Developmental Biology

Week Sixteen: Working with bubbles is more than just fun

2013-04-29T18:44:34Z

Today in lab, we made a mixture consisting of Dawn soap, water, and glycerine in order to play with bubbles. Although this was fun, it actually has some application to developmental biology. In fact, many biologists have written books about the math behind soap bubble forms that can be related to cellular architectures (i.e. epithelial sheet or a blastula).

Although it was a lot harder to manipulate the bubbles than I thought, I was able to make some pretty cool formations. The first bubble formation that I was able to make is similar to the blastoderm with the blastocoel and blastoderm layer (see image). Although I was only able to make a few bubbles line up, you can still see how the bubbles attach to the end of another bubble in order to form a lining around the center. However, this is also some asymmetry with the bubbles which was hard to avoid.

The second bubble formation that I was able to make is a little harder to describe in relation to biology. This bubble formation kind of resembles the gastrulation of the blastula to form the gastrula where the outside layer folds into the center. However, you can see the differences in the last image below of the gastrula. Gastrulation is the process that forms the three germ layers known as the ectoderm, endoderm, and mesoderm. After this stage, the organs will being to develop during organogenesis.

Week Fifteen: Neurogenesis and developmental consequences

2013-04-24T19:40:46Z

In class today, we discussed the article "Evo-Devo and Brain Scaling: Candidate Developmental Mechanisms for Variation and Constancy in Vertebrate Brain Evolution" by Christine J. Charvet, Georg F. Striedter, and Barbara L. Finlay (2011). One of the most interesting concepts was how the delay in neurogenesis can impact development and the function of an animal.

Specifically, neurogenesis in the retina and the isocortex was explored amongst various animals. When looking at the retina, the nocturnal owl monkey and the diurnal capuchin monkey was compared. During development, the highest amount of neurogenesis is delayed in the owl monkey in comparison to the capuchin monkey. This is significant due to the time when rods and cones are developed. Early in development, cones are the focus, while later development consists of rod creation. Therefore, the neurogenesis in the owl monkey is delayed which results in larger amount of rod production. Rods are specialized for light and cones are specialized for color. The owl monkey, with a higher concentration of rods, is better able to see in the dark and be nocturnal.

Next, the paper discussed the differences in isocortex development among primates and rodents. The isocortex is made up of six layers (I-VI), which all grow during different times (i.e. layer VI develops before layer I). The neurogenesis of the isocortex is delayed in primates in comparison to rats. Therefore, the later layers (II-III) are disproportionately enlarged relative to the other layers in the primates due to a delay in neurogenesis.

It is interesting how the onset or offset of neurogenesis can have such significant impacts on the development and function of certain parts of organisms.

Week Fourteen: Drosophila Mating Behavior

2013-04-15T18:32:28Z

After much struggle, we are finally done with the drosophila development lab. Our assignment was to pick something interesting during drosophila development (i.e. mating to pupae hatching) and record it using a Leica Wild M3C Scope and a PixieLINK camera. My lab partner and I put two flies (male and female) into a small petri dish with a damp KIMTECH wipe around the sides. Although this proved to be troublesome during recording, it allowed a moist environment for the flies to thrive.

During drosophila mating, males exhibit a unique courtship behavior in order to engage the female. Initially, the male circled the female in order to orient himself to her. Unless male flies are desperate, they will only engage in copulation with a virgin female fly. After orienting himself to the female, he began to flicker his wings at her. Then, the male chased the female around the petri dish, which was hard to follow in order to capture the video. The male, then, began to tap the female when he got close enough to her. It appeared as though the male also engaged in some other mating behaviors but it was hard to tell. The male attempted to copulate with the female but there was no clear copulation seen.

An interesting note: our female displayed mutant (white) eyes and very short wings. We were not sure if her wings were short because she was young or if she also displayed a mutant wing type, as well.

After many hours attempting to get perfect timing for certain development behaviors of fruit flies, we finally succeeded! Attached below are three videos that demonstrate our results as described above. Enjoy!

Fruit Fly Mating Behavior 1: iPhone Capture

Fruit Fly Mating Behavior 2

Fruit Fly Mating Behavior 3

Fruit Fly Mating Behavior

Week Thirteen: Maternal and Zygotic

2013-04-08T14:33:23Z

Today in class, we reviewed drosophila development and continued with vertebrate development. One of the most interesting concepts that we discussed was the role of maternal and zygotic sources for development. Although we often think that vertebrates (especially mammals and humans) are more 'nurturing' and 'motherly' than invertebrates, such as the fruit fly, our preconceived notions may be false in some manners.

During development, drosophila embryos have pre-patterning from their mothers that determines much of their development and organization. So many components of the fruit fly are fixed before any fertilization or division. Although this may seem odd, it serves much evolutionary purpose in saving time in order to exploit limited food sources.

In comparison, vertebrates, especially mammals, have much less pre-patterning from their mothers that determines the organization in development. In fact, maternal influences are minimal until after the organism is born. Due to the complexity of vertebral development, it takes much longer for the embryo to grow into a full-term fetus. Therefore, it would not be evolutionarily advantageous if a human baby developed in 8 months versus 9 months so there is nothing to drive this type of evolution. However, it is very advantageous for fruit flies to develop faster in order to survive.

Week Twelve: Why is this beautiful?

2013-04-04T00:41:33Z

In class today, we continued to discuss Endless Forms Most Beautiful by Sean B. Carroll. Specifically, we dove into chapters 8 and 9 which pertain to butterfly wing spots and zebra stripes. Although Carroll has received much criticism for focusing so much on these two topics, we discussed why this information might be important and, more importantly to some, why it might be beautiful.

When applying for research funds, many organizations ask you to provide an explanation of why your research is important and how it can be applied to the well-being of humans. Although this may seem sort of ignorant to some, it is the main focus of much of society. In Carroll's book, butterfly wing spots and zebra stripes may seem unimportant, we discussed many reasons as to why it is important and applicable to the human population. For example, the main idea behind the unique patterns of animals is the ability of genetic switches to control expression in different body parts. While this may result in a spot on a butterfly wing, it could also apply to male baldness patterns or even more compelling mutations.

Although it is necessary to describe the importance in order to satisfy research funding organizations and much of society, many others are far more baffled with the idea that biologists like to research such things. So, a better question for these folks to answer would be, why is this beautiful? Despite the incredible patterns that zebra stripes and butterfly spots can display, there are many more intriguing aspects of such research. For example, when looking at two butterflies, they may display nearly the same pattern. However, they may be completely separate species of butterflies. So, how did they develop this patterning and what is it's significance? Only research will tell us.

As a biologist, it is oftentimes hard to explain to people why something can be equally important and intriguing if it does not have a direct connection to the human species. In order to continue research in peace or fuel motivation for research, it might be useful to think about why is this important? and why is this beautiful? Or sometimes, in the words of a wise student, it might be useful to respond by saying, 'In the future, we might want to learn how to become pigmented in patterns like the butterfly,' and that will probably be enough.

Week Eleven: Insect Wing Specialization and Hox Genes

2013-03-30T15:58:40Z

In order to elaborate further on the differentiation of species and organisms within species after the phylotypic stage and its relation to Hox genes, I thought it might be useful to discuss the evolution of wing number and form. In Sean B. Carroll's book, Endless Forms Most Beautiful, he describes this process by using the gill-to-wing theory. The gill-to-wing theory has much evidence that supports the evolution from crustacean gill branches to insect wings. Of course, there are many transitional evolutionary steps that this change required. For example, a mayfly nymph, a primitive winged adult, and a modern lepidopteran all have very different types and numbers of wings. Specifically, the mayfly nymph does not have any wings on T1, whereas the primitive winged adult has reduced T1 structures and no wings on the abdomen.

So, how does this differentiation of wing number and type occur across these species? According to Carroll, it is much related to my previous post that related this specilaization to Hox genes. In fact, the addition of more Hox gene binding sites allowed for the promotion and differentiation of wing development. Therefore, it is evident that Hox genes and their binding sites play a major role in determining the structures and forms of unique species.

Week Ten: Phylotypic Stage

2013-03-29T23:29:53Z

In class this week, we discussed the idea of phylotypic stage. In many previous courses, including biology and psychology courses, I was always taught that early embryos of separate species look extremely similar. While this is partly true, the artistic representation (Image 1) that has always been displayed in class is exaggerated. The 'partly true' portion of this phylotypic stage, however, is quite interesting to me. You can see a realistic version of the phylotypic stage in Image 2.

During the phylotypic stage, structures are similar across very different species including the notochord, somites, and neural tube. So, how do such similar structures develop into such unique organisms? Well, it is theorized that as the phylotypic stage progresses, Hox genes are expressed which specify positional identity. The pattern of Hox gene expression is very different across species, which allows for specialized body plans and unique organisms. Therefore, the phylotypic stage tapers off as species become less similar, much like the hourglass model seen in Image 3.

Week Nine: Drosophila Development

2013-03-11T20:29:48Z

For our next lab, we will be taking a progressive set of pictures that will be arranged into a movie. The theme: something interesting in drosophila development! I thought it would be helpful to look up the development of drosophila in order to get a better idea of what I want to focus on (all dependent factors aside. i.e. time). I realize that while I might like a certain part of development more than another, it might be near impossible to capture that moment in time. I think it would be interesting to look at the gradual development from a pupa to an adult, giving rise to legs and wings. However, since they encapsulate themselves, it may be impossible to see this transformation. Therefore, I would like to try to see when the adult drosophila emerges from the pupa into a fully formed organism with wings and all. Although it may be hard to identify when the transformed adult will emerge from the pupa, I think I will be able to monitor it enough to get a good idea with the help of Professor Myers. I am hoping that it will look much like the video linked below! Drosophila Video- Pupa to Adult

Week Eight: Gynandromorphy Post Response

2013-03-06T02:03:37Z

This is a response/expansion to a post written about gynandromorphy by a student in my developmental biology class, Miles. It may be useful to read this post prior to reading the following post.

Gynandromorphy occurs when an organism displays both female (gyne) and male (andro) physical characteristics (morph) due to sexual dimorphism. In the photo of the gynandromorph lobster, it appears as though it is bilaterally symmetrical. However, this is not always the case. In fact, some gynandromorph organisms display a mosaic pattern in which the two sexes are not differentiated as clearly. The pattern of gynandromorphy is dependent on the determination pattern of cells during division. This disorder is a result of an early event in development, specifically mitosis, which does not split the sex chromosomes in a typical manner. Although I was curious as to whether these organisms can reproduce, I couldn't find any information on the topic. However, many articles related this disorder to hermaphrodites and intersex individuals of the human species. In these cases, most individuals are sterile as a result of their disorder. With most individuals, the reproductive organs are incomplete and can, therefore, not reproduce. It may be possible that an individual with gynandromorphy or hermaphroditism with complete organs could reproduce but I do not know nearly enough about the subject to speculate.

Week Seven: When Evo meets Devo

2013-03-06T01:07:21Z

Learning about genes, proteins, switches, 'genetic tool kits,' and the like has been particularly interesting. However, the part of this course that has been distinctively exciting is how these aspect of development are connected to evolution. As described in Endless Forms Most Beautiful by Sean B. Carroll, wing development sheds some light on powerful evidence of evolutionary development. From gills to wings, a few proteins have been identified as necessary components for this type of development. Specifically, Apterous and Nubbin have been found to be selectively expressed in areas where wing and gill development take place (i.e. the respiratory lobe in crustaceans).

It is evident that these homologous parts are significant in the study of evolutionary development. In fact, this particular case can tell us a lot about evolution of many species, including humans. Relating to Hox proteins and genetic switches, the repression or expression of specific products or parts, such as wings of insects, can be traced back. These genetic switches were involved in the development of signature sequences for Hox proteins that can result in either the 'turning on' or 'turning off' of particular segments. Therefore, differences in wing expression among separate species can be traced back to common Hox protein and the expression or repression of sequences and proteins.

Week Six: Roux and Regulation

2013-02-18T18:11:06Z

For our take-home exam, one of the questions asked about mosaicism and regulation and the differences between the two. I was particularly interested with each mechanism's relation to cell-to-cell interactions and how these interactions imply how these mechanisms exist in the environment naturally.

Mosaicism is the mechanism in which a cell's fate is predetermined by factors it receives during each cleavage. This principle suggests that the mosaic mechanism would not require cell-to-cell interactions. More interestingly, no truly mosaic embryos are known to exist in the environment. Therefore, there must be some other mechanism that is used in order for cell differentiation and embryo development.

Regulation is the mechanism in which an embryo is able to continue developing normally regardless of any changes or destruction. In order to detect these changes, there must be some form of cell-to-cell interactions.

Although there are some organisms that develop as if there is no cell-to-cell interaction and with a predetermined cell fate, it is evident that this is not the only mechanism for development. However, it is important to note an experiment done by Wilhelm Roux that suggested mosaicism as a basis. While studying fertilized frog embryos, Roux destroyed one of the two cells after the first cleavage. The remaining cell developed into only half of an embryo. Therefore, he concluded that mosaicism must be the basis of development for this organism. With this experiment, it only seemed logical that mosaicism was a useful mechanism.

So, if there are no purely mosaic embryos in the environment, what type of mechanism other than mosaicism takes place within a frog? With Roux's experiment, it seems as though mosaicism is a clear answer for this embryonic formation. However, this is only the result because Roux left the killed cell attached, but the embryo did not recognize the cell as being nonfunctional. If the killed cell had been removed, the embryo would have gone through regulation in which it would have developed into a smaller, but normal embryo.

Therefore, regulation is a key mechanism in development. However, with the information presented in class and my own critical thinking, it was hard to come up with this as the answer. Now that I finished my take-home exam, I decided to look up the real 'best' answer for development and it seems as though regulation is it!

Week Five: The Six-Fingered Man

2013-02-13T02:32:52Z

Inigo Montoya: "I do not mean to pry, but you don't by any chance happen to have six fingers on your right hand?"
Man in Black: "Do you always begin conversations this way?"

In The Princess Bride (1987), a character named Inigo searches for a six-fingered man who had killed his father when he was a young boy. Although it is supposed to be comical, this variation is not as rare as one may think. In fact, according to the book, Endless Forms Most Beautiful by Sean B. Carroll, about 5 to 17 births out of 10,000 display this variation, known as polydactyly. Other well-known individuals who were born with polydactyly are Anne Boleyn, wife of King Henry VIII, and Antonio Alfonseca, a pitcher for the Marlins. However, it is important to note that this variation has a range of appearances including an extra flap or piece of skin on the side of the hand, individual bones, or duplication of the nail. This mutation has also been seen throughout many vertebrates including mice and chickens.

How might one obtain this variation? Commonly, polydactyly is either inherited or induced experimentally. In fact, scientists believe that there are similarities in the manner of developing this mutation between chickens and humans. However, most advances within this area were made when studying the fruit fly.

While Carroll terms these mutations as 'monsters' or 'mutants,' these variations have incredibly useful suggestions for the rules and process of development. This information can be used to describe the formation of all bodies and body parts of humans and other animals alike. By inducing experimental changes and observing the physical transformations in an organism, scientists are able to track certain genes and investigate how a change could lead to large (or no) effects in a structure.

Week Four: Chick Development

2013-02-07T19:06:28Z

For lab this week, we were instructed to document certain stages of the development of chicken embryos. Before I get started, I decided to learn a little more about the development of this organism. I think this acquired knowledge might help me in the process of capturing significant stages and structures when conducting the lab.

Once an egg is fertilized by a sperm, the embryo will begin to develop after about five hours, forming the zygote. It will then begin cell division and eventually change into the blastoderm. This stage is comprised of eight cells which will develop into 256 cells after just four hours. The embryo, then, differentiates two layers known as the endoderm and ectoderm. The endoderm will eventually turn into the respiratory and digestive systems, as well as secretory organs. the ectoderm will produce the nervous system, sections of the eyes, the feathers, beak, skin, and claws. Eventually, a third layer will develop known as the mesoderm. This layer is important for producing the skeleton, muscles, circulatory system, reproductive organs, and excretory system.

At day one, the embryonic tissue begins to appear; day three, the heart beats; day eight, feather tracks are seen; day thirteen, the body is slightly covered in feathers; and day twenty, the embryo becomes a chick. Before a human embryo even begins to have a heart beat, the chick embryo is fully developed and ready to hatch.

Below is an image of a chick embryo at 96 hours. As you can see, many of the organs of the chick are distinguishable.

Reference: http://www.poultryhub.org/physiology/body-systems/embryology-of-the-chicken/

Week Three: Drosophilia and Other Embryo in Development

2013-01-28T18:39:49Z

In the first two weeks of developmental biology lab, we have been able to use a Leica DMLB research scope. Although it was intimidating at first with many more knobs, buttons, and value than I am used, I soon learned that it was much less complicated than I anticipated. Featured below are two of the images that I captured using the a camera connected to the camera tube on the scope. Subsequently, the links below the two images are photoshop-edited versions in which I enhanced by adjusting contrast and sharpness, as well as adding a scale bar. The objective lens used was 5x/ 0.12.

embryoinsitusec2edited.psd

The first image (above) is an illustration of an embryo in situ (in position). Unfortunately, the label of the slide did not identify an of the specificity of the embryo type or time of development. However, you are able to see a pattern of cells that. hopefully, I will be able to identify more specifically as the course progresses. The second image (link) is a more clear representation of the development of the embryo. With the help of photoshop and the ability to adjust the contrast and sharpness, I was able to create a better quality picture.

drosophiliadevelopingedited.psd

The second image (above) is an illustration of a drosophilia embryo. However, the specifics of development are minimal. On the slide information, it stated 'Drosophilia development.' The link below the image is an edited version using a photoshop program. I edited it by adjusting the contrast and sharpness of the image, as well as adding a scale bar. Although the Leica DMLB scope produces fantastic images, the camera seemed to decrease the quality of the image. Therefore, the ability to edit the images using a photoshop program has great advantages.

Week Two: Epigenesis- Nature and Nurture

2013-01-26T00:18:16Z

As a student with a large psychology and biology background, I am continuously fascinated with how much the two subjects overlap and complement one another. Recently, I have been interested in the topic of epigenesis,which occurs when events change how our genes are expressed. Differing from my previous understanding, the presence of a gene does not necessarily determine a particular trait, rather, the trait only occurs if the expression of that gene takes place. Therefore, environmental events, such as diet, stress, and drugs, can actually result in phenotypic and behavioral changes. Although many individuals now agree that both environment and biology play critical roles in determinism, this process further supports the relationship.

Specifically relating to psychology and biology is the topic of neurobehavioral epigenesis. This subject may be an explanation for the differences in development of mental disorders and other behaviors in individuals with similar backgrounds and experiences. Even though the two individuals have experienced virtually the same events, one may exhibit significant stress or trauma related to an event. Also, it is helpful in the prevention of mental disorders. If a person has a lower genetic threshold for developing an abnormal behavior such as alcoholism or depression, it may be useful to educate the individual and, possibly, decrease the chances of a particular gene from being expressed.