The central nervous systems as well as the brain->muscles and sensory cells->brain nervous pathways, need to be precisely wired for life to be possible. Moreover they are wired almost exactly the same way for the individuals of a same species (animal, man, insects, etc.).

This information, must therefore be somehow encoded in the DNA.

I have never heard of any study or theory on how this would be possible - only about how proteins are encoded, and I couldn't find any bit of information on this topic (I am not a biologist though).

I would like to have a broad idea of what is currently know about the construction of such networks, i.e. not detailed explanation but rather takeaways facts and references.

  • How is information about neural connections encoded in the DNA?

e.g. are there any genes linked with neurons (e.g. coding for neurotransmitters)? Do the DNA code for precise neural connections? Can development of specific parts of the brain be linked to specific parts of the DNA? How does a neuron knows from the DNA to which neurotransmitter be sensitive?

  • How are connections between specific neurons established?

e.g. how an axon does know where to establish deliver a potential? How can the end of an axon move to the correct place?

  • $\begingroup$ A small note on semantics: Science doesn't know anything. Humans know stuff; science is nothing but human knowledge. $\endgroup$ – WYSIWYG Nov 24 '15 at 8:47
  • $\begingroup$ Related post: biology.stackexchange.com/questions/31459/… $\endgroup$ – WYSIWYG Nov 24 '15 at 8:48
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    $\begingroup$ This question is broad. The genetic basis of instincts itself is a broad question and is something that is still not elucidated. I would, therefore suggest that you focus your question on a specific instinct or a neural pathway. You should also read about Hox genes and their effect on early embryonic patterning. It would be difficult to explain the level of complexity you are asking without you knowing about the early events in development. In short, as the question is written, one can write an entire book which would still not answer the question fully. $\endgroup$ – WYSIWYG Nov 24 '15 at 8:55
  • $\begingroup$ Hi WYSIWYG, I don't have the relevant background to ask specific questions about specific neural pathway as you suggested. However, I believe it is an interesting question and any piece of information is welcome. I am not looking for a book long answer neither precise description of all the mechanisms involved, but rather to have of a rough idea of what is going on and how much is known about this. $\endgroup$ – Nicolas Nov 24 '15 at 11:05
  • $\begingroup$ @Nicolas The edit is good, but I'm still unsure about what you want to know in a clear succinct answer. Re your bullet points 1.Networks are above a cellular level, the underlying genetics work at a protein level. To describe a genetic instruction for networks would take a monumental effort by an answerer. 2. This is more answerable, but still would take a lot of effort to answer and only for half the question. Consider rethinking this question and resubmitting it as a new question by itself. $\endgroup$ – James Nov 27 '15 at 3:23

Here's at least one paper describing some of what is known about development of neural network in Caenorhabditis elegans


It mentions at least one relevant gene

" There is evidence showing that several guidance molecules like Netrin and Nerfin-1 are expressed in the early stages of development. Netrin is a protein involved in axonal guidance in vertebrates as well as in invertebrates [21], [22], [23] and is specifically known to influence early path-finding events [23], [24], [25]. Nerfin-1 belonging to a highly conserved family of Zn-finger proteins, is found transiently expressed in neuron precursors and plays a role in early path finding. Studies involving pioneering neurons in the central nervous system of Drosophila melanogaster have shown that Nerfin-1, whose expression is spatially and temporally regulated [25], is essential in early axonal guidance. "

You can also have a lot at the Wikipedia article called "Development_of_the_nervous_system_in_humans"

One interesting fact is that C. elegans has 20 000 genes, 302 neurons and about 5000 chemical synapses, 2000 neuromuscular junctions and some 500 gap junctions. In humans there are an estimated 20 000-25 000 genes in humans, about 85 billion neurons and 100 trillion synapses.

This excerpt from http://www.tandfonline.com/doi/full/10.3109/0954898X.2011.638968 explains this seeming paradox though

"studies in a range of species suggest that fundamental similarities, in spatial and topological features as well as in developmental mechanisms for network formation, are retained across evolution. ‘Small-world’ topology and highly connected regions (hubs) are prevalent across the evolutionary scale, ensuring efficient processing and resilience to internal (e.g. lesions) and external (e.g. environment) changes. Furthermore, in most species, even the establishment of hubs, long-range connections linking distant components, and a modular organization, relies on similar mechanisms."

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  • $\begingroup$ Thanks for your answer. I understand that neuron migration is an important part of the process, that long distance connections are established early on, and that neural hubs also develop early on. Is it known if the the migration mechanisms using identical signal for each neurons or if they widely differ from neuron to neuron? I unfortunately can't access the second article which is not open access. Would you recommend any paper specifically about the encoding in the DNA? $\endgroup$ – Nicolas Nov 25 '15 at 12:52
  • $\begingroup$ I don't have a very detailed overview of all migrations mechanisms, but I think there's a handful basically. Here's one paper you might find interesting med.nyu.edu/dasenlab/assets/publications/Neuron_Review_2013.pdf $\endgroup$ – physicsnoob Nov 25 '15 at 13:30
  • $\begingroup$ Not sure if it's allowed to write here, but I usually use sci-hub.io if there's a paywall article I can't access. $\endgroup$ – physicsnoob Nov 25 '15 at 13:33

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