Is the default brain female?
During embryonic development and specialization, is there a default brain gender? Is the brain feminine or masculine in the absence of specific inhibitors or activators? Does this have anything to do with gender identity?
These are perplexing questions nonetheless. Recently, using a mouse model, researchers at the University of Maryland addressed some of these questions. They noticed that during embryological development as well as shortly after birth the degree of DNA methylation by DNA methyltransferases dictated the gender sexual copulation characteristics. When they knockout one of these enzymes, Dnmt, the female mouse begins to express male sexual behavior. It appears that the methylation of masculinizing gene(s) results in feminine sexual behavior whereas male hormones block the methylation events so that these masculinizing genes are expressed. The genes in question do contain many CpG islands that can be methylated/demethylated. We have discussed the effects of DNA methylation on transciption and gene expression in several classes, including Biochemistry, Neurochemistry, and especially Chemistry of Cancer.
What does this signify? Does it have anything to do with gender identity?
The link to the original article in Nature Neuroscience can be found below:
Brain Feminization Requires Active Repression of Masculinization via DNA Methylation
These are perplexing questions nonetheless. Recently, using a mouse model, researchers at the University of Maryland addressed some of these questions. They noticed that during embryological development as well as shortly after birth the degree of DNA methylation by DNA methyltransferases dictated the gender sexual copulation characteristics. When they knockout one of these enzymes, Dnmt, the female mouse begins to express male sexual behavior. It appears that the methylation of masculinizing gene(s) results in feminine sexual behavior whereas male hormones block the methylation events so that these masculinizing genes are expressed. The genes in question do contain many CpG islands that can be methylated/demethylated. We have discussed the effects of DNA methylation on transciption and gene expression in several classes, including Biochemistry, Neurochemistry, and especially Chemistry of Cancer.
What does this signify? Does it have anything to do with gender identity?
The link to the original article in Nature Neuroscience can be found below:
Brain Feminization Requires Active Repression of Masculinization via DNA Methylation
This article says that for a brain to "feminize," methylation has to occur in order to repress the "masculine" brain. This indicates that the default brain (if there is such a thing) is masculine. This is fascinating from a Christian perspective, as we know that Adam was originally created as a male. Eve, the woman, was made from the man. Postulating from the information in this article, perhaps Eve was not only made from Adam's side, but her brain was also derived from methylation of a male brain? This would seem to be supported by both scripture and science. Men could see this as an opportunity to brag that their brains were the original design, but I think females could also argue that they got the new and improved male brain version 2.0.
ReplyDeleteInterestingly enough, the gender of many reptile hatchlings (chelonians, crocadilians, and some lizards) is temperature-dependent. There are two models of temperature-dependent sex determination in reptiles. In the first model, the percentage of males that hatch decreases as the incubation temperature decreases. This method is found in many chelonians. Some lizards are dependent upon another model, where the percentage of males is highest at a certain temperature range and decreases sharply when the incubation temperature is higher or lower than the ideal range. Intriguingly, this implies that males are produced far more often than females at the ideal or "normal" temperature range. Perhaps this implies that males are the "default" gender for these reptiles. Biologically, it would be interesting to research what the significance of this might be.
Michael,
DeleteInteresting analogy...version 2.0
It makes sense that certain sex hormones influence sexual behavior. However, it would be interesting to what degree these genes and hormones affect psychosocial behavior. I remember learning about CpG islands and how there methylation can reduce transcription rates resulting in cancer or other diseases. It is interesting to see the role they have in development as well. I wonder if this information will lead to the discovery of a genetic basis for gender confusion disorders or homosexuality. I found it interesting that you said the brain was destined to be female. I imagined the brain as destined to be male after reading the article since constant suppression of masculine genes are required to produce the female phenotype.
ReplyDeleteI agree with Mike. Sex hormones play a large role in the overall sexual behavior of an individual, but to what extent? Where is the line drawn between characteristics and character. Individuals can behave with similar traits of the opposite gender. For instance, females who act tougher, more independent, and adventurous may be labeled a "tom boy" because their behavior is more geared to the male sex. That does not define her identity as a male character, rather her characteristics. Depending on the force of these hormones is can be observed that gender identity is questioned. Such confusion can lead to a variety of psychological struggles later on in life. It would be interesting to see if these hormones can be regulated in pre-existing gender identity cases. A discovery like this could ease a multitude of confused and tortured individuals struggling with this disorder.
ReplyDeleteThis is such an interesting phenomenon and I agree with Michael, from a Biblical perspective this topic is even more fascinating. If the male brain preceded the female brain, one could in fact argue that our Divine Creator needed a rough draft before creating the final masterpiece. In addition, God probably saw how overwhelmed Adam was in the garden when he was given the task to name all of the animals and He knew that a feminine brain capable of multitasking should be created.
ReplyDeleteIn Chemistry of Cancer we spent a great deal of time talking about CpG islands and upregulated vs. deregulated methylation and their role in carcinogenesis. It is very interesting to see that these things have a role in gender as well. I am curious to know if these findings may point to answers for those with gender identity problems. If more research is done on this topic, society may actually find answers to many questions raised by those with gender identity issues. Many question whether this confusion is programmed into a person, or whether it comes about by upbringing and environmental factors. This data may be able to begin to point to gender confusion being nature rather than nurture.
ReplyDeleteThis is the kind of topic that many people have been searching for to fight arguments. It's extremely interesting to think about especially as I've learned about CpG islands in Chem of Cancer and it cool to see their other involvements. It sounds like it could almost be a "which came first topic". Does the hormones block methylation first, or are the genes methylated first? This is where the ethical questions come in concerning gender identity. I still feel as though there is a lot more behind it that comes in to play, but we will have to wait until more research as been conducted.
ReplyDeleteWe briefly discussed this type of “male vs. female” differentiation in Embryology with respect to gonad development. Every fetus will become a female until male sex hormones present, causing differentiation. It seems that this is the same way that the brain differentiates into the “male” and “female” brain. The article states that brain feminization is independent of the ovaries; however, brain masculinization is not independent of the fetal testis. In fact, gonadal steroids generated by the fetal testis cause this differentiation in the “male” brain.
ReplyDeleteIt is amazing that such “small” changes can cause such drastic effects. DNA methylation plays a large role in many processes, such as activation and repression of many genes. By adding a methyl group to DNA, DNA methyltransferases (Dnmt) express their effects. In this case, when a fetal brain expresses gonadal steroids, there is reduced Dnmt activity, which reduces methylation and causes masculinizing genes that would otherwise be repressed to be expressed.
Knowing that these two processes occur in the fetus lend to the question about gender identity. We know these processes are somewhat connected and dependent upon one another, since the “female” and “male” brain are characterized by which gender they primarily present in; however, I wonder if these processes being independent cause some of the gender identity issues we see in culture today? This would lead to a “female brain” being expressed in a male child or vice versa. Something somewhat comparable to this can be seen biologically when a female fetus is exposed to excess male hormones before birth or other complications occur, leading to hermaphroditism (1). Although the struggles surrounding these two scenarios are very different, they may both contribute to gender identity questions.
1. http://www.nlm.nih.gov/medlineplus/ency/article/001669.htm
Just like Hannah said, its amazing how a small change, at least what seems like a small change, can make a big difference. I think this is a great discovery with great potentials. However, I am interested to see different groups such as the LGBT may make of such discoveries like, "It appears that the methylation of masculinizing gene(s) results in feminine sexual behavior whereas male hormones block the methylation events so that these masculinizing genes are expressed." I know this doesn't explain why some are homosexual, but such information can be interpreted to fit different agendas.
ReplyDeleteThis is kind of old but very interesting.
ReplyDeletehttp://bayesianheresy.blogspot.com/2008/08/female-brain.html
Scientific investigations of gender and sexuality always turn up interesting findings. Among mammalian species, gender differences are some of the most pronounced characteristics and are noticeable from a very early age. Even as toddlers, humans can discern basic differences between male and female (even if they are not aware of all the biological specifics). Because of deeply ingrained concepts of gender roles and cultural views of male/female identity, these types of studies can carry strong undertones of personal opinions and assumptions. Thus, while the results themselves are untainted, the researchers’ evaluations are intrinsically flawed (or at the very least contain persistent bias), regardless of their conclusions. One could make this argument about almost any type of research, but it is especially pronounced in gender research. From one perspective, the female sex is the embryonic default since male hormone activation is needed to stimulate the development of androgenous features. The ovaries, for instance, must descend to produce testes in the male; without hormonal stimulation, they remain ovary precursors. Considering methylation, however, it might seem that male is the default setting.
ReplyDeleteMost likely, this issue will never be adequately resolved (from a “gender dominance” perspective) since human bias will always be a factor. However, it may be possible in the next century to determine which sex is the default setting and precisely how the process is modulated. There is still much about the human body we do not understand and time will undoubtedly increase our powers of elucidation.
I find this article to be very interesting. I agree with everyone above in the fact that this kind of discovery could mean interesting things fr our society. I specifically concur with the idea that it seems that the default brain would actually be masculine rather than feminine as methylation must occur in order for feminization.
ReplyDeleteApart from the many transgender issues that are surely to be reinforced by this research, I wonder what it means in the ever growing field of fertility. The issue of "designer babies" has been raging for quite some time now and if it is possible to force an infant to become male or female it will only be easier for parent to have the gender they want.
I also wonder if this research could be used in adults. If it can, I can only imagine that this will fuel the transgender debate. Those males who act more feminine may have "treatments" done to make them more masculine and vice versa. The debates would be heated and the ethics boards would be filled with controversy.
This is an interesting thing to consider as well as the potential ramifications for the results of this experiment as well as future studies to be done. Especially in regards to psychology and counseling. This in regards to those who are homosexual or transgender has huge ramifications. However, this would also extend to general individuals, assuming that the results were that everyone starts with a female brain. Also it is interesting as several individuals have mentioned above that intuitively it makes sense that the male brain is the default brain. Analysis of this adjacent to the theological claim that man was made first is a potentialgold mine of debate and controversy.
ReplyDeleteAll of the comments above were fun and interesting to read. So good points were made, and for the most part I'd say many similar things as already stated. So with that being said, here are a few things that are just a little different than the statements already made (so I'm not just repeating what others have already said).
ReplyDeleteAfter reading the first few questions at the top my thoughts were "of course the default brain is female, because the default gender is female." However, after reading the article my thoughts were changed and challenged (as usual). Might I say, this article was definitely in the top three for my favorites of all of the articles I have read on here, so thank you for the good, interesting, and new thought provoking read Dr. Daystorms.
I was excited when I was reading the article and knew some of the terms and processes that were talked about. It was a bit rewarding to be able to understand the processes (embryological development, DNA methylation & demethylation, transcription, etc.) and the "players" (DNA methyltransferases, masculinizing genes) that were being used to discuss this topic. This article definitely put to use information from ALL of the science classes that I have taken and that is both relieving and exciting. However, I am still a bit unfamiliar with some terms (CpG islands) but that encouraged me to do some research on them on my own, which is always fun.
This is an interesting article. I will have to do some more research to fully understand it, but I think that's worth it.
ReplyDeleteI find it very interesting that without the expression of methyltransferases the brain tends to act more masculine. I think this might insinuate that the default brain is in fact female. As far gender identity goes, this question brings about another question. Are people in fact born gay? In order to answer that question I believe it is important to research the extent of sexual behavior that is being expressed from both spectrums.
ReplyDeleteI think this article is especially interesting because it insinuates that the default brain in these mice is male. Their bodies have to consciously make the decision to methylate the male genes in order for the mice to have female tendencies. I must say that this completely contradicts everything I have learnt in my study of development prior to this moment. This new information raises so many questions in my mind though. The biggest one however, is if there could possibly be a genetic explanation for homosexuality. How would that affect the law, morality, and values in homophobic countries and among Christian communities? I personally intend to follow up on this research and learn as much as I can about this topic.
ReplyDelete