Life is Emerging: Review of Siddhartha Mukherjee’s Song of the Cell
The DNA double helix is often the image spiraling at the center of 21st century advances in biomedicine and the growing bioeconomy. And yet, DNA is molecularly inert. DNA, the code for genes, is not alive and is not strictly necessary for life. Ought life be at the center of our communication of living systems? Is not the Cell a superior symbol of life and our manipulation of living systems?
A code for life isn’t a code without the life that instantiates it. A code for life must be translated. The cell is the basic unit of that translation. The cell is the minimal viable package of life as we know it. Therefore, cell biology is at the center of biomedicine’s greatest transformations, suggests Pulitzer-winning physician-scientist Siddhartha Mukherjee in his latest book, The Song of the Cell: The Exploration of Medicine and the New Human.
The Song of the Cell begins with the discovery of cells and of germ theory, featuring characters such as Louis Pasteur and Robert Koch, who brought the cell “into intimate contact with pathology and medicine.” This intercourse would transform biomedicine, leading to the insight that we can treat disease by thinking at the cellular level. The slightest rearrangement of sick cells might be the path toward alleviating suffering for the organism: eroding the cell walls of a bacterium while sparing our human cells; inventing a medium that coaxes sperm and egg to dance into cellular union for in vitro fertilization (IVF); designing molecular missiles that home to the receptors decorating the exterior of cancer cells; teaching adult skin cells to remember their embryonic state for regenerative medicines.
Mukherjee uses the bulk of the book to elucidate key cell types in the human body, along with their “connective relationships” that enable key organs and organ systems to function. This includes the immune system, the heart, the brain, and so on. Mukherjee’s distinctive style features compelling anecdotes and human stories that animate the scientific (and unscientific) processes that have led to our current state of understanding. In his chapter on neurons and the brain, for example, he integrates Santiago Ramon y Cajal’s meticulous black ink sketches of neurons into Mukherjee’s own personal encounter with clinical depression. In one lucid section, he interviews Dr. Helen Mayberg, a pioneering neurologist who takes seriously the descriptive power of her patients’ metaphors, as they suffer from “caves,” “holes,” “voids,” and “force fields” that render their lives gray. Dr. Mayberg aims to stimulate patients’ neuronal cells in a manner that brings back the color.
Beyond exposing the insight and inventiveness that has arisen out of cell-based thinking, it seems that Mukherjee’s bigger project is an epistemological one. The early chapters of The Song of the Cell continually hint at the potential for redefining the basic unit of biology as the cell rather than the gene. The choice to center biomedicine around cells is, above all, a conspicuous choice not to center it around genes (the subject of Mukherjee’s previous book, The Gene), because genes dominate popular science communication.
This choice of cells over genes is most welcome. Cells are alive. Genes are not. Letters—such as the As, Cs, Gs, and Ts that represent the nucleotides of DNA, which make up our genes—must be synthesized into a word or poem or song that offers a glimpse into deeper truths. A key idea embedded in this thinking is that of emergence. Whether in ancient myth or modern art, creation tends to be an emergent process, not a linearly coded script. The cell is our current best guess for the basic unit of life’s emergence, turning a finite set of chemical building blocks—nucleic acids, proteins, sugars, fats—into a replicative, evolving system for fighting stasis and entropy. The cell’s song is one for our times, for it is the song of biology’s emergence out of chemistry and physics, into the “frenetically active process” of homeostasis.
Re-centering our view of biology has practical consequences, too, for how we think about diagnosing and treating disease, and for inventing new medicines. Centering cells presents a challenge: which type of cell to place at the center? Rather than default to the apparent simplicity of DNA as a symbol because it represents the one master code for life, the tension in defining the diversity of cells—a mapping process still far from complete in cutting-edge biology laboratories—can help to create a more thoughtful library of cellular metaphors to shape both the practice and communication of biology.
Further, effective problem solving is often about operating at the right level, or the right scale. The cell feels like appropriate level at which to interrogate many of the diseases that ail us, because the senses that guide our own perceptions of sickness and health—the smoldering pain of inflammation, the tunnel vision of a migraine, the dizziness of a fluttering heart—are emergent.
This, unfortunately, is sort of where Mukherjee leaves the reader, under-exploring the consequences of a biology of emergence. Many practical and profound questions have to do with the ways that each scale of life feeds back on the others. In a tome on Cells and “the future human” I wished that Mukherjee had created more space for seeking the ways that cells will shape and be shaped by the future, of humanity and otherwise.
We are entering a phase of real-world bioengineering that features the modularization of cellular parts within cells, of cells within organs, of organs within bodies, and of bodies within ecosystems. In this reality, we would be unwise to assume that any whole is the mere sum of its parts.
For example, when discussing the regenerative power of pluripotent stem cells, Mukherjee raises the philosophical thought experiment of the Delphic boat, also known as the Ship of Theseus. The boat is made of many pieces of wood, each of which is replaced for repairs over the years, with the boat’s structure unchanged. Eventually none of the boat’s original wood remains: Is it the same boat?
Mukherjee raises the Delphic boat in one paragraph at the end of the chapter on stem cells, as a metaphor related to the possibility of stem cell-enabled regeneration in perpetuity. He does not follow any of the threads of potential answers. Given the current state of cellular engineering, about which Mukherjee is a world expert from his work as a physician-scientist, this book could have used an entire section dedicated to probing this question and, importantly, the ways this thought experiment falls apart.
We are entering a phase of real-world bioengineering that features the modularization of cellular parts within cells, of cells within organs, of organs within bodies, and of bodies within ecosystems. In this reality, we would be unwise to assume that any whole is the mere sum of its parts. Wholeness at any one of these scales of life—organelle, cell, organ, body, ecosystem—is what is at stake if we allow biological reductionism to assume away the relation between those scales.
In other words, Mukherjee succeeds in providing a masterful and compelling narrative of the lives of many of the cells that emerge to enliven us. Like his previous books, it is a worthwhile read for anyone curious about the role of cells in disease and in health. And yet, he fails to offer the broader context of The Song of the Cell.
As leading agronomist and essayist Wes Jackson has written, “The sequence of amino acids that is at home in the human cell, when produced inside the bacterial cell, does not fold quite right. Something about the E. coli internal environment affects the tertiary structure of the protein and makes it inactive. The whole in this case, the E. coli cell, affects the part—the newly made protein. Where is the priority of part now?” [1]
Beyond the ways that different kingdoms of life translate the same genetic code, the practical situation for humanity today relates to the ways that the different disciplines of modern life use values and culture to influence our genes, cells, bodies, and environment. It may be that humans will soon become a bit like the Delphic boat, infused with the buzz of fresh cells to repopulate different niches within our bodies, for healthier, longer lives. But in biology, as in writing, a mixed metaphor can cause something of a cacophony. For we are not boats with parts to be replaced piecemeal. And nor are whales, nor alpine forests, nor topsoil. Life isn’t a sum of parts, and neither is a song that rings true.
[1] Wes Jackson, "Visions and Assumptions," in Nature as Measure (p. 52-53).
My guest today for the Making Sense of Science podcast is Camila dos Santos, associate professor at Cold Spring Harbor Lab, who is a leading researcher of the inner lives of human mammary glands, more commonly known as breasts. These organs are unlike any other because throughout life they undergo numerous changes, first in puberty, then during pregnancies and lactation periods, and finally at the end of the cycle, when babies are weaned. A complex interplay of hormones governs these processes, in some cases increasing the risk of breast cancer and sometimes lowering it. Witnessing the molecular mechanics behind these processes in humans is not possible, so instead Dos Santos studies organoids—the clumps of breast cells donated by patients who undergo breast reduction surgeries or biopsies.
Show notes:
2:52 In response to hormones that arise during puberty, the breast cells grow and become more specialized, preparing the tissue for making milk.
7:53 How do breast cells know when to produce milk? It’s all governed by chemical messaging in the body. When the baby is born, the brain will release the hormone called oxytocin, which will make the breast cells contract and release the milk.
12:40 Breast resident immune cells are including T-cells and B-cells, but because they live inside the breast tissue their functions differ from the immune cells in other parts of the body,
17:00 With organoids—dimensional clumps of cells that are cultured in a dish—it is possible to visualize and study how these cells produce milk.
21:50 Women who are pregnant later in life are more likely to require medical intervention to breastfeed. Scientists are trying to understand the fundamental reasons why it happens.
26:10 Breast cancer has many risks factors. Generic mutations play a big role. All of us have the BRCA genes, but it is the alternation in the DNA sequence of the BRCA gene that can increase the predisposition to breast cancer. Aging and menopause are the risk factors for breast cancer, and so are pregnancies.
29:22 Women that are pregnant before the age of 20 to 25, have a decreased risk of breast cancer. And the hypothesis here is that during pregnancy breast cells more specialized, as specialized cells, they have a limited lifespan. It's more likely that they die before they turn into cancer.
33:08 Organoids are giving scientists an opportunity to practice personalized medicine. Scientists can test drugs on organoids taken from a patient to identify the most efficient treatment protocol.
Links:
Camila dos Santos’s Lab Page.
Editor's note: In addition to being a regular writer for Leaps.org, Lina Zeldovich is the guest host for today's episode of the Making Sense of Science podcast.
Lina Zeldovich has written about science, medicine and technology for Popular Science, Smithsonian, National Geographic, Scientific American, Reader’s Digest, the New York Times and other major national and international publications. A Columbia J-School alumna, she has won several awards for her stories, including the ASJA Crisis Coverage Award for Covid reporting, and has been a contributing editor at Nautilus Magazine. In 2021, Zeldovich released her first book, The Other Dark Matter, published by the University of Chicago Press, about the science and business of turning waste into wealth and health. You can find her on http://linazeldovich.com/ and @linazeldovich.
Podcast: The Friday Five Weekly Roundup in Health Research
The Friday Five covers five stories in research that you may have missed this week. There are plenty of controversies and troubling ethical issues in science – and we get into many of them in our online magazine – but this news roundup focuses on scientific creativity and progress to give you a therapeutic dose of inspiration headed into the weekend.
Here are the promising studies covered in this week's Friday Five:
- Not a fan of breathing in micro plastics? New robot noses could help
- You don't need a near-death experience to get the benefits
- How to tell the difference between good and bad inflammation
- Brain shocks for better memory - don't try this at home (yet)!
- A new way to know if your bum back is getting better
The honorable mention for this week's Friday Five: One activity can increase your longevity even without good genes for living longer.