How Cells Become Specialized

Captions are on! Click the CC button at bottom right if you wish to turn them off. Follow us on Twitter (@AmoebaSisters) and Facebook! 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 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. So as a human, you started as a 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’s not going to result in different
specialized cells with different specialized functions because this cell division makes
identical cells. There’s something else that will be happening
for that. So let’s look at that in a bit of detail. We’re going to pause in this blastocyst
stage. This blastocyst contains stem cells. And these stem cells are amazing. See, they’re not differentiated yet. They’re not specialized. They are like blank slates. They don’t have a special structure. They don’t have any 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 don’t
have different DNA; they USE different parts of the DNA. Genes are regulated which means they can be
turned on and…off. That’s important to understand because that’s
a big part of how these stem cells are going to specialize. Stem cells will activate certain areas of
the DNA in their process of differentiating into certain 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, which
then can eventually be used to make specific proteins that can impact what a cell will
look like and what a cell will do. That means transcription factors have a major
role in determining which genes are expressed in a cell because a cell that is going to
become a skin cell is going to have different areas of genes expressed then a cell that
is going to be a …stomach cell. There are internal and external cues for stem
cells which can involve these transcription factors. Examples? Ok 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 originate from it. 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…or 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, or bone marrow just to name a few. These are often called somatic stem cells. To give some relevance to this: it’s likely
you have 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 donor 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 body
cells but not as many as the embryonic stem cells. So, after talking about these stem cells,
why the heavy focus on these stem cells 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 helped 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 stems cells. The ethical issue is significant because the
extraction of embryonic stem cells results in the demise of the embryo. A point consistently debated is the potential
benefits offered in 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 come from that person will carry the risk of organ or tissue
rejection, as you can get in 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 what we call
induced pluripotent stem cells (iPS). That means a person’s own stem cells potentially
could then 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 decrease 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—all of our 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!


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