Can Intelligence be Genetically Engeneered?
"SMART GENES? Reads the title of a 1999 article
in Time magazine (2). Could it be true? Could scientists have finally cracked
the Holy Grail of genetics: genes that determine intelligence? The subtitle
continues: "A new study sheds light on HOW MEMORY WORKS and raises questions
about whether we should use genetics to make people brainier" (2). This
headline is accompanied by a "brainy" looking child and all sorts
of thought provoking images (E=MC2, textbooks, violins and test tubes). It first
glance the reader is struck with the awe-inspiring possibility that humans could
actually engineer smarter children.
So is it true? The article follows with talk of a strain of mice created by scientists at Princeton, M.I.T. and Washington University that supposedly has enhanced memory and learning skills. The article stated that this strain of mice, aptly named "Doogie" after televisions kid genius Doogie Howser, has been engineered to have more of the receptor protein NMDA in its brain, allowing it to learn faster that its wild-type counterparts (2). So is that it? Have all of humanity's problems been solved? As the paper continues, it soon becomes apparent that this is not actually the case. But before we go that far, let's hear what the scientists themselves have to say.
The article that captured the front page of the September 13, 1999 issue of time was based on a publication by Ya-Ping Tang and others in the September 2, 1999 issue of Nature, entitled "Genetic enhancement of learning and memory in mice" (3). This article, although written in a much more thorough and scientific style, seems to support the conclusions suggested by the Time article. Tang et al. were able to create a strain of mice with enriched expression of the NR2B subunit of N-methyl-D-aspartate (NMDA) was in their cortex and hippocampus. NMDA is an ion channel that requires a double signal to open and has long been suspected to play an important role in memory formation and learning (3). It is expressed at high levels in the brain of young mammals but not in adults. Tang et al. postulated that elevating levels of NR2B in adults might give them the learning abilities of youngsters. Having created "Doogie" and verified high expression of NR2B, Tang et al. used a variety of memory tests and found that these engineered mice learned significantly more quickly than wild type mice. The article ends with the promising phrase "This study also reveals a promising strategy for the creation of other genetically modified mammals with enhanced intelligence and memory"(3).
So that's it, right? Science has triumphed and a new generation of young Einsteins is right around the corner. Not so fast, back to the Time article. As the time article continues, it quickly becomes apparent that the reality is much more complicated than this study suggests.
1. Mice and Humans are very different creatures. Although we share many similarities, The human brain is obviously much more complex than that of a mouse and what works in mice probably wont work exactly the same for humans (1).
2. These mice displayed enhanced memory-making skills when put through a series of simple tests. Does this mean that they are more intelligent? The link between memory and intelligence is hardly clear or simple. New memories may interfere with old memories and there is no evidence that the total memory capacity of these mice is any greater than wild type mice. Also, enhanced memory may have other side effects, for example, these mice were slower to forget their fears (1).
3. Memory itself is not as simple as it might seem. There are several types of memory that work together and with other parts of our brain. This one molecule invariably only a small part of this big system and thus only regulates a small part the whole system (2).
4. What are the side effects of this overexpression? The mice seem healthy but other studies have ties NMDA to seizures, stroke, and drug addiction. How would this effect humans?
So, in short, this was a big discovery, but it must be taken with a grain of salt. Tang et al. have made a big step in understanding part of memory formation in mice. The problem is that every discovery raises more questions than it answers. The human mind is so complex that we will probably never understand it fully. In this case, the popular article in Time, although it opened with a slightly misleading title, brought up many of the criticisms that might not normally be considered and did a good job of putting this discovery in context.
1. No Author Listed. 1999. "A Mouse's Tale that Grew in the Telling". Nature Neuroscience. 11: 925.
1. Michael D. Lemonick. Smart Genes? Time. September 13, 1999: 54-58.
2. Tang, YP et al. 1999. "Genetic enhancement of learning and memory in mice." Nature. 401: 63-69.
OMIM entry on the 2B Subunit of NMDA
mRNA sequence of the Human 2B subunit of NMDA
Amino Acid sequence of the Human 2B subunit of NMDA
Another Good Site on NMDA
NMDA (the National Minature Donkey Association)
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