Differential Expression, Morphogens, and Pattern Formation

by Jason Amores Sumpter
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Hello, everyone. In this lesson, we're going to be talking about differential gene expression. Okay, so what is differential? Gene expression Basically differential expression is going to result in multicellular organisms having different types of cells. Obviously you have different types of cells, right? You have skin cells, you have liver cells, you have eyeball cells. You have many different types of cells that do different jobs. But how do they do different jobs if they all possess the same genetic makeup? Well, that's where differential expression is going to come in. So differential expression is when they're different patterns off gene expression and this is going to lead to different cell types. So we're gonna have different types of cells Now, remember, the genetic makeup of every cell in your body is exactly the same. They all have the same DNA, except for maybe a couple mutations between different cells. They should all be exactly the same. So how is this going to happen? What? We're going to have chemical signals inside of our bodies and ourselves that cause differential gene expression. What this means is we're gonna have signals in our body that tell certain genes in certain cells to turn on and to turn off. So you're gonna have some genes that skin cells will never express. And some genes that skin cells will Onley express. So there are genes unique to each type of cell in your body in your genetic makeup and which genes certain cells air going to express is dependent on their chemical signals that they are given. And this gene expression can be modulated or changed or regulated in many different ways. Which genes are being expressed can be changed or determined by many different factors, including transcription a LRA, Gye Lei Shen. This is going to be which genes are transcribed and which ones are not. In certain cells, some genes will be silenced. They won't be allowed to transcribe, and in some cells they will be expressed. They will be told to transcribe into em Arna. Now there's also RNA splicing so this can create certain Marianas, which can create certain FINA types, certain types of proteins. Depending on how that RNA is built now, you can also have translational regulation. Translational regulation is actually determining which Marna is allowed to become a protein, or how many of a certain genes are allowed to become a protein, so this is going to regulate the phenotype off the proteins and of the sell by regulating translation. So this is going to regulate the expression of that cell, and we also have post translational modification. So a protein is made, it is translated, and then it is modified to do a particular job that that particular cell type might utilize these processes air all going to determine differential expression. All of these processes air going to be utilized to give cells unique gene expression and unique FINA types. Remember, gene expression is thief phenotype or the characteristics that air created from the genes that are being expressed? And there are many different ways to modify that expression, including thes four ways, and that's going to create a unique phenotype for each cell type. So also, regulatory factors like transcription factors are going to be utilized to influence which genes are basically turned on and turned off. Now remember, very, very important. I know I already talked about this, but remember that all cells are genetically equivalent. They all have the same genes. They just use different methods to have their unique FINA types. Now we have a visual representation right here of what that might look like. So let's say that these two different cells come from the same multicellular organism, so they're from the same organism, but they obviously look incredibly different, and they probably have very different jobs. Now let's say that this organism on Lee has these three genes I know Unlikely. But let's just go with it for simplification. So let's say it on. Lee has thes three genes, and as you can see, thes, two different cells in these multicellular organisms are expressing these genes differently. You can see that this first cell is expressing Gene a twofold. Let's just say it's expressing gene a two fold, and it's not expressing Jean B whatsoever. And it's expressing Jean C one fold. So obviously it has this particular phenotype because it expressed these genes this way. Perhaps this particular gene be was not transcribed it all. Maybe it was silenced and told not to transcribe. So no Amarna was made whatsoever from this gene. But then let's say that ah lot of Amarna was made for Gene A and a lot of it was translated, so there were many gene products created for Gene A. And maybe only a little bit of Jean C was translated and transcribed, so not as many gene products were made. Things is all going to be dealing with translational and transcription ALS regulation. Now let's look at the other cell. We can see that the other cell did not express Gene a whatsoever. So perhaps Jean A is not transcribed. Maybe it is silenced like the other cell did with Jean B. But we can see the gene B in the second cell is expressed threefold. So this is a really express gene. Maybe it's transcribed a lot. A lot of Marina is created, it is enhanced, and it is translated very quickly and very rapidly. Now we can also see that it does express Jean C two fold as well. This is going to be regulated by its transcription and translation of these genes, and these two different ways that they do these processes off transcription, translation and all these other modulating processes is going to give them their unique phenotype. So this is how we get different cell types now. This is going to lead into the topic of pattern formation. Pattern formation is the complex organization of the different cell fates in your body over space and time, and this is going to be controlled by genes. So basically, pattern formation is dealing with how you're different. Cell types are made, how your tissues and organs are made, and when that happens and where that happens. So, for example, does it happen in utero when the fetus is being created? Or does it happen during puberty? When you're having hormonal changes and different parts of your body are changing their different times and there are different spaces or locations in the body, that pattern formation is happening, and this is all due to differential expression off the genes, which genes are expressed and which ones are not. Now how you develop patterns, how you develop your body organization is greatly controlled by these very important molecules called Morfogen. Morfogen are molecules used to indicate sell position. They indicate sell position via concentration. Grady INTs during pattern formation. What's another word for pattern formation? Another word for formation or pattern formation is more of a genesis, and this is going to be why the name Morfogen comes about because they help with the process of Morphy, Genesis or the building and developing off the body of the organism or the patterns in the organism. These Morfogen zehr very important molecules. Now, I have some examples down here of how these Morfogen zehr gonna work because I know that the concept can be a little bit confusing. So more virgins are utilizing a concentration Grady int. And that Grady int is highest around the cells that admit that particular protein or that particular molecule and cells respond to the particular concentration that they have, whether it's high, medium or low, that cell will recognize Hey, I'm getting a low concentration of this Morfogen. That means I need to do this job and this is based on their location in the body. And this is going to create the specific responses which create specific cell types depending on the concentration of the Morfogen that these cells get is going to tell them the cells, location in the body and what they're supposed to become, what type of tissue and organ they're going to become and basically what job they're going to do. And very important, Morfogen are going to set up the body axes. So your middle, What's top? What's bottom? What's left? What's right? All of this is gonna be determined by these Morfogen molecules. There are a ton of different Morfogen molecules which you will learn about in more advanced biology classes and anatomy classes. But some examples for mammals are retinoic acid. BMP my favorite sonic hedgehog. Yes, funny name, but it is a Morfogen and it is utilized to determine the placement of your fingers in your hand, which is really neat. Now, this example down here is going to be of Drosophila or fruit flies. And I do have two examples of Morfogen at work. The first one that we're going to be looking at is by Coid and the second one we're gonna be looking at is Nano's And this these air just names of the particular Morfogen. Now this is going to be the egg off a Drosophila or excuse me. The zygote of a Drosophila that will become a fruit fly and by Coid and Nano's are utilized to set up the head and the abdomen. So by Coid is at its highest concentration. Oh, sorry about that highest concentration in the head region off the zygote. The region of the zygote that will become the head off the Drosophila fruit fly is gonna have the highest concentration of bike oId, and then by coid, is going to defuse through the zygote. So the lowest concentration off the bike oId Morfogen, is going to be at the abdomen or the tail region off this fruit fly. Now we also have Nano's. Nano's is gonna work in the exact opposite method. Nano's is gonna have its high concentration towards the abdomen region or the tail region off this particular fruit fly. So there's gonna be really high concentration in the cells that will be the tail and then it's going to defuse towards the head so the heads can have really low concentrations. And these two Morfogen working together tell the cells in the Saigo where their position is, whether they're closer to the head or closer to the tail. And this is when the fruit fly is developing. It's obviously not fully developed, but it is developing, and you can see the regions of the head, the thorax and the abdomen, and you can see these different regions with different colors. And this is to represent the different areas of the body that air determined by different Morfogen. You have more than just to chemical signals. There are tons of Morfogen that air utilized to determine the different locations of the body so that the cells know their placement and know their job. And you can see that in this example here, with all these different colors representing the different locations of the different Morfogen concentrations in the different cell types. And that is going to be how the body develops via differential expression and pattern formation. Now let's go on to our next topic.