This 2017 UK/Spanish review subject was biological variability:
“No two cells in a cellular population are the same, and no two individuals of a multi-cellular species are identical—not even if they share the same genetic makeup like monozygotic twins or cloned animals.
Epigenetic and gene expression variability are key contributors to phenotypic differences..There are many possible sources of epigenetic and transcriptional variability, which can be divided into three main categories:
- individual-intrinsic factors;
- environmental factors; and
- random fluctuations, also referred to as stochasticity.”
Most of the review cited cell studies. The reviewers cited their own studies in the Introduction section, for example:
“These studies were among the first to classify disease status or aggressiveness based on variability, where the classical comparison of mean DNA methylation or gene expression levels was not informative.”
to help support a later observation:
“It is critical to obtain a measurement of variability that is independent of the mean to ensure to not confound changes in variability with shifts in mean.”
The review didn’t cover a pertinent aspect of the subject: how standard research approaches miss detecting biological variability.
For example, from Changing an individual’s future behavior even before they’re born that referred to the methodology of genome-wide association studies (GWAS):
“When phenotypic variation results from alleles that modify phenotypic variance rather than the mean, this link between genotype and phenotype will not be detected.”
Another omission was the point made in A study of DNA methylation and age:
“Due to the methods applied in the present study, not all the effects of DNA methylation on gene expression could be detected; this limitation is also true for previously reported results.
The textbook case of DNA methylation regulating gene expression (the methylation of a promoter and silencing of a gene) remains undetected in many cases because in an array analysis, an unexpressed gene shows no signal that can be distinguished from background and is therefore typically omitted from the analysis.”
The reviewers also didn’t cover variability in phenotypic behaviors. I’ll repeat my thoughts from A limited study of parental transmission of anxiety/stress-reactive traits:
“How did parental behavioral transmission of behavioral traits and epigenetic changes become a subject not worth investigating? These traits and effects can be seen everyday in real-life human interactions, and in every human’s physiology.”
Perhaps these omissions reflected the reviewers’ focus on their specialties?
Perhaps it isn’t politically correct to discuss or fund research on aspects of biological variability that would advance science by falsifying preferred previous findings? Or advance science by measuring the extent of parental involvement in shaping their offspring’s behavioral and biological variability?
What do you think?
http://onlinelibrary.wiley.com/doi/10.1002/bies.201700148/full “Epigenetic and Transcriptional Variability Shape Phenotypic Plasticity”