gene at the chromosome 9 break point, and it had core
binding factor at the chromosome 16 break point.
So my hypothesis was with this that this is a translocation
that helped solidify it as a B cell lineage.
So if this translocation was present, it was going to look
like a B cell type abnormality. And then there was a 10-14
translocation. And at that translocation we
had, okay we're good? There were two genes the BMI
gene and then the T cell receptor alpha delta.
So the T cell receptor alpha delta we see commonly we have a
clinical probe that we use for it involved in T cell disorders,
but if it was in conjunction with this BMI-1 gene, could that
be just what's fueling the proliferation.
So now this is a good hypothesis for the step forward.
So we can now take this out of the clinical realm and, of
course with the consent of our families, we can take this into
the research realm and really look at these genes and try to
figure out, make the first step, make sure that those are the
genes that are actually involved and then move that out further
into the research realm to try to figure out how important are
these genes in the disease and can we learn something from the
way that they're functioning. So towards that, we were able to
make some FISH probes. So we were stepping it up one
more notch in resolution. And in this one we did see right
off the bat that our T cell receptor has been translocated.
So you see here this is a normal cell.
The five prime end of the gene and the three prime end of the
gene are together. And then over here this is a
metaphase. You can see the normal
chromosome 14 right here, and then you can see the abnormal,
that little tiny chromosome 14, the derivative 14 and then the
derivative 10. So the three prime end of the
gene is now on chromosome 10. So you can see that in both
metaphase and in the interphase cells.
So the next question was, well we know that TCR is involved in
the translocation, so the question is, is the BMI one gene
also involved? So we took a look.
You can go online and you can find back clones that are
specific to your region of interest.
You can label them up and you can look to see how your clone
reacts in your particular specimen.
So we took this RP11 clone that's near the BMI-1 gene, and
then we labeled that in blue. And then we looked to see is
that with the TCR gene at all. And you can see here, here's the
normal 14. So we have the red and the
green. And here's that derivative 14.
That's the driver. So that's what we're
hypothesizing is what's driving the disease, what's making the
proliferation of all of these cells.
And we have the derivative 10 and a normal 10 over here.
So you can see that those markers are there.
So the next question was looking at that 9-16 translocation.
So what about PAX5 and what about this core binding factor?
It also has been involved in myeloid disorder translocations
as well. So we know that this core
binding factor, this MTG16 is a known culprit in leukemias
already. So when we look at clones, so
these are clones that we purchased.
We labeled those up. And when you hybridize those to
cells, you can see that that PAX5 and that core binding
factor are fused in these cells. So that's what's driving, that's
what we're hypothesizing is driving that B cell commitment.
So now we've take be it to a step where now it has to be
handed off for further research, but we have the opportunity,
it's exciting to have the opportunity to really look into
these disorders more and get more answers to physician and
patient questions. So our second case is kind of a
common site in a clinical genetics clinic.
So often what the physicians over there see are kids with a
lot of developmental delay, no real handles, so when they come
in the door there aren't any real handles that their family
practice doctors have. They just know they're not
meeting their milestones, they're having global issues,
but after spending, so the clinical geneticists really
spend a lot of time asking very specific questions and trying to
get some more answers that might not be readily apparent to a
family practice doctor. So in this case we have a
five-year-old girl, could be any young age, with a history of
she's awake at night, very tired during the day.
So her sleep cycles are all off. She has a history of
self-injurious behavior. So like head banging and things
like that. And difficulty toilet training.
So these might be phenotypes that really wouldn't be
striking to anybody but coming into a clinical genetics clinic,
the physician thought this sounds a lot like Smith-Magenis
syndrome. So what comes to us is I would
like to do a FISH test looking for this very specific deletion
on chromosome 17P. So we do that test.
And what you can see here, we have, again, so the control
probe is in green. So this marks these chromosomes
as this is chromosome 17. And then you have your region of
interest. So the red probe is for that
Smith-Magenis syndrome region. And you can see in this patient
that that region is in fact deleted.
So this is a nice case in that we're able to get answers, but
often it's a series of the diagnostic odyssey.
So we really need to get better at finding more disorders and
finding efficient ways to get at answers for families.
So the physician was suspicious of this, but it's important to
get a very distinct clinical diagnosis through testing for a
lot of reasons. So this opens up access for
special education opportunities, speech and physical therapy.
There are pharmacological management options for
regulating that sleep cycle which makes everybody in the
family a lot happier when everybody sleeps at night and
everybody is awake during the day.
Things you learn to appreciate. And then there's surveillance of
very specific things about this syndrome that you would look for
during healthcare maintenance that you might not look for if
you didn't have a very specific diagnosis.
So looking at kidney and thyroid function, monitoring for
scoliosis and eye changes. So the next case is meant to
highlight how different techniques can be complimentary.
How when you look in one area, don't find an answer, you look
in another area using a little slightly different view or
slightly different resolution you can get the answer that
you've been looking for. So case three, a 20-year-old
male. The phenotype is developmental
delay, cataract, high myopia, midface hypoplasia, so a very
flattened faces, and spondyloepiphyseal dysplasia.
So they have vertebral abnormalities.
And so this phenotype was very specific.
It was a little bit more severe but it was specific for Stickler
syndrome. And the physician had ordered
sequencing for Stickler syndrome.
So you would think sequencing would find everything.
It would find the mutation, it would find exactly what you're
looking for. But the sequencing came back
normal. And so the next question was,
okay, well, the phenotype is more severe than what you would
expect so let's look at a whole genome survey for copy number
analysis. So the requested technique was
array comparative genomic hybridization.
So just to give you a very brief background of the technique.
So this is like a giant FISH assay.
So you label your test or your patient, we label our patients
in green. You label control or reference
DNA in red, and then you cohybridize them in equal
amounts to a microscope slide that has on it spots that are
very specific to all regions of the genome.
So instead of doing, looking at one or two regions of the
genome, we can look at 44,000 plus regions of the genome.
So each of the spots on the slide has lots of little pieces
of DNA. So there are 70 base pair
strings printed in little spots. So then when you hybridize your
patient and your reference DNA to it, you should get yellow.
So whatever is in your test should be in your control if
everything is normal. And when you have a loss or a
deletion in your patient, you can don't have that labeled
portion in your patient pool. So what you see coming up is
reference. So what you see is red.
And these slides, these slides are not scanned by the naked
eye, they're scanned by a laser and all of that data is put into
a computer and then visually represented for you to do the
analysis. So in this diagram here with
have the patient has a deletion. So what you see is red, and
every other area of the genome is yellow because the patient is
reference is equal. So in this particular patient,
this is the diagram of what we would see coming off of the
computer in the lab. So this is of chromosome 12 and
you can see that in this patient there's a big deletion on
chromosome 12. It's a 2.73 megabase region,
but it includes the gene for Stickler syndrome
as well as 19 other genes. So the 19 other genes kind of
help identify the severity. But with the size of the
deletion, if you went in and sequenced that gene, what are
you sequencing? You're only sequencing the one
allele that's there. The other allele is gone.
So you would get normal. So it was a nice complement to
testing that was already done. So the next few cases that I'm
going to talk about really focus more on prenatal genetics.
So we do prenatal diagnosis for prognosis.
So a lot of times we'll get specimens in for advanced
maternal age. So do we see the presence of the
common trisomies that are associated with advanced
maternal age. So 13, 18, 21, sex chromosome
abnormalities. Can there be, if we do find
something, is there a medical intervention.
So sometimes there are medical interventions for these things.
And then inheritance. So what is the recurrence risk.
So has there been an abnormal ultrasound.
If there's been an abnormal ultrasound, you look at the
genetics, can we see anything that would give the parents any
idea of what recurrence might be.
So this example is one that we see often.
So we have phenotypically normal potential parents.
So the reason for referral, so in this particular case we have
a phenotypically normal male, a partner with a history of
miscarriage, that happens often, a family history of multiple
pregnancy losses. So his mother had multiple
miscarriages. A partner with an ongoing
pregnancy. Three copies of chromosome 13
detected by prenatal FISH, where is that extra 13 coming from?
Those types of things. The requested testing is
standard chromosome analysis and a peripheral blood specimen.
And what you can see here on this patient is a Robertsonian
translocation carrier. So can you all see which
chromosome? 13.
So chromosome 13 has chromosome 14 attached to it head to head.
So this individual has all the genetic material he needs to be
phenotypically normal, but when you try to force his chromosomes
to go through miosis you get nondisjunction and problems.
So the reproductive consequences in this case, so there's risk of
affected children, so there's risk of trisomy 13 or 14 in this
particular case. And then there are affects of
uniparental disomy. So it's important that you get
the appropriate amount of DNA from mom and the appropriate
amount of DNA from dad. If you don't have that exact
mix, and it is chromosome specific so there are some
chromosomes that are more affected than others, but if you
don't get that mix you can end up with a phenotypic effect
because you have too much of your genome that came from mom.
Even though you have the right number of chromosomes.
And then what is the risk to other family members?
So is this translocation new in this individual or did they
inherit it in a balanced fashion from a parent?
Do they have carrier parents? Are there potential siblings
that might be affected as well? And it also offers the
opportunity for preimplantation genetic diagnosis.
So now if we have a very specific abnormality that we can
look for, we can look for that in the preimplantation period to
increase the chances for a successful pregnancy.
The next example is, again, a phenotypically normal pregnant
female. The reason for referral is a
fetus with growth retardation. So the fetus isn't growing as
fast as it should. So the request was for FISH for
13, 18, 21, X and Y, so or standard prenatal panel looking
there. And then chromosome analysis.
So those are often paired because the FISH analysis
doesn't look for physical rearrangements, it just looks
for presence or absence or too many of a particular chromosome.
So we did the prenatal panel. And you can see over here these
are the probes for chromosome X and 18.
So you can see that this baby is a girl.
And then on the right you have the probes for chromosome 13 and
21. So it looks like there's the
right number of chromosomes, at least with regard to the common
trisomies. When with you look at the
chromosomes, we find too many. So you can see at 22 there is
this little extra chromosome. So immediately the technologists
in the lab suspect Emanuel syndrome.
So this looks like the product of an individual who has a
common recurrent translocation that's, like the only recurrent
translocation in humans, between chromosome 11 and 22.
So when this looks like the derivative 22 from that
translocation. So just to confirm this, because
the banding is not exactly descript on those tiny
chromosomes, so we do some extra testing just to make sure that
the material on that chromosome does in fact come from
chromosome 11 and chromosome 22. And through a series of FISH
tests, we do, in fact, see that here we see what's in red is
11Q, so it's that long arm. You have your two normal 11s in
this individual, but then that little tiny chromosome has 11
material in it. And then when looking for
chromosome 22, you can see that it also has 22 material.
So it is, in fact, from that 11-22 translocation.
So getting that extra chromosome, in this particular
case, happens because of three-to-one segregation.
So those of you who enjoy looking at segregation, it's
always kind of fun to see how chromosomes can potentially
segregate. So in this case the segregation
usually happens in a three-to-one fashion.
So you end up with that extra derivative chromosome.
So the 11-22 translocation is a recurrent translocation in
humans. The unbalanced segregants are
usually from a three-to-one segregation, leading to 47
chromosomes with that extra derivative chromosome.
So this is just an example, it's not as clear as I'd like it to
be, but of what the carrier parent would look like.
So they, too, have all the genetic material to be
phenotypically normal, but when you try to force their
chromosomes to go through miosis, to make gametes, things
run amok. And these types of things we see
at a reasonable rate when we do fertility testing, for instance.
So approximately one in 500 people phenotypically normal has
some kind of chromosomal abnormality that would generally
go undetected, and then for fertility reasons they do
chromosomal work up and we'll find a balanced translocation.
And so then that's an answer that you can then look for and
that's where genetic counseling comes in and we talk about what
the possibilities are there. So the importance of the
diagnosis. So when we see translocations
like this you can anticipate the medical needs at birth.
So in this particular case it's involved with congenital heart
disease. They can have kidney
abnormalities, diaphragmatic hernias, talking about
inheritance. So where did the chromosome come
from? How far back can we track it?
Are there other people who might be at risk?
And then to really get an idea of what the developmental
expectations are. So with a can we do to give this
patient the best that we can? >> What are the diagnoses of
these? >> So what's all involved with
it? And that's another important
thing. So a lot of people go online and
see what's involved with Emanuel syndrome, and you'll find a
whole list of things. Any genetic disorder, the
Internet is really kind of a scary place to go.
That's where you go to your genetic counselors and your
clinical geneticists because they give you a list of a
million things because this individual has this genotype,
this individual has this genotype but they also have this
phenotype. So the phenotype kind of builds,
builds, builds but not one person has all of those things.
So there can be a whole host of things to look at.
But really the things that you look at are, in this particular
case their concerns are with congenital heart disease, kidney
abnormalities. [INAUDIBLE]
Yeah. So this is a photo that I took
from GeneReviews. So you can go to:
genereviews.org It's a great place to go to get
genetic information, and it just shows a little bit about, you
can describe a phenotype in words but looking at pictures
will really give you an idea of what things can be different in
a phenotype and what things can be the same.
So looking at phenotype in people is a lot different than
looking at phenotype in other models.
So there are a lot of things that are different but a lot of
things that you can really point out as being similar or the
same. And then to try to make those
genotype/phenotype correlations, and that's really where a lot of
the research in human genetics is going right now to try to
identify what those genotype/phenotype correlations
are because a lot of times it really isn't well characterized.
But those are the questions. Those are the questions that
patients and parents want to know.
What can I expect? What can I do?
How can I fix it? And towards that we have to do
more and more work on the abnormalities that we do find to
try to identify gene function, how it works in an organism and
how it affects development. There's a whole bunch of things
that won't be solved by necessarily...
I have a question. >> Yeah.
What are the diagnostics of these types of children?
So these children have exactly that karyotype.
So they have that extra derivative 22.
So they're exactly-- if I go back, can I go back?
So they have the karyotype, can I go back?
They have this. So when you see Emanuel
syndrome, you will see chromosomes that look like this.
But the individuals will look a little bit different because
they all have a different background, but when you look at
just the chromosomes, they'll have the extra derivative 22
from that 11-22 translocation.
So, like I had mentioned before though, too often things are
apparently normal. So a lot of work needs to be
done. So we have new mutations to be
discovered, technology costs need to be reduced.
So from the clinical laboratory perspective we want to offer our
patients the best and not have to pay a lot of money to get an
answer. And then to come up with some
testing algorithms that are really efficient.
So you can, with the tests that are available, they are very
specific. So can we narrow it down faster
and better to get answers for our patients?
So that is all I have this evening.
[APPLAUSE] Thank you very much.