The transition from an egg to a developing embryo is one of life’s most remarkable transformations. Yet little is known about it. Now Whitehead Institute researchers have deciphered how one aspect – control of the all-important translation of messenger RNAs (mRNAs) into proteins – switches as the egg becomes an embryo. That shift is controlled by a beautiful mechanism, which is triggered at a precise moment in development and automatically shuts itself off after a narrow window of 20 to 90 minutes.
As an egg develops, it stockpiles mRNAs from the mother because it will not have time to create new mRNAs during the rapid development of a very early embryo. When fertilized the egg becomes an embryo, the stashed maternal mRNAs are pressed into service for a brief window before the embryo starts transcribing its own mRNAs. This change occurs very early; in humans, only two to four cell divisions occur before this transition is executed. Whitehead Member Terry Orr-Weaver studies the control of translation of maternal mRNAs in the model organism Drosophila, or the fruit fly, because its developmental strategy offers experimental advantages.
In the research, Orr-Weaver and her lab determined that key to the transition are the three molecules that form the enzyme PNG kinase: PNG, PLU, and GNU. Orr-Weaver describes PNG and PLU as “tight buddies” that are always locked together, including in the mature egg. At that point in development, GNU has phosphate molecules tacked to it, which impede its binding to PNG-PLU.
When an egg is activated, levels of another enzyme that adds phosphates to GNU in the egg precipitously drop, allowing GNU to lose its phosphates and bind to PNG-PLU. Once together, the trio comprises the PNG kinase that triggers the translational control of the maternal mRNAs. Because PNG kinase also triggers the breakdown of GNU, the kinase self-destructs, which quickly and irreversibly squelches the translation of maternal mRNAs. This elegant feedback loop and the switch it controls are described in an article in eLife. (1)
An elegant mechanism of life. Does it really matter if this is something random or something deliberately designed? Does our need to name and categorize things (as random, non-random etc) make it necessary that any categories at all exist in the cosmos?
Imagine that you observe the above-mentioned mechanism. And you just sit in awe in front of the grandeur of nature and what we call life, paying attention to every little detail of how this life came to be.
Does it matter if there is a God?
Does it matter if there is death?
Does it matter what life is?
All great questions in philosophy have been generated by people who were too much preoccupied with thinking that they sat in front of the miracles of the cosmos. People who did not want to just sit in awe but who wanted to make things “comprehensible”. But life is not something to understand. Life is something to experience. And you can never truly experience something is you are so distanced from it in order to understand it.
Phosphates to GNU dropping…
mRNA translation started…
A being is created…
Let it breath.
Let it cry.