Speciation, Phenotypic Variation and Plasticity: What Can Endocrine Disruptors Tell Us?

Abstract

Phenotype variability, phenotypic plasticity, and the inheritance of phenotypic traits constitute the fundamental ground of processes such as individuation, individual and species adaptation and ultimately speciation. Even though traditional evolutionary thinking relies on genetic mutations as the main source of intra- and interspecies phenotypic variability, recent studies suggest that the epigenetic modulation of gene transcription and translation, epigenetic memory, and epigenetic inheritance are by far the most frequent reliable sources of transgenerational variability among viable individuals within and across organismal species. Therefore, individuation and speciation should be considered as nonmutational epigenetic phenomena.

Phthalate Exposure and Long-Term Epigenomic Consequences: A Review

“…The epigenetic tags of the chromatin are of two types-(i) transient which can be removed and (ii) permanent which is heritable (Ayala-Garcia et al, 2013). The transient epigenetic tags enable the organism to adjust their gene expression status in relation to changes in their environment-in contrast permanent epigenetic tags gives rise to an epigenetic memory which modulates the cells' genetic and metabolic response to environmental changes for the rest of the organism's life (Ayala-Garcia et al, 2013). When permanent chromatin epigenetic tags occur in the stem cells, gametes-they are inherited by their progenies both at the cellular and organismal levels and are thus transgenerationally heritable (Dolinoy et al, 2007;McCarrey, 2012).…”

“…Thus, the highly dynamic process of epigenetic tagging as perpetuated by the epigenetic memory is responsible for the phenotypic plasticity in an organism. Tagging occurs as a response to changes in environmental conditions at any time point in the life course (Ayala-Garcia et al, 2013). Humans are simultaneously exposed to several xenobiotics and thus the interaction of phthalates with other environmental toxins should be taken into account when studying their roles in causing diseases in the population (Benjamin et al, 2017).…”

“…Epigenetic Changes in Sperm Current research findings suggest that several adulthood diseases are programmed in utero as a result of maternal exposures to endocrine disruptors like DEHP. Those diseases are linked with critical genes which are epigenetically modified by DNA methylation or modification of histone tails (Martinez-Arguelles et al, 2009;Wu et al, 2010;Anderson et al, 2012;Strakovsky and Pan, 2012;Ayala-Garcia et al, 2013). The first reprogramming event occurs in the genome of the germ cell precursors while they colonize the embryo's urogenital crest.…”

“…The next event of epigenetic reprogramming of both the paternal and maternal chromosomes occurs shortly after fertilization. Thus, experiments which involve prenatal and postnatal exposure to phthalates may unravel mechanism underlying the epigenetic modulation of gene expression for phenotypic variability between individuals and across species (Ayala-Garcia et al, 2013).…”

Male Ejaculatory Endophenotypes: Revealing Internal Inconsistencies of the Concept in Heterosexual Copulating Rats

“…The endophenotype’s notion is at the core of this trend ( Gottesman and Gould, 2003 ; Burmeister et al, 2008 ; Garcia et al, 2010 ; Iacono et al, 2014 ; Zietsch et al, 2015 ). Sizeable phenotypic variations, nonetheless, may also emerge through epigenetic mechanisms ( Ayala-García et al, 2013 ; see also comments on the effects of epigenetics on endophenotype expression in Hasler et al, 2006 ). That this might be the case for the copulator male rats included in our sample is supported by data showing that relative gene expression levels of DNMT-1 and DNMT-3a differ greatly across individuals; these enzymes are involved in the transferring of methyl groups to DNA and thus in the epigenetic regulation of gene expression.…”