The Role of Cells in Encoding and Storing Information: A Narrative Review of Cellular Memory

" Multiple studies have demonstrated that memories can be encoded and stored in cells. Evidence suggests that these memories can then be transferred between individuals through organ transplantation. Additionally, observations in organisms that lack a nervous system, such as bacteria, fungi, and plants, expand traditional memory concepts. This review highlights and compiles novel research from the last few decades that explores information encoding and storage at a cellular level across a wide variety of disciplines." {Credits 1}

DNA memory:

" About 1% of our DNA codes for proteins, while the other 99% is noncoding DNA, i.e., it does not code for proteins. Noncoding DNA contains sequences that determine when and where genes are turned on and off. These regulatory elements are sites where transcription factors attach to DNA and turn on or off the processes by which genetic information is converted into proteins. Certain regions of noncoding DNA are involved in RNA processing and regulate the conversion of messenger RNA (mRNA) into proteins. These include transfer RNAs (tRNAs), ribosomal RNAs (rRNAs), small nuclear RNAs (snRNAs), small nucleolar RNAs (snoRNAs), and others [62]." {Credits 1}

" A third method for encoding and storing information utilizing DNA is epigenetic memory. Rather than encoding information in a series of nucleotides on a strand of DNA, information is encoded in the way DNA is packaged and modified [63]. Epigenetic changes occur when enzymes attach or remove molecules to or from chromatin, or when RNAs are produced, resulting in a modification of gene expression. Examples of epigenetic changes include DNA methylation, histone modification, and the production of microRNAs (miRNAs). This entire process can either enhance or suppress the production of gene products [46]. Persisting epigenetic changes create an epigenetic code that determines whether a specific gene is transcribed [64]. Epigenetic changes also encode information that can be stored and retrieved over time. The entirety of an individual’s epigenetic changes at any given point in time is known as the “epigenome” [65]." {Credits 1}

" Epigenetic memory can also be passed down from one generation to the next. This is known as “transgenerational epigenetic inheritance” or “epigenetic inheritance” [67,68]. Epigenetic inheritance allows for a person’s health or development to be influenced by the lived experiences of not only their parents but also their grandparents and previous generations, transferred through epigenetic memory embedded in genetic material. A recent study showed that the transmission of epigenetic memory can occur across multiple generations. By manipulating a histone modification (H3K27me3) in sperm chromosomes, which is typically involved in gene repression, researchers observed altered gene expression in offspring, suggesting a direct transmission of epigenetic memory [69]. Another study investigated pregnant women who were present in New York City during the World Trade Center attacks on September 11, 2000. Researchers found that their offspring carried epigenetic signs of PTSD, an indication of the trauma their mothers had experienced. Mothers who had PTSD gave birth to babies with lower cortisol levels, an epigenetic change that occurred in the womb [70-72]." {Credits 1}

" A fourth mechanism by which information can be stored in DNA is via EM [electromagnetic] memory. During transcription, when DNA is converted to RNA, the two polynucleotide strands of DNA are separated, and the hydrogen bonds are broken. As a result of the breaking of these hydrogen bonds, a modulation occurs in the magnetic field in the form of an EM signal. This EM signal can send information from the cell nucleus to other cells. At the receiving cells, this process is reversed, and the transported information is converted from a magnetic wave back into a chemical structure [73]. Researchers have suggested that the ability to emit EM waves may be a property of all double-stranded helical DNAs [74,75]. Montagnier et al. found that treatment of DNA with DNase, which degrades DNA, destroys the DNA’s ability to emit EM signals. This demonstrates that it is the DNA and not some other subcellular component that emits the EM signals [75]." {Credits 1}

Protein memory:

" Just as the packaging of DNA into chromosomes results in epigenetic memory, the folding of proteins can also influence memory. One type of protein that influences memory is a prion. Prions are proteins that can shift between and exist stably in multiple functionally distinct conformations, and at least one of these conformations is self-replicating [54]." {Credits 1}

" Prions were discovered in the 1980s by Stanley Pruisner, who found that they cause transmissible, fatal neurodegenerative diseases such as Creutzfeldt-Jakob disease, bovine spongiform encephalopathy (Mad Cow disease), and kuru [81,82]. In addition to causing disease, prions are also a channel for the replication of heritable information, similar to DNA or RNA, and assist with the formation of long-term memory in humans [54,83-85]. The replication of prions provides a durable form of molecular memory [54]." {Credits 1}

" In plants, prion-like proteins have been found that encode stress memory, which occurs via priming. Priming occurs when a previous brief exposure to stress primes the plant for future episodes of stress by facilitating a more rapid and heightened response of resistance." {Credits 1}

Evidence for cellular memory (organ transplant recipients):

" Neuropsychologist Paul Pearsall explored personality changes in heart transplant recipients and found that these individuals can take on the personality characteristics of their donor, despite having no information about their donor prior to their transplant [47]. Subsequent research found that changes in the personalities of heart transplant recipients mimicked the personality traits of their donors. These changes included preferences for food, music, art, sex, recreation, and career, as well as transplant recipients recalling the names and sensory experiences of their donors. This suggests that memories can be transferred from donor to recipient via the transplanted heart [48]." {Credits 1}

" Despite numerous challenges, research has begun to investigate the prevalence of personality changes in organ recipients. A cross-sectional study found that up to 89% of all transplant patients experienced self-reported personality changes following organ transplantation, regardless of which organ was received. These changes were equally likely to occur whether the transplanted organ was a heart or a different organ [94]. Additionally, it is important to note that these personality changes include a wide range of experiences, from newfound preferences for food and music to changes in temperament and behavior. This wide range of changes makes it difficult to pinpoint the exact role of cellular memory and the types of information that may be encoded and transferred with the transplanted organ. Various studies across the globe have found that organ recipients struggle to integrate their sense of “self” and “other” following transplantation. Many also attribute newly acquired characteristics or traits to the organ they received. However, deeper investigations into these accounts rarely occur [95,96]." {Credits 1}

Cellular memory and the heart:

" Another question that remains to be answered is: how can memories be transferred from a donor’s heart to a recipient? Cardiac cells contain all of the cellular components that have previously been identified with memory. These include DNA, RNA, prions, microtubules, EM waves, and cell membranes. If memories are stored in these cellular components, it might be possible for the recipient of a new heart to retrieve these memories from the donor’s heart. Furthermore, research suggests tiny vesicles known as exosomes present a potential mechanism for transferring memories stored in the heart to cells in other organs of the body [97]. Exosomes play a vital role in intercellular communication by transferring proteins and various types of nucleic acids, such as DNA and RNA, from one cell to another [98-100]." {Credits 1}

" Exosomes could transport information from other organs to the brain as well. Researchers at the University of Geneva found that blood transfusion recipients described changes in their mood, behavior, and memories after receiving blood from another person [103]. These findings suggest that blood transfusions may result in personality changes, and a potential mechanism explaining these changes is the transfer of information via exosomes from donor organs to recipients." {Credits 1}

" In addition, the heart possesses its own intrinsic nervous system known as the “intracardiac nervous system” [104] or the “heart-brain” [105]. This system includes an intricate network of neurons, neurotransmitters, proteins, and immune cells, all of which are capable of encoding, storing, and retrieving information. Studies have shown that the neural network of the heart is involved in decision-making and storing both short-term and long-term memories, with approximately 40,000 sensory neurites potentially playing a critical role in memory transfer [106]. These specialized nerves form connections with the recipient's body following the transplantation of the organ." {Credits 1}

Further evidence for cellular memory/non-neuronal memory:

" Slime molds, a group of unrelated eukaryotic organisms without brains, exhibit behaviors that require memory, such as moving toward food and solving mazes [109]. One example is the slime mold Physarum polycephalum, which is a large amoeba-like cell that changes shape as it moves. This single-celled organism is also capable of solving a labyrinthian maze by first exploring all possible paths, then changing its shape to form a single thick tube covering the shortest distance between the two food sources. This suggests that the slime mold can remember which paths provide the shortest distance to the desired goal [9]." {Credits 1}

" Fungi have demonstrated the capacity to remember, even though they have no brain, central nervous system, or neural network. In one study, researchers primed a group of grassland fungi with high temperatures and then exposed them to a severe heat shock. In comparison to a control group, the primed fungi grew more when exposed to the second shock, suggesting that the compensatory mechanisms from the earlier high temperatures were remembered and deployed quickly at the second shock. These primed fungi also remembered the first stressful shock for up to 12 hours after the event, indicating prolonged memory storage despite a lack of a neural network [110]. According to mycologist Nicholas P. Money, mycelia exhibit spatial recognition, decision-making, learning, and short-term memory, and may even possess the capability of consciousness [111]." {Credits 1}

" A fascinating insight into the storage of memory outside the brain has been demonstrated in planarian flatworms, a non-parasitic flatworm that can regenerate any part of its body through its abundance of adult pluripotent cells. Despite their small size, planarian flatworms have a centralized nervous system, a brain, and can regrow a new head after it is severed from its tail. Researchers trained planarian flatworms using classical conditioning and then cut the planarian flatworms in half. The flatworms that regenerated from the tail half formed an entirely new head and brain. These previously headless flatworms were found to retain memory of their conditioned learning [112,113]. This strongly suggests that the physical body stored memory that was transferred to the new brain after regeneration, supporting the existence of cellular memory." {Credits 1}

{Credits 1} 🎪 Flores A I, Liester M B (November 05, 2024) The Role of Cells in Encoding and Storing Information: A Narrative Review of Cellular Memory. Cureus 16(11): e73063. doi:10.7759/cureus.73063. © 2024 The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License.