Epigenetics is the study of the encoding, decoding, and inheritance of biological information above and beyond the DNA sequence of the genome. Traditionally, these phenomena have been studied in the context of “cellular memory”; that is, the ability of each specialized cell in a multicellular organism to maintain identity and function over time and cell divisions. Despite having exactly the same genetic information, our liver cells divide into more liver cells and our blood cells divide into more blood cells.
It is widely believed that a considerable portion of epigenetic information is written as small chemical modifications on chromatin, the assembly of DNA, RNA, and protein that packages chromosomes inside the cell nucleus. Chromatin modifications punctuate the otherwise monotonous sequence of DNA letters into sentences, paragraphs, and chapters, so that cells can find and use the right sequences at the right time. The exact molecular details of these processes are largely unknown and under intense investigation, in part because they are often disrupted in cancer.
Epigenetic regulation of gene expression is critical for proper brain development and, possibly, function. Mutations in epigenetic factors often accompany neurological and neurodevelopmental disorders. Changes in brain state, such as those caused by fear conditioning, attachment, addiction, and learning, leave marks on chromatin structure. It has, however, been difficult to link epigenetic pathways to brain function in a direct mechanistic manner, arguably due to the lack of model systems simple enough to be deconstructed and complex enough to utilize the entire spectrum of epigenetic regulation. To better understand the role of epigenetic pathways in brain function and behavior, the Bonasio lab is developing a new potential model system, ants. In ants, workers and queens display dramatically different behavioral repertoires despite carrying the same genetic information. We hypothesize that these caste-specific behaviors are ultimately controlled by molecular differences in the ants’ brains and likely encoded by epigenetic pathways. Because the differences are so pronounced and yet highly reproducible across castes, studies in ants will help uncover molecular links between epigenetics and behavior, which might otherwise be obfuscated by natural biological and behavioral variability in more complex organisms.
Given the high level of conservation of epigenetic pathways in multicellular organisms, we believe that studying how they regulate ant behavior will help us understand their potential contribution to the function of much more complex animal brains, including our own.