How Cells Become Specialized [Featuring Stem Cells]

We've mentioned a lot about specialized cells. Specialized plant cells, specialized animal cells, so many kinds of specialized cells it's going to get a bit crowded here. But have you ever wondered, how do they get specialized? How does a neuron or a muscle cell in your body have the structure and function they have? I mean, can you imagine if they had to switch jobs for a day? That wouldn't go so well. They're so specialized for the function they perform. Well, this video is going to talk about how cells differentiate into other cells, which basically means how cells become specialized. Remember that many multicellular organisms, like a plant or you, well, these organisms come from a fertilized egg cell. Let's take a look at a human fertilized egg, otherwise known as a zygote. Well, that zygote divides to make more cells. And more cells. Oh, look, it's a morula. And more cells. Oh, look, it's a blastocyst now. You know, the problem is, if the cells just keep dividing, if you remember from our mitosis video, that makes identical cells. Well, that's great for growth. And so dividing is definitely going to happen. But that alone is not going to result in different specialized cells with different specialized functions. There's something else that will be happening for that. So let's take a look at that in a bit of detail. We're going to pause here. The blastocyst. Notice it has stem cells. And these stem cells, they're amazing. See, they're not differentiated yet. They're not specialized. They're like blank slates. They don't have a special structure. They don't have a special job. They can become any type of body cell. Now, a reminder about body cells in your body. They all, with a few exceptions, contain all of your DNA. So neurons and muscle cells in your body, they don't have different DNA. They use different parts of your DNA. Genes are regulated, which means the genes can be turned on and off. It's important to understand because that's a big part of how these stem cells are going to specialize. Stem cells will activate certain genes in the process of differentiating into different types of cells. Transcription factors are major key players here. They're typically, but not always, proteins, and they determine which areas of the DNA code will get transcribed into mRNA. That mRNA can eventually be used to make specific proteins that can impact what a cell is going to look like and what a cell is going to do. That means transcription factors have a major role in determining which genes are expressed in a cell. Because a cell that's going to become a skin cell is going to have different areas of genes expressed than a cell that's going to become a stomach cell. There are both internal and external cues for stem cells, which can involve these transcription factors. Examples? Okay, an example of an internal cue could be transcription factors present in the cytoplasm of the original starting zygote cell, which will eventually be present in the cells that come from it. Now, the specific location of the stem cell within the developing embryo can matter because the transcription factors available in different areas of the developing embryo can differ in quantity and type, which could impact what a stem cell differentiates into. External cues could involve cell signaling from other cells next to it. External cues can even be environmental effects like temperature. There's still a lot of research in this area and we can't wait to see what scientists discover about this in the next decade. So stem cells are the unspecialized, undifferentiated cells that can become other cells in your body. But not all stem cells are found in a developing embryo. Stem cells can also be found in your body as well, like your muscle, skin, liver, bone marrow, just to name a few. These are often called somatic stem cells. To give some relevance to this, it's likely you've heard of bone marrow transplants before. Well, bone marrow transplants actually involve transplanting a portion of healthy bone marrow, which does contain bone marrow stem cells, with the idea that those donors' stem cells can help regenerate different types of blood cells, since bone marrow is like a blood cell-making machine. It contains stem cells that differentiate into different types of blood cells. Many, but not all, of the somatic stem cells that are found in your body are considered to be multipotent. That means they can become many types of cells, but not as many as the embryonic stem cells. So after talking about these stem cells, why the heavy focus on them right now in research? Well, one reason, of many, is that these cells have the ability to differentiate into other cells, and therefore, they could be used to help regenerate organs or tissues that are damaged from a disease or an accident. There are two important issues to consider, however. One is the ethical issue, especially if considering embryonic stem cells. The ethical issue is significant because the extraction of embryonic stem cells results in the demise of the One point consistently debated is the potential benefits offered in embryonic stem cell research versus the onset of personhood of human embryos. A second issue is that organ or tissue developed from stem cells that didn't originate from that person will carry the risk of organ or tissue rejection, possibly similar to what you could get with donated organs or tissue. But here's something promising. Some research shows that somatic stem cells from your own body may actually be able to develop into more types of cells than what people first thought. In fact, it was discovered that some somatic stem cells can be induced to go back into a pluripotent state. They're called induced pluripotent stem cells. That means a person's own somatic stem cells from their own body could potentially be induced into a pluripotent state with the potential that they could differentiate into tissues or organs that the person may need. Theoretically, this could be an alternative to waiting for an organ or tissue donor, as well as lower the chances for organ tissue rejection, since the organ or tissue would have originated from the person's own cells. We encourage you to keep up with the topic of stem cells, to stay educated on this topic. The understanding of these undifferentiated cells is likely to advance in the near future. Well, that's it for the amoeba sisters, and we remind you to stay curious.