Cold Spring Harbor

You Call It Corn Stem Cells, We Call It An A-Maize-Ing Hope to Feed the World

/ Todd Dubnicoff / Leave a comment
figure_6A

David Jackson and his team at Cold Spring Harbor Laboratory identify a unique genetic pathway that regulated stem cell growth. Certain mutations in the pathway lead to increased plant yields (two plants on the right). Image: Cold Spring Harbor Laboratory

Here at the Stem Cellar, we’re laser-beam focused on the exciting progress being made to bring stem cell-based treatments to patients with unmet medical needs. But what good will those life-saving treatments be if the patients end up starving from hunger? It’s a serious question to ask considering the world’s diminishing farmlands and yet another record-breaking month for global warming in the books.

Based on a study published yesterday by Cold Spring Harbor Laboratory researchers, our friend the stem cell emerges again as a source of hope. Reporting in Nature Genetics, the team uncovered an important genetic switch in the stem cells of corn that when manipulated can lead to a 50% increase in the size of the corn.

Plants have stem cells too
Plants do indeed have stem cells that reside in an area called the meristem and function similarly to their animal counterparts. The root apical meristem is responsible for providing cells for root growth while the shoot apical meristem gives rise to plant organs like leaves and flowers. Previous research had shown that a signal system within the meristem communicates whether or not to turn on stem cell growth. The current study identified protein signals involved in a similar regulatory circuit but with an intriguing difference which David Jackson, the lead author on the study, explained in a Cold Spring Harbor video (see below):

“In this new study we found that actually the leaves, the developing leaves, send a signal back to the stem cells to control their growth which is really a new finding.”

FCP-1/FEA3: A Leaf to Stem Cell Braking System
The proteins involved in this signal include a receptor protein on the stem cells called FEA3 and a protein from the leaves called FCP-1. When it travels from the leaves to the stem cells, FCP-1 binds to FEA3 causing an inhibition of stem cell growth. So you’d think that disrupting this pathway would release the “brake” on stem cell growth and lead to tractor-sized corn. But when the team tested that idea by growing plants with a fea3 mutation, the resulting crop was short and stubby. The explanation is that too many stem cells is not a good thing and the available water, sunlight, and soil is not enough to support increased growth.

Easing off the brakes is better for crop yields
So as a result of uncontrolled stem cell growth, the corn becomes deformed and leads to a poorer yield. But next, the team analyzed plants with weaker versions, or alleles, of the fea3 mutations. Basically, these mutations still lead to a release of the “brake” on stem cell growth but not as quite as much as the initial fea3 mutation. Under this genetic scenario, the plants grew extra rows of kernels with up to 50% increase in yield.

Because the FCP-1/FEA3 pathway is found throughout the plant kingdom, this result has the tantalizing potential to help increase yields of all sorts of food crops.  As Jackson mentions in an interview with Gizmodo, this future will depend on these laboratory experiments working in a real world setting:

“If the yield increases we have seen in our lab strains hold out when used in agricultural maize strains this would lead to a significant boost in yields, potentially improving agricultural sustainability by requiring less land be devoted to agriculture. The same approaches could also benefit farmers in developing countries growing a wide range of crops.”

Certainly this future crop would be considered a genetically modified organism (GMO) which may concern some. But just today the National Academies of Sciences, Engineering, and Medicine posted evidence on their website that points to GMO foods as being safe and good for the environment.

Four Challenges to Making the Best Stem Cell Models for Brain Diseases

/ Karen Ring / Leave a comment

Neurological diseases are complicated. A single genetic mutation causes some, while multiple genetic and environmental factors cause others. Also, within a single neurological disease, patients can experience varying symptoms and degrees of disease severity.

And you can’t just open up the brain and poke around to see what’s causing the problem in living patients. It’s also hard to predict when someone is going to get sick until it’s already too late.

To combat these obstacles, scientists are creating clinically relevant human stem cells in the lab to capture the development of brain diseases and the differences in their severity. However, how to generate the best and most useful stem cell “models” of disease is a pressing question facing the field.

Current state of stem cell models for brain diseases

Cold Spring Harbor Lab, Hillside Campus, Location: Cold Spring Harbor, New York, Architect: Centerbrook Architects

Cold Spring Harbor Lab, Hillside Campus, Location: Cold Spring Harbor, New York, Architect: Centerbrook Architects

A group of expert stem cell scientists met earlier this year at Cold Spring Harbor in New York to discuss the current state and challenges facing the development of stem cell-based models for neurological diseases. The meeting highlighted case studies of recent advances in using patient-specific human induced pluripotent stem cells (iPS cells) to model a breadth of neurological and psychiatric diseases causes and patient symptoms aren’t fully represented in existing human cell models and mouse models.

The point of the meeting was to identify what stem cell models have been developed thus far, how successful or lacking they are, and what needs to be improved to generate models that truly mimic human brain diseases. For a full summary of what was discussed, you can read a Meeting Report about the conference in Stem Cell Reports.

What needs to be done

After reading the report, it was clear that scientists need to address four major issues before the field of patient-specific stem cell modeling for brain disorders can advance to therapeutic and clinical applications.

1. Define the different states of brain cells: The authors of the report emphasized that there needs to be a consensus on defining different cell states in the brain. For instance, in this blog we frequently refer to pluripotent stem cells and neural (brain) stem cells as a single type of cell. But in reality, both pluripotent and brain stem cells have different states, which are reflected by their ability to turn into different types of cells and activate a different set of genes. The question the authors raised was what starting cell types should be used to model specific brain disorders and how do we make them from iPS cells in a reproducible and efficient fashion?

2. Make stem cell models more complex: The second point was that iPS cell-based models need to get with the times. Just like how most action-packed or animated movies come in 3D IMAX, stem cell models also need to go 3D. The brain is comprised of an integrated network of neurons and glial support cells, and this complex environment can’t be replicated on the flat surface of a petri dish.

Advances in generating organoids (which are mini organs made from iPS cells that develop similar structures and cell types to the actual organ) look promising for modeling brain disease, but the authors admit that it’s far from a perfect science. Currently, organoids are most useful for modeling brain development and diseases like microencephaly, which occurs in infants and is caused by abnormal brain development before or after birth. For more complex neurological diseases, organoid technology hasn’t progressed to the point of providing consistent or accurate modeling.

The authors concluded:

“A next step for human iPS cell-based models of brain disorders will be building neural complexity in vitro, incorporating cell types and 3D organization to achieve network- and circuit-level structures. As the level of cellular complexity increases, new dimensions of modeling will emerge, and modeling neurological diseases that have a more complex etiology will be accessible.”

3. Address current issues in stem cell modeling: The third issue mentioned was that of human mosaicism. If you think that all the cells in your body have the same genetic blue print, then you’re wrong. The authors pointed out that as many as 30% of your skin cells have differences in their DNA structure or DNA sequences. Remember that iPS cell lines are derived from a single patient skin or other cell, so the problem is that studies might need to develop multiple iPS cell lines to truly model the disease.

Additionally, some brain diseases are caused by epigenetic factors, which modify the structure of your DNA rather than the genetic sequence itself. These changes can turn genes on and off, and they are unfortunately hard to reproduce accurately when reprogramming iPS cells from patient adult cells.

4. Improve stem cell models for drug discovery: Lastly, the authors addressed the use of iPS cell-based modeling for drug discovery. Currently, different strategies are being employed by academia and industry, both with their pros and cons.

Industry is pursuing high throughput screening of large drug libraries against known disease targets using industry standard stem cell lines. In contrast, academics are pursuing candidate drug screening on a much smaller scale but using more relevant, patient specific stem cell models.

The authors point out that, “a major goal in the still nascent human stem cell field is to utilize improved cell-based assays in the service of small-molecule therapeutics discovery and virtual early-phase clinical trials.”

While in the past, the paths that academia and industry have taken to reach this goal were different, the authors predict a convergence between the paths:

“Now, research strategies are converging, and both types of researchers are moving toward human iPS cell-based screening platforms, drifting toward a hybrid model… New collaborations between academic and pharma researchers promise a future of parallel screening for both targets and phenotypes.”

Conclusions and Looking to the Future

This meeting successfully described the current landscape of iPS cell-based disease modeling for brain disorders and laid out a roadmap for advancing these stem cell models to a stage where they are more effective for understanding the mechanisms behind disease and for therapeutic screening.

I agree with the authors conclusion that:

“Moving forward, a critical application of human iPS cell-based studies will be in providing a platform for defining the cellular, molecular, and genetic mechanisms of disease risk, which will be an essential first step toward target discovery.”

My favorite points in the report were about the need for more collaboration between academia and industry and also the push for reproducibility of these iPS cell models. Ultimately, the goal is to understand what causes neurological disease, and what drugs or stem cell therapies can be used to cure them. While iPS cell models for brain diseases still have a way to go before being more clinically relevant, they will surely play a prominent role in attaining this goal.

Meeting Attendees

Meeting Attendees

Cancer Cells Mimic Blood Vessels to Colonize the Body’s Farthest Reaches

/ cirmweb / Leave a comment

Scientists at Cold Spring Harbor Laboratory have just uncovered the latest dirty trick in the cancer playbook—one that spurs the cancer cells to spread throughout the body and evade treatment. But importantly, they believe they may have found a way to counter it.

Reporting today in the journal Nature, Cold Spring Harbor researchers describe how tumor cells can form tubular networks that mimic blood vessels. It is this mimicry, the team argues, that plays a key role in helping the cancer spread throughout the body—and a significant hurdle to successfully treating the disease.

Two adjacent sections of a mouse breast tumor. Tissue at left is stained so that normal blood vessels can be seen (black arrow). Extending from these vessels are blood filled channels (green arrows). On the right, the tissue is stained for a fluorescent protein expressed by the tumor cells. Here, blood-filled channels are actually formed by tumor cells in a process known as vascular mimicry. [Credit: Hannon Lab, CSHL]

Two adjacent sections of a mouse breast tumor. Tissue at left is stained so that normal blood vessels can be seen (black arrow). Extending from these vessels are blood filled channels (green arrows). On the right, the tissue is stained for a fluorescent protein expressed by the tumor cells. Here, blood-filled channels are actually formed by tumor cells in a process known as vascular mimicry. [Credit: Hannon Lab, CSHL]

Using mouse models of breast cancer, the team—led by Simon Knott—identified this phenomenon, called ‘vascular mimicry,’ and revealed that two genes, called Serpine2 and Slpi, were driving it. Made up of tumor cells literally stacked together, these tubular networks allowed oxygen and other nutrients to reach far-flung tumor cells throughout the body. This kept the tumor cells healthy, and helped them spread.

In today’s press release, Knott explained his initial reactions to this critical discovery:

“It’s very neat to watch and see cells evolve to have these capacities, but on the other hand it’s really scary to think that these cells are sitting there in people doing this.”

In laboratory experiments, the team found that boosting levels of Serpin2 and Slpi boosted the cancer’s ability to build these networks. Conversely, shutting down these two genes appeared to do the opposite. Knott argues that targeting the proteins that these two genes produce, as a way of shutting them off, may be a winning strategy:

“Targeting them might provide therapeutic benefits,” said Knott, “but we’re not sure yet.”

Indeed, research efforts over the past decade or more have tried to curb the production of these tubular networks of tumor cells, but with limited success. These drugs, called angiogenesis inhibitors, may not have worked as well as originally hoped because the underlying mechanism that creates this vascular mimicry—namely the genes Serpin2 and Slpi—was not targeted. Postdoctoral researcher Elvin Wagenblast, the paper’s first author, thinks they might have more success now:

“Maybe by targeting angiogenesis and also vascular mimicry at the same time we might actually have a better benefit in the clinic in the long run.”

This strategy is ultimately the goal of the team, but much work remains. Their most immediate next steps are to understand the process by which tumor cells pass through these tubular networks and infiltrate new areas of the body. But armed with this new-found knowledge of vascular mimicry, these and other researchers may be well on their way to outsmarting cancer, at least some of the time.