This EMBO Journal review series focuses on molecular memory. When talking about memory, two biological processes come easily to mind – memory formation in the brain and memory formation in the adaptive immune system.
While these topics are of great interest, we would like to highlight other aspects of molecular memory in this focus series. We want to share our excitement for fields in the biomedical life sciences that have only recently gotten more attention, and that all allow the formation of memory from a conventional or non-conventional point of view: from epigenetic memory in plants to memory in the innate immune system. Our series also includes reviews on epigenetic processes and small RNAs in memory function and behavioral changes, thus presenting new molecular insight into what is happening in the brain during memory formation. We hope that our reviews will provide new ways of thinking about molecular memory. Enjoy!
|Epigenetic memory in plants
Mayumi Iwasaki & Jerzy Paszkowski
Epigenetics refers to heritable changes in patterns of gene expression that occur without alterations in DNA sequence. The epigenetic mechanisms involve covalent modifications of DNA and histones, which affect transcriptional activity of chromatin. Since chromatin states can be propagated through mitotic and meiotic divisions, epigenetic mechanisms are thought to provide heritable ‘cellular memory’. Here, we review selected examples of epigenetic memory in plants and briefly discuss underlying mechanisms.
|Mechanisms of epigenetic memory and addiction
Luis M Tuesta & Yi Zhang
Epigenetic regulation of cellular identity and function is at least partly achieved through changes in covalent modifications on DNA and histones. Much progress has been made in recent years to understand how these covalent modifications affect cell identity and function. Despite the advances, whether and how epigenetic factors contribute to memory formation is still poorly understood. In this review, we discuss recent progress in elucidating epigenetic mechanisms of learning and memory, primarily at the DNA level, and look ahead to discuss their potential implications in reward memory and development of drug addiction.
|Epigenetic memory: the Lamarckian brain
Recent data support the view that epigenetic processes play a role in memory consolidation and help to transmit acquired memories even across generations in a Lamarckian manner. Drugs that target the epigenetic machinery were found to enhance memory function in rodents and ameliorate disease phenotypes in models for brain diseases such as Alzheimer's disease, Chorea Huntington, Depression or Schizophrenia. In this review, I will give an overview on the current knowledge of epigenetic processes in memory function and brain disease with a focus on Morbus Alzheimer as the most common neurodegenerative disease. I will address the question whether an epigenetic therapy could indeed be a suitable therapeutic avenue to treat brain diseases and discuss the necessary steps that should help to take neuroepigenetic research to the next level.
Immune memory has traditionally been the domain of the adaptive immune system, present only in antigen‐specific T and B cells. The purpose of this review is to summarize the evidence for immunological memory in lower organisms (which are not thought to possess adaptive immunity) and within specific cell subsets of the innate immune system. A special focus will be given to recent findings in both mouse and humans for specificity and memory in natural killer (NK) cells, which have resided under the umbrella of innate immunity for decades. The surprising longevity and enhanced responses of previously primed NK cells will be discussed in the context of several immunization settings.