Author: Kat J. McAlpine

Creating custom brains from the ground up

building a custom brain
(ADOBE STOCK)

Scientists studying how genetics impact brain disease have long sought a better experimental model. Cultures of genetically-modified cell lines can reveal some clues to how certain genes influence the development of psychiatric disorders and brain cancers. But such models cannot offer the true-to-form look at brain function that can be provided by genetically-modified mice.

Even then, carefully breeding mice to study how genes impact the brain has several drawbacks. The breeding cycles are lengthy and costly, and the desired gene specificity can only be verified — but not guaranteed — when mouse pups are born.

In today’s Nature, scientists from Boston Children’s Hospital and UC San Francisco describe a new way to create customized mouse models for studying the brain.

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Super suppressor: Boosting a gene that stifles tumor growth

Researchers have packaged a tumor suppressor into a therapeutic nanoparticle.
Researchers have packaged a tumor suppressor into a therapeutic nanoparticle. IMAGE: ISLAM, ET AL.

Most of the time, cancer cells do a combination of two things: they overexpress genes that drive tumor growth and they lose normal genes that typically suppress tumors. No two tumors are exactly alike, but some combination of these two effects is usually what results in cancer. Now, for the first time, researchers have shown that it’s possible to treat cancer by delivering a gene that naturally suppresses tumors.

Researchers from Boston Children’s Hospital, Brigham and Women’s Hospital and Memorial Sloan Kettering Cancer Center combined their cancer biology and nanomaterials expertise and developed a therapeutic capable of delivering a tumor suppressor gene known as PTEN, the loss of which can allow tumors to grow unchecked.

In several preclinical models, their PTENboosting therapeutic was able to inhibit tumor growth. Their findings were published yesterday in Nature Biomedical Engineering.

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Self-sacrificing cells hold clues to improving treatment of MRSA, sepsis

Image of neutrophils
During infection, white blood cells called neutrophils eject their own DNA strands outward to block bacteria from spreading. IMAGE: ADOBE STOCK

Over the last several years, scientists have made great headway in our understanding of how self-sabotaging immune cells play a role in our ability to fight infection. So far, we know that when white blood cells called neutrophils are triggered by bacterial infection, they self-combust and eject their own DNA strands outward like spider webs. Sacrificing themselves, the exploded neutrophils and their outreaching DNA tentacles form sunburst-shaped neutrophil extracellular traps (NETs).

“NET formation is an innate immune response that our body has when it recognizes the presence of pathogens,” says Ben Croker, PhD, a researcher in the Division of Hematology/Oncology at Boston Children’s Hospital. “Once formed, NETs restrict pathogen movement and proliferation and alert the rest of the immune system to the invader’s presence.”

Now, Croker and a team of researchers at Boston Children’s have identified a critical element of NET formation and how it enables the body to fight off infections like methicillin-resistant Staphylococcus aureus (MRSA). Their findings, recently published in Science Signaling, could someday have clinical implications for tough-to-treat infections and even sepsis.

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Blood filtration device could provide personalized care for sepsis

Artistic image of cytokines
Could cell-signaling proteins called cytokines be modulated to tame inflammation? IMAGE: ADOBE STOCK

Cytokines are small proteins produced by the body’s cells that have a big impact on our immune system. Researchers at Boston Children’s Hospital believe that modulating their presence in our bodies could be the key to improving outcomes in life-threatening cases of trauma, hemorrhage and many other conditions including sepsis, which alone impacts nearly one million Americans each year.

The reason? Cells essentially use cytokines to talk to one another. In response to their surroundings, cells release different types of cytokines that encourage inflammatory or anti-inflammatory effects on the body. Infection or trauma causes cells to pump out more cytokines that produce inflammation. Altogether, an escalating chorus of cytokines can sometimes tip a person’s body into overwhelming inflammation that can turn fatal, which is what happens during sepsis.

But what if scientists could remove the problematic cytokines to bring the choir into perfect tune, allowing the immune system to respond with just the right amount of inflammation for healing?

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Why are males more prone to bladder cancer than females?

A microscopic view of human testis tissue. Researchers have discovered why males are more likely to get bladder cancer than females.
A microscopic view of human testis tissue. Researchers have discovered why males are more likely to get bladder cancer than females. IMAGE: ADOBE STOCK

New research helps explain why men are three to five times more likely to develop bladder cancer than women.

Using mouse models and human patient data, Boston Children’s Hospital researchers in the urology department, Xue Sean Li, PhD, and Satoshi Kaneko, PhD, found that inherent genomic differences contribute to the contrast in bladder cancer rate between males and females.

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A perfect genetic hit: New gene mutation implicated in rare congenital diarrhea

Normal intestinal organoids (left) in contrast to intestinal organoids derived from patients (right) with a newly-discovered gene mutation linked to congenital diarrhea.
Normal intestinal organoids (left) in contrast to intestinal organoids derived from patients (right) with a newly-discovered gene mutation linked to congenital diarrhea.

When the 1-year-old boy arrived from overseas, he was relying on total parenteral nutrition — a way of bypassing the digestive system to provide nutrients and calories completely intravenously — to survive. From the time of his birth, he had experienced unexplainable diarrhea. Answers were desperately needed.

Sequencing his genes in search of clues, neonatologists and collaborators at the Manton Center for Orphan Disease Research at Boston Children’s Hospital identified a new gene mutation responsible for chronic congenital diarrhea — even finding a similar mutation in two other children as well.

Using patient-derived intestinal organoids in the laboratory, the team discovered that the newly-identified gene mutation, WNT2B, appears to stifle intestinal stem cells’ normal function and growth. The findings were published in the American Journal of Human Genetics.

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“Teenage” red blood cells could hold the key to a malaria vaccine

A T cell (right) launches an attack on an immature red blood cell called a reticulocyte. This immune response could help design a malaria vaccine.
A T cell (right) launches an attack on an immature red blood cell (left) infected with a malaria parasite called P. vivax. At the arrow, the T cell breaches the infected cell’s membrane to deliver death-inducing enzymes. Credit: Lieberman lab/Boston Children’s Hospital

Malaria parasite infection, which affects our red blood cells, can be fatal. Currently, there are about 200 million malaria infections in the world each year and more than 400,000 people, mostly children, die of malaria each year.

Now, studying blood samples from patients treated for malaria at a clinical field station in Brazil’s Amazon jungle, a team of Brazilian and American researchers has made a surprising discovery that could open the door to a new vaccine.

“I noticed that white blood cells called killer T cells were activated in response to malaria parasite infection of immature red blood cells,” says Caroline Junqueira, PhD, a visiting scientist at Boston Children’s Hospital and Harvard Medical School (HMS).

For red blood cells, this activity is unusual.

“Infected red blood cells aren’t recognized by our immune system’s T cells in the same way that most other infected cells of the human body are,” says Judy Lieberman, MD, PhD, chair in the Program in Cellular and Molecular Medicine at Boston Children’s Hospital.

Digging deeper, Junqueira, Lieberman and collaborators have found a completely unexpected immune response to malaria parasites that infect immature blood cells called reticulocytes. The revelation could help to design a new vaccine that might be capable of preventing malaria.

Their findings, published today in Nature Medicineuncover special cellular mechanisms and properties specific to “teenaged” reticulocytes and a strain of malaria called Plasmodium vivax that enable our T cells to recognize and destroy both the infected reticulocytes and the parasites inside them.

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A huge leap for cloning

Two identical mice are pictured. Researchers have reported a new technique to improve mouse cloning efficiency.Animal cloning, the creation of a genetically identical copy of an individual organism, holds promise for many different reasons, including its use to conserve endangered species and to improve our understanding of developmental biology, which could eventually help us prevent or reverse developmental disorders from the get-go. Although more than 20 species of animals have been cloned so far, cloning efficiency, or the percent of successful live births, has remained universally low and economically out of reach for most practical applications.

But now, researchers at Boston Children’s Hospital have reported a new cloning technique that has yielded the highest efficiency ever reported in mouse cloning, capable of producing 13 to 16 times more mouse pups than previous methods. The findings were reported in Cell Stem Cell.

To improve mouse cloning efficiency, a team led by the study’s senior author Yi Zhang, PhD, corrected two factors that they had previously identified as having impact on successful development of cloned embryos.

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Getting a grip on genetic loops

Chromatin is housed inside the nucleus. A new discovery about its physical arrangement could pave the way for new therapeutics.
Artist’s rendering of chromatin, which is housed inside the nuclei of mammalian cells. A new discovery about its physical arrangement could pave the way for new therapeutics.

A new discovery about the spatial orientation and physical interactions of our genes provides a promising step forward in our ability to design custom antibodies. This, in turn, could revolutionize the fields of vaccine development and infection control.

“We are beginning to understand the full biological impact that the physical structure and movement of our genes play in regulating health and development,” says Frederick Alt, PhD, director of the Boston Children’s Hospital Program in Cellular and Molecular Medicine (PCMM) and the senior author of the new study, published in the latest issue of Cell.

Recent years of research by Alt and others in the field of molecular biology have revealed that it’s not just our genes themselves that determine health and disease states. It’s also the three-dimensional arrangement of our genes that plays a role in keeping genetic harmony. Failure of these structures may trigger genetic mutations or genome rearrangements leading to catastrophe.

The importance of genetic loops

Crammed inside the nucleus, chromatin, the chains of DNA and proteins that make up our chromosomes, is arranged in extensive loop arrangements. These loop configurations physically confine segments of genes that ought to work together in a close proximity to one another, increasingly their ability to work in tandem.

“All the genes contained inside one loop have a greater than random chance of coming together,” says Suvi Jain, PhD, a postdoctoral researcher in Alt’s lab and a co-first author on the study.

Meanwhile, genes that ought to stay apart remain blocked from reaching each other, held physically apart inside our chromosomes by the loop structures of our chromatin.

But while many chromatin loops are hardwired into certain formations throughout all our cells, it turns out that some types of cells, such as certain immune cells, are more prone to re-arrangement of these loops.

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Hearts get a boost from mitochondrial transplantation

In this artistic rendering, mitochondria (enlarged at top left) are depicted inside heart muscle cells. Watch an animation about mitochondrial transplantation.

For decades, cardiac researcher James McCully, PhD, has been spellbound by the idea of using mitochondria, the “batteries” of the body’s cells, as a therapy to boost heart function. Finally, a clinical trial at Boston Children’s Hospital is bringing his vision — a therapy called mitochondrial transplantation — to life.

Mitochondria, small structures inside all of our cells, synthesize the essential energy that our cells need to function. In the field of cardiac surgery, a well-known condition called ischemia often damages mitochondria and its mitochondrial DNA inside the heart’s muscle cells, causing the heart to weaken and pump blood less efficiently. Ischemia, a condition of reduced or restricted blood flow, can be caused by congenital heart defects, coronary artery disease and cardiac arrest.

For the smallest and most vulnerable patients who are born with severe heart defects, a heart-lung bypass machine called extracorporeal membrane oxygenation (ECMO) can help restore blood flow and oxygenation to the heart. But even after blood flow has returned, the mitochondria and their DNA remain damaged.

“In the very young and the very old, especially, their hearts are not able to bounce back,” says McCully.

Ischemia can be fatal for the tiniest patients

After cardiac arrest, for instance, a child’s mortality rate jumps to above 40 percent because of ischemia’s effects on mitochondria. If a child’s heart is too weak to function without the support of ECMO, his or her risk of dying increases each additional day spent connected to the machine.

But what if healthy mitochondria could come to the rescue and replace the damaged ones?

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