Genome Sequence Databases

Genome Sequence Databases


Welcome to this course functional genomics
So in the previous lectures we looked into uhhh the use of microarrays and how they can
be used to understand gene expression profile that’s high through put approach to look
at genome wide expression pattern that was a powerful technique people have developed
to understand large scale difference in the expression patterns Even for those genes that
have not been characterised before Similarly even understanding the genome the
way we look at the genome and that been characterised as change for a time and in today’s uhhh
lecture we are going to look into how the genome has been characterised and the approach
is that we use to uhhh sequence the genome to understand the complexity that comes along
with the sequence and how that information can be used for example in the medicine or
understanding how humans evolved understanding how other species have evolved This has become
uhhh the challenge and this has been met already with powerful tool that that have been developed So we will be looking into some of those uhhh
you know advancements in this field So let us look into uhhh the slide this slide
sort of summarizes how the genomic advancements since the human genome projects that was launched
sometime in early 90s have changed the way the genome being studied and understood So
what has been shown is the summary of a topic we already discussed uhhh this includes the
how the classic example of how Mendel you know sort of understood the possibility of
DNA being or the genes being there or how they are segregating and then the early 1919s
and up to 1954 or so when the DNA structure was understood and the tools for DNA sequencing
have evolved and since 1990s there has been an explosion with regard to how the genome
is looked into So you can see that in 1990 there was an agreement
as to there has to a consortium uhhh involving several labs to sequence the human genome
with that initiative uhhh the methods by which the genome sequenced as a tremendously changed
and many new novel techniques have come in and and different research groups and countries
have started sequencing several other genomes of moral system For example east genome sequence was completed
in 1996 and then you have the worm genome has completed in 98 in 2000 drosophila sequence
has been completed and equalize sequence also complete in 1997 and so on So with however
with uhhh with the completion of the human genome that has been explosion in terms of
the way the genome has been analysed and that is being sort of you know of discussed in
the next slide So this sort of summarizes as what had happened
since uhhh the completion of human genome sequencing in 2004 2005 it pretty much we
have done all the sequence analysis as well and then a large number of sequence have been
sequence For example chicken you know another example very good moral system to understand
the biology specially the development biology Rat is another very good model for specially
drug discovery and dog genome sequencing because this is one that is domesticated and a large
number of mutants that you see different breeds are available and that has become again powerful
tool to understand what genetic change causes a particular uhhh again that has been sequenced
and then you have the closest to the Humans the chimpanzee even that genome is sequenced
and and with with uhhh such advancement what has happened is that people started looking
beyond just looking at the genome sequencing So what you see here in this particular uhhh
section is the first genome wide association study a topic you discussed a little later
but just to give an introduction this is to understand how variation between different
individuals can confer a given individual uhhh resistant to a particular disease or
more susceptible meaning at higher risk of developing a disease and and that is what
lead to what is called the project In this what is being looked at is not the human genome
sequence but the variation in the human genome sequence So uhhh in this kind of developments you know
led to even far reaching consequence For example there are you know when when the human genome
sequence is uhhh sequencing project was initiated it was a very very expensive offer so governments
were involved public money has been put into because this cannot be really done by individual
labs or individuals but things have changed with technology that is emerging even first
you know direct to consumer vole genome test meaning one could sequence the anti of genome
and understand as to what are the variants What are the variants exists than what risky
could have and a so on so this has emerged in early 2000 uhhh in mid-2000 and then different
other models for example honey bee sequence is started and then you have with all these
advancement sequence and that co-relating with the geno type you also need to have very
good data base which can integrate all this data So you have these NCBA data base for
geno type and phenotype that has come in and then other another monkey sequence has come
in and ad what you called as again looking into the variation in the human genome The world compressed what is called as case
control study consortium you know approach is started like you recruit thousands of individuals
that are normal from a given geographical ethnic region and then look into individual
who have a particular disease that representing the same population and then compare the genome
o see what are the variants that make an individual uhhh at risk of developing a disease or uhhh
you know resistance like you know your risk of developing diseases rather low So that is break through something which started
and then uhhh you know the given different for example uhhh different countries have
started sequencing their own population Reason being uhhh the human genome sequence has come
from certain few individual that probably not represent all the population that live
on the earth The Chinese government you now initiated a sequencing of their you know population
2007 and then and people started understanding how possible the mammals evolved for example
so there is a one connecting link platypus that genome was sequenced and there like ways
in African population The genome was sequenced to understand how
humans evolved overtime uhhh and then it went to further investigation especially the cancer
genome because we know now cancer is not caused by you know uhhh in single gene it is caused
by defecting multiple genes and that could be restricted to the cells that have become
cancer and it could vary from one individual to other or when within an individual it could
vary from one population to other So if you can understand what has gone what
kind of changes have happened in the sub population of the cancerous cells in terms of genome
than it becomes extremely you know critical in in or important in uhhh useful in treating
the cancer because one it gives an understanding as to what is the subtype or we looking at
different groups of cancer or it is this one particular type and second by looking into
genes that have been altered you would be able to tell her the duck such you are able
to control their individuals Such kind of initiative you can see there
are many especially if our cancer all so on In 2009 again another Asian country the Korean
how developed you know programme to sequence their own genome and then it is just not the
sequence but beyond sequence how genome has been altered What you called as epigenetics
something that we discussed sometime back which talks about how For example methylation at the chromatin level
or at the DNA level can change the way the genome functions So that is the initiative
in 2009 where there was a uhhh method by which we are able to identify bases that have been
methylated even at the chromatic level you know modification are been looked at and then
some of the commercial animals like species for example bromine genome has been sequenced
and then uhhh you know you have a large number of mammalian species you know the genome sequence
is completed in around 2009 So we have sort of understanding as to how
different the different mammals and how we evolved and so on So 2010 onwards you know
things have changed more dramatically now we have uhhh large number of what is called
as the association studies have began like people looked into the old genome to understand
what kind of changes that or combination of changes can make an individual more susceptible
for a given disease and this is a landmark because 500 genome wide association study
is published by 2010 that also tells how the approach is evolved over time and how useful
it is become in identifying the risk factors and of course you have other countries joining
in For example southern uhhh African genome sequence
initiated and there are many large number of such functional genomics approaches also
has been initiated one is for example limitations you go on imitating about 1000 individual
genes in the mouse and understand what phenotype they they developed This something that we
discussed in the previous lecture how to understand the function that is from genotype to phenotype
consortium and then encode projects to understand the uhhh expressions and their correlation
with the function and then also understanding how humans have evolved Some of the ancestral possible species that
once lived connecting the primates with the humans understanding our history evolution
and then another landmark project that was initiated was the thousand genome pilot project
uhh that was sort of completed gain here to understand not just the genome sequence but
to understand what are the variation that exists between different population here the
idea used to complete the genome sequence of minimum 10000 individuals uhhh in a larger
context but to begin with it was a pilot study 1000 genome which was completed which will
tell you the sequence variants within the coding sequence non-coding sequence regulatory
sequence and so on and these are not restricted to certain population They have uhhh we will discuss that they have
uhhh you know they selected population representing the entire human race So this is uhhh you
know advancement so we are going to look into what really made a difference therefore we
could take up such challenging you know genome projects but such advancements are not restricted
only to the other country Even within our country India the government
of India has funded a project what is called as a Indian Genome Variation Consortium because
the Indian population cannot be called as a single population There are huge variation
within different population that are present given ethnic group or the people who speak
a particular language and have community casts tribes and so on And and therefore there is a larger uhhh gain
if you can understand what is the sequence variations that are unique to each one of
the sub-population that represent so called Indian population So there was a consortium
mode in large closed to 100 individuals genome sequence to at least at the exome level meaning
coding sequence they have been sequenced and that was initiated and you like wise there
was a pan Asian population initiative meaning all the Asian countries including India China
Singapore you know Japan Indonesia Malaysia They joined together to sequence the and understand
the variation within the genome of the Asian populations because there are lot of migration
that happened between the population therefore that would one help us to understand the similarity
and difference amongst the population and to to understand for example what makes a
genome unique uhhh and and that reflex in terms of you being in a better condition or
you being not in a better condition For example we know that Indians have very high risk of
developing diabetes but the risk of developing other disorders like uhhh Dementia Alzheimer
are much lower as compared to the western population So it looks like that could be something that
is there in the genome that make you more susceptible for a given disease or resistance
to that So this kind of approach is would help us to identify the signatures if not
uhhh the real mechanism but even if you understand the signatures that identifies such sub groups
One could start working on understanding how the signatures really may modulate the cell
tissue and organism such that you know you more susceptible or resistance to given disease So this is schematic uhhh representation to
tell about how the genomic research has changed over years This is something that that we
already discussed the human genome project 1990 and 2000-2003-2004 the draft sequence
was completed So you can see the understanding the structure of the genome in with reference
to uhhh the human genome at least is done by pretty much is completed now because you
know we have sequenced the genome the sequence is available but what is important is understanding
the biology of the genome What is it mean so you have a sequence uhhh
so you have sequenced it What really it means that is becoming extremely challenging because
there was an expectation that when the genome sequence was completed that you would understood
the biological bases of you know the majority of disorders you will be able to treat them
and so on but it really did not help in that way We only understood what is the sequence
but it has really thrown a more challenges than what has been anticipated For example one of the expectations was we
will have more number of genes as compared to the other species because we are more complex
and more successful but with with you know the completion of human genome We found that
we are not really having a large number of genome uhhh genes as compared to other species
The complexity is (()(16:00) so to understand that you know the biology of the genomes you
know how do they function It has become challenging and that is what we can see here in from 2004
to 2010 such kind of approaches have come in so we want to understand the genome that
is what you call as functional genomics So how genome regulates its function right
so that is the functional genomics and then from 2000 that is still you know sort of ongoing
You can see that its sort of picked up and we have you are talking about how a genome
is organizes dynamics and its transcription variations all these things are coming up
but that you know sort of trying to understand what possibly you know contributes to normal
function of the genome The more challenging would be to understand how variation in the
genome or change in the genome can contribute to the disease progression uhhh genesis and
so on That is going to be challenging and that is
you know is already in progress You could see that we will talk about it little later
There are number of studies we are understood what is a genetic cause and how that can possibly
alter the way genome functions in terms of expression in terms of uhhh miss expression
and so on So that is this study currently been investigated and and that would uhhh
you know lead to much more impact in the way we manage disease that would result in what
is called as advancing the science of medicine So we right now the focus has been to understand
what goes wrong as a result you would have a disease but can we fix that Can we alter
can there be a therapy based on your genomic understanding and that is something that is
going to come that is going to be the challenge uhhh the next decade and obviously in a such
advancement if and when made we are going to have you know improve your health condition So it is not that you would change uhhh your
what you called as life expectancy you may live you know in 90 years 100 years but the
focus has been that can we have a healthy living without much of a problem So this is
not the longevity but you know whether your it is the healthy living that is what it is
as long as you live you are happy and you do not have any uhhh discomforts that itself
is a huge relief to the ageing population because which time with industrialization
and increase in the life expectancy Over the time we are going to have the aged
population the ratio in most of the countries is going to increase including India and 50
years from now is going to be a huge burden because you are going to have a more of aged
population So that becomes a huge challenge for countries to handle so if you could cut
down the expenditure on the medicine than you are able to live better right because
for every-thing is connected to money So these are the expectations that is how it is projected
and we will see some of these issues I am just showing you one such website uhhh
which I would encourage all of you to go and look into This is called as a genome browser
uhhh from the University of California uhhh website and that talks about the encyclopedia
of DNA elements it talks about how the sequence of the DNA and it is association with transcription
modification involvement in disease and everything So if you really want to understand what uhh
the genome revolution has done to our understanding of the genome This is one of the very good websites and
very educational you can go and there are many good links where you can understand how
it has really you know change the way we understand the genome So one is to off course the uhhh
the data if you are interested in analysing the data but you can also look into some of
the applications like for example the genome browser It tells you how the genes are organized
right so that gives you an idea that how the genes are organised in the genome and off
course there are large number of you know uhhh links that are there you can go on looking
to for example what genome addition you are looking at what cell type you are looking
at and so on Experimental matrix one can go on look into that I will show you one such snapshot of the genome
browser this is I going to show you a region of chromosome that is chromosome 6Q24 this
is a gene that our group has been working on for a long time This is called as CPM I
just showed you to appreciate what you can get out of the genome browser So it clearly
tells that this you can see here there is a red line that is the region in which the
gene is localised You can see this is chromosome 6 right this is short arm of the chromosome
and this is the long arm of the chromosome and this is the position what you call as
a 246Q24 that is where the gene is localised and you can see all these things So what does it mean so you see that there
are lines here these are the regions that represent exons So this is the five of the
gene and this is the three of the gene Exon 123 and 4 so it clearly tells you how many
exons are there and it not only tells you how many exons are there but it also tells
you whats the distance between each exon So you can go on look into these are the nuclear
tide bases you can calculate exactly the distance and the span of the gene and in addition it
is also telling you how many variants of the transcripter and you can see that you know
there are you know so many trans 123 that start from here to here but you see there
are differences for example this transcript starts here and ends here and there are 1
transcript you have 4 exons but in between there is an intra So how many different splice variants exists
even that that are represented you can see here that is that this for the human and then
it also talk about uhhh the uhhh what you call as methanation pattern of the chromatic
So what you can see here is the you can see like mountains these are segments that are
being shown to have methylated chromatic so that is you know for example astellation is
show here right and it also talks about for example transcription you can see that these
are how many transcript maps two different regions You can see there are mountains where ever
you have exons obviously I going to have more transcript array sequence representing the
exons and this one talks about chip data we will talk about a little later what are the
regions on which some transcription factors come and bind and you can see that there are
transcription factors that are binding close to the three primer end but majority you can
find at the five end of the gene Obviously because if these are the factors that regulate
the genes expression they need to bind to other 5 ends beyond that you can see that
conservation for example if you look into the sequence and then look at the analogous
regions are homologous region in other species how much is the sequence conservation right You can see that where ever you have for example
exons the sequence conservation pretty high You can see that even in chicken and zebra
fish you find that the sequence homologous will exists right where as in intron then
you do not obviously see much of the sequence similarity because these sequence are not
under selection pressure They can undergo changes because they does not affect the gene
function but there are changes happening in the coding sequence it would affect the gene
functions therefore such changes are not altered Now that talks about conservation but we come
at the bottom of the screen and these are the hips that each bar represent regions in
which you have variations in the human genome remember I told you about 1000 genome project
and such project really talks about what is the variation at the genome level across the
population and you can see that there are large number of sites you know in the genome
that show multiple variants Now whether these variants alter the gene
whether the alterations affect the way the gene functions whether that changes in the
gene function you know provides you any risk of developing any disease or other conditions
These are all something that one needs to investigate but certainly that tells you that
there are variations and that could be informative The last bar that is shown in here is the
repeat right so the genome as you know that uhhh as large number of repeats and the repeats
helps in the evolution in different ways If you have read in books that you understand
that genes have evolved via duplication because of the repeats because it repeats itself at
times in non-homologous recombination and as a result you have domains that are duplicated
are genes that are duplicated and and that help in the evolution So what you see here is that there are repeats
there are present across the gene and these repeats may have an influence or may not an
influence on the gene function we never know but what could perhaps you may want to understand
is that repeats at times can make genome unstable as I said the repeats you know at times can
during recombination when the homologous pair come together and then there is a recombination
then instead of homologous aligning exactly at the same site because the repeats and their
identical they can misalign As a result that could be an equal recombination
resulting duplication of a small segment of the gene or a deletion of the small segment
of the gene so this leads to you know loss of function or gain of function and depending
on how the gene affects the cell or the tissue You may have one disease or the other just
to give an example this particular gene is involved in a variety of functions in the
body and is very very critical for the neurons to survive So if you have some changes in the genes such
that the gene is not functional then that individual would develop a condition called
afro disease which is very very severe neuro degenerating disease The person to begin with
will be alright soon you would have problem in understanding memory cannot walk you will
have fixed what you call as epilepsy and invariably the person would die in about you know 25
years before that So that is really tells you how you know the
genome sequencing and all other technologies that evolved including this kind of developing
data bases helped us in one goal to understand the complexity of the genome and other functional
signatures which help anybody who need not be working on the genome but can you know
only working on a particular gene but it gives you every information which you can use to
understand the gene function So just to give another example this encode
uhhh project this is especially for people who are interesting in understanding the gene
function it is an encyclopedia of DNA elements It talks about data for example how for example
what are the transcriptions factors that bind to the fiber and of the gene and then for
example the chromatin modification and then prediction competition of prediction because
you know with the genome sequence you will have a large number of data bases Now there
are data mining software people have developed tools to understand to predict genes or signatures
and so on And this particular encode project really
really helped us to put together and analyse and get essence out of the genome that is
there and certainly you know you should go and have a look at it and that gives you more
information So it talks about for example the projects that are already there implemented
and what is the road map and so on and it talks about you know all the essays that are
you know put into this project so it is good to go on look into right And you can basically look into for example
the data the data could be for example the chip sequencing data meaning chromate immune
precipitation will talk about little later basically what you look into is that for example
is there any transcription factor that goes and binds to different elements in the genome
So what are the reasons that bind to because transcription factors are the one that you
know initiate transcription and uhhh in most of the cancers there is a global reprogramming
in the way the genes are expressed So if you can quickly look into what are the
transcription factors and where are they go and bind you will know for example what are
the genes that are up regulated or down regulated and for this people do what is called as you
know chromatic immune precipitation and and that data you know for example from uterus
of female adult you can see that and you know you can see it from the the nervous tissue
and so on So you can get the data for each tissue of the human and either a normal tissue
or from a cancerous cell so that really you know you can go on mine more and then get
more of understanding So that is uhhh one snapshot of this particular encode project So the other application because of the genome
sequence that has come is what is called as a vector based uhhh in this again a data base
dedicated to the genomic data of organisms that survives vectors say they themselves
do not cause any disease but they can help in transmitting the parasites and other microbes
to our body As a result you know we end up having a disease for example mosquito this
could be one for example malaria is another example and so on So you know this is again important area because
you want to understand the host of the parasites which carry them and how you know their genome
is organised and how do they function therefore the parasites are able to live there and reproduce
because more often what we get infected is a certain development level form of a particular
uhhh pathogenic right So if you can understand that and if you can you know do something
to their physiology probably we will be able to prevent or minimize the infection So again
its very very important there so that is something that there is come up and then it is not only
the human and parasites But even the plants are very very important
for us because we are dependent on the plant for our food and these are the primary producers
and which time you know that the land area that are being used for cultivation is shrinking
because there is a urbanisation So everywhere you see that there is a construction going
on as a result you know the the land area that is used earlier for farming has reduced
down Now what need to do the population is increasing
so you have a challenge with regard to how you are going to maximize the production of
the food grains therefore you can feed the population but from a much smaller land area
so you need to make plant that are much more resistant to pathogens at the same time give
more yield right at shorter duration right you know in the 40 days if you can get wheat
out of plant so rice out of plant So you reduce the time required and and give
more yield so that going to really help us so to understand the plant you know the genome
again there is a data base You can go there is a Braim data base again talks about all
the genome that have been sequenced which you can go on looking to for example the genome
browser which gives you the gene annotation and the diverse data and and then of course
the pathways involved in that and so on So again people work on plant science and look
into this data base to get more idea of it You have other data base there is a warm base
like ways its stores all the information with regard to the because is one of the powerful
models people used to understand the development and the genes regulations and many other aspects
So this you know data base is got all the information with regard to how many genes
are there where they are expressed what kind of function they confer and all the literature
whatever comes the outcome is added to that therefore one can you know have a look at
it So that is again is going to be of great help if you go on look into There is another model system FlyBase likewise
it is a very good genetic model to understand the gene functions and development and it
is not only talks about uhhh you know the drosophila genome and sequence but it also
talks about you know the relationship between the genes that are conserved across species
if you can recollect we discussed some time in last previous week about gene ontology
So the gene ontology is a data base is a dynamic data base which is being constantly updated
with the known or the understood functions of you know various genes The gene could be studied in Fly but we have
a you know similar gene in the human so whatever has been studied in the Fly that data has
getting to get into this data base so even if you want to now study human that you know
what has come from the Fly would help you in fact the pathways that are involved in
cancer for example you know what has been tested in you know drosophila it seems to
be very similar what has been found later in the humans So one of the ways by which people are trying
to use the Fly is to mimic a cancer that are happened in the humans for example I have
a cancer and my genome has been sequenced then that sequence information tells me that
what set of genes that are altered in a cancer Now the Fly being a very good model for genetics
studies so what one could do is within a month we can create all these combination that was
found in the gene combination that were found in my cancer We can create that in the Fly model and quickly
screen for drugs that are more effective in controlling this cancer and come back to me
for treatment so in this way I am going to give what is called as a personalised medicine
I am going to tailored the drug that are required to control my cancer depending on the kind
of genetic operation that took place in my body So you know the Fly is one such model
that really helps to realise what is called as a personalise medicine So that is where
even you know studying an insect really helps in understanding what happens in the human
and even to do a treatment so that is the one good thing about all these model system
and genomic information And finally we are going to show you one more
such data base called as Viral Bioinformatics resource centre again this is data base that
talks about all the viruses and their genome and their annotation and and all the you know
the publication that come out of this So that is the first lecture and we would
end here and then the next lecture we will look into how we sequenced the genome right

Danny Hutson

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