David Moore’s Developing Genome is almost comparable to popular non-fiction books that I have read in the past. Conveniently and witfully written as Jared Diamond’s Guns, Germs and Steel or Tim Flannery’s best-seller about the world’s fate in the future on the brink of a changing climate in The Weathermakers. There is a clever “ladder-like” introduction of biological terminologies as you go along reading without being overly technical and scientifically jargonised.
The book exhibits a perfect balance of introducing hard facts and concepts while citing related synonymous daily life scenarios. A literal example is how Moore tried to illustrate certain sections of the DNA strand into familiar household terms such as a “yarn spool.” I like how he put humorous connotations likening DNA processes like expression of a resulting trait or cellular product to “a party that came altogether spontaneously.” Overall, the writing style made reading the book enjoyable and interesting at least for the uninitiated with the subject topic.
Developmental biologists: epigenetics rings a bell
The word “epigenetics” was first introduced by Conrad Waddington in the 1940s to refer to the intrinsic interaction between genes and molecules at the cellular level, leading to phenotypic outcomes. However contemporary scientists would extend this definition as the interaction of the genetic (nuclear) material to extracellular environmental factors that are spatially situated “on top” of the genome (thus the epi word).
The book provided a good literature review, mostly over the last decade, on the advances of epigenetic research. Most of these highlighted the role of how genes (and consequently traits) are expressed or repressed in clinical psychology and bio-medical experiments. Curiously, the process is not gene-independent but is largely influenced by its interaction with the environment. Specific examples range from serious diseases/disorders (e.g. Prader-Willi, Angelman syndromes) to fur coloration pattern in cats. In addition, a number of important biological development processes such as female human X-chromosomes inactivation have been linked to epigenetic causes. So developmental biologists knew this concept right from the start!
Developmental stage is important because environmental effects influence the expression of genes mostly in early life. In practice, if the goal is to intervene or reverse these phenotypic expressions, the key is to look and act on these at different developmental stages. This is where epigenetics comes in to elucidate the adverse effects of early life exposure to external factors such as bad (or good) experience, memory and diet deprivation during developmental stages.
It is indeed Nature + Nurture
Turning the book’s page one at a time has been revelational. All along, I have been versed with a misconstrued (mostly during my biology undergrad days) idea that sole genetic makeup always determines what traits, physiological or even behavioural tendencies one have in later life. Apparently, this is one of the main arguments raised by Moore about the need to dismiss popular metaphorical fallacies associated with how we use and interpret the words DNA and genes. For example, genes were popularly viewed as a “blueprint system”, a “program” (computer) and even likening it to a film script.
These in a way are misleading metaphors, because they convey a “grandmaster” plan or seem to entail a pre-deterministic fate of how genes should function and develop. Epigenetic systems are much more of a two-way process where genes’ activities are largely influenced by external factors and vice-versa. To quote, “it is not what (genes) you have, but more importantly how those genes perform and work.”
The book enumerated a wealth of supporting evidence from recent and emerging research on behavioural epigenetics that link the effect of environmental factors to genetic makeup at the individual level (i.e. DNA methylation, histone modifications). There were early experiments such as investigating consequences of epigenetic states of good or bad experience (from parental care) to eventual offspring behaviour. However, it is not clear how epigenetic factors affect individuals in succeeding generations on the population level in natural environments or the mechanisms behind it.
A retrospect: Darwin’s finches
The idea that our genome continuously communicates with the environment “epigenetically” puzzles me at this stage. But one thing I realise is that isn’t this supposed to be how organisms ultimately adapt and evolve under Darwinian synthesis of evolution? This reminds me of the outcomes of some classic empirical work in ecology and evolution, such as the long-term study of Darwin’s finches by the British couple Peter and Rosemary Grant in the Galapagos Islands.
Decades of field data allowed them to observe changes in feeding adaptations exhibited as adjustments in morphology and habitat use due to an ever-changing environment. What happened really was successful adaptation and transgenerational inheritance of novel phenotypic changes, which maybe are partly mediated epigenetically.
Re-inventing Darwinian and Lamarckian views of evolution
One of the main arguments of the book is the need to revisit the universally accepted theory of evolution or Neo-Darwinism, which is based on changing gene frequencies across a particular genome in space and time. Following the recent advances in mechanistic study of epigenetics, there is a need to explore how such processes play a role in broad evolutionary biology questions, like speciation and natural selection. To quote:
“There is a need to understand the relation between heredity and on the premise that natural selection has different results across a spectrum of heritable variations. With epigenetic systems in place and recognised, a research that will integrate development and evolution would result to a more powerful Darwinian theory.”
Amazingly, this realisation brings back again (after all) Charles Darwin and his “Origin of Species”, which is compatible and complementary to the Lamarckian view. The unlikely return to Lamarckian views of evolutionary mechanisms of inheritance, which states that it should encompass “both genetic and non-genetic developmental resources”, is unanimously sensible at this point.
In the end, Moore believes that the burgeoning field of epigenetics has finally provided the mechanistic explanation to Darwin’s theory. As epigenetics becomes more prevalent and influential in so many fields, such as in medicine, pathology and law (I am hoping so!), it is predicted that it will be a “monumental” step towards how we view life. Its impact is potentially revolutionary in the sense that it transcends from the minute DNA molecules to social and cultural hierarchies of human civilisation.