All of “like kind” (Part 2)

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Mon, 19 Jan 2015 11:51:50 -0500

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The 2015 Society for Integrative and Comparative Biology (SICB) presenters may not recognize how much progress has been made since the 2013 ecological epigenetics symposium. For example, since then authors claimed “…ctenophore neural systems, and possibly muscle specification, evolved independently from those in other animals.” https://dx.doi.org/10.1038/nature13400

Six months later, other authors traced signaling factors found in vertebrates to the origin of nerve cell centralization via the diffuse nerve net of animals like the sea anemone. https://dx.doi.org/10.1038/ncomms6536 That fact suggests ecological variation is linked to ecological adaptations in morphological and behavioral phenotypes via signaling protein concentrations that differentiate various cell types in body axes and the central nervous system.Links across species from the epigenetic landscape to the physical landscape of DNA in organized genomes appear to have their origins in the conserved molecular mechanisms of  RNA-directed DNA methylation and RNA-mediated protein folding.

Two weeks after the publication that refuted ideas about independently evolved neural systems or muscle specification — and perhaps refuted the independent evolution of anything else, SICB presenters linked crustaceans to insects. Apparently, they’ve learned that the same set of microRNAs controls expression of the genes for rate-limiting enzymes that control the hormone production of different hormones in insects and crustaceans.

Why were they left with any questions about how crustaceans and insects could all be part of one big family? They linked RNA-mediated cell type differentiation to what we described in our section on molecular epigenetics in our 1996 Hormones and Behavior review. From Fertilization to Adult Sexual Behavior https://www.hawaii.edu/PCSS/biblio/articles/1961to1999/1996-from-fertilization.html

If the first part on my comment is published to the Science Magazine site, I will let others know in this blog post….

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The first part of my comment was published on 1/29/15, which was 10 days after its submission. I will submit the continuation (below).

Elekonich and Robinson (2000) “Organizational and activational effects of hormones on insect behavior” https://www.ncbi.nlm.nih.gov/pubmed/10980296 extended our model to insects from differences that arise from different epigenetic modifications of an otherwise identical MAT locus of yeasts. Elekonich and Roberts (2005) “Honey bees as a model for understanding mechanisms of life history transitions” https://www.ncbi.nlm.nih.gov/pubmed/15925525 extended the findings from yeasts to insects and from insects to nutrient-dependent pheromone-controlled cell type differentiation in the honeybee model organism.

Given what is currently known about the 3D genome, it seems clear that nutrient-dependent and pheromone-controlled nucleome structure changes as cells age, differentiate, and divide in all species. See: Inching toward the 3D genome https://www.sciencemag.org/content/347/6217/10.short

One way to understand the 4D genome is to view it in the context of what is already known about the biophysically constrained chemistry of protein folding and conserved molecular mechanisms that link cell type differentiation to biodiversity in species from microbes to man via epigenetically effected changes in the microRNA/messenger RNA balance in all animals. Alternatively, some people may still believe that neural systems and behavioral phenotypes evolved independently in some animals. If not, all questions about which animals belong in what families can perhaps best be addressed in the context of the 4D genome and biodiversity manifested in nutrient-dependent RNA-mediated pheromone-controlled morphological and behavioral phenotypes.