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little girl with spina bifida

Oral clefts may stem from a shared genetic cause as neural tube defects

little girl with spina bifida

Research by an international team that includes Children’s National faculty, published online Jan. 25, 2019 in Human Molecular Genetics, suggests that genetic mutations that cause cleft lip and palate also may contribute to neural tube defects, such as spina bifida.

Oral clefts are some of the most common birth defects worldwide, affecting about one in every 700 births. In the U.S., more than 4,000 babies are born each year with cleft lip, with or without cleft palate.

This defect isn’t simply a cosmetic manner: Oral clefts can severely affect feeding, speech and hearing, and they cause about 3,300 deaths annually worldwide.

To better understand these conditions, researchers have isolated a number of genetic mutations that appear to play contributing roles. These include those in a gene known as Interferon Regulatory Factor 6. New research by an international team that includes Children’s National faculty, published online Jan. 25, 2019 in Human Molecular Genetics, suggests that these mutations also may contribute to neural tube defects such as spina bifida.

In the first weeks of fetal development, the neural plate curves, creating a neural tube that, once fused shut, becomes the fetal brain and fetal spinal cord. Neural tube defects, which can range from mild to severe, are characterized by incomplete development of the brain, spinal cord or meninges. These defects can potentially result in paralysis or even fetal or neonatal demise. According to the National Institutes of Health, spina bifida, which affects the spinal cord, is the most common neural tube defect in the U.S., affecting up to 2,000 infants each year.

“Despite its high frequency, spina bifida remains among the least understood structural birth defects,” says Brian C. Schutte, an associate professor of Microbiology and Molecular Genetics, Pediatrics and Human Development at Michigan State University and the study’s senior author. “There is strong evidence that genetic factors are a leading cause of such structural birth defects, but in most cases, the cause is unknown. Our team’s study is the first published research to demonstrate that DNA variants in the gene IRF6 can cause spina bifida,” Schutte says.

What’s more, the research team identified a mechanism to explain how altering IRF6 leads to neural tube defects. This mechanism links IRF6 function to two other genes – known as transcription Factor AP2A (TFAP2A) and Grainyhead Like 3 (GRHL3) – that are also known to be required for the development of the neural tube, lip and palate.

“We’re all on the hunt for the reasons when, how and why birth defects happen,” adds Youssef A. Kousa, MS, D.O., Ph.D., a clinical fellow in the Division of Child Neurology at Children’s National Health System and the study’s lead author. “Our main goal is prevention. This paper is a significant development because our team has identified a group of genes that can potentially contribute to very common types of birth defects: craniofacial as well as neural tube defects.”

The scientific odyssey is a wonderful example of serendipity. Kousa, then working in Schutte’s lab, was studying the effects of a new mutant experimental model strain on development of the palate. But one day, he walked into Schutte’s office holding a deformed preclinical embryo and said: “Brian, look at this!”

“Weird things happen in biology,” Schutte replied and counseled him to return if it happened again. Less than two weeks later, Kousa was back with several more of the deformed preclinical embryos, saying: “OK, Brian. It happened again.”

Within hours Kousa had unearthed recently published research that included an image of a similarly affected preclinical embryo. The pair then sketched out possible intersecting genetic pathways, as they brainstormed the myriad ways to end up with that specific phenotype. Initially, they tested their hypotheses in experimental models and eventually corroborated findings through human genetic studies.

The human studies could only be performed by collaborations. Schutte shared their initial observations with human genetics researchers scattered across the country. Those labs then generously agreed to test whether DNA variants in IRF6 were associated with neural tube defects in samples from patients that they had collected over decades of research.

The team found that Tfap2aIrf6 and Grhl3 are components of a gene regulatory network required for neurulation, a folding process that results in the neural tube bending and then fusing to become the basis of the embryo’s nervous system, from brain to spinal cord.

“Since this network is also required for formation of the lip, palate, limbs and epidermis, which develop at different times and places during embryogenesis, we suggest that the Tfap2aIrf6Grhl3 network is a fundamental pathway for multiple morphogenetic processes,” the researchers write.

Interferon Regulatory Factor 6 functions best when there is neither too much expression nor too little. Overexpression of Irf6 suppresses Transcription Factor Activation Protein 2A and Grainyhead Like 3, causing exencephaly, a neural tube defect characterized by the brain being located outside of the skull. Counterintuitively, experimental models that had too little Irf6 also ended up with reduced levels of Tfap2a and Grhl3 that led to a structural birth defect, but at the opposite end of the neural tube.

To test whether the experimental model findings held true in humans, they sequenced samples from people who had spina bifida and anencephaly – the rare birth defect that Kousa spotted in the experimental models – and found IRF6 function was conserved in people. Because of the genetic complexity of these birth defects, and the challenges inherent in collecting samples from cases of severe birth defects, many research teams were invited to participate in the study.

As testament to their collegiality, researchers from Stanford University, University of Texas at Austin, University of Iowa, University of Texas at Houston and Duke University agreed to share precious samples from the California Birth Defects Monitoring Program, from the Hereditary Basis of Neural Tube Defects study and from their own institutional sample collections.

“As we get better at personalized medicine, we could use this information to one day help to counsel families about their own risk and protective factors,” Kousa adds. “If we can identify the genetic pathway, we might also be able to modify it to prevent a birth defect. For example, prenatal supplementation with folic acid has led to a decrease in babies born with neural tube defects, but not all neural tube defects are sensitive to folic acid. This knowledge will help us develop individual-based interventions.”

Financial support for the research covered in this post was provided by the National Institutes of Health under grants DE13513, F31DE022696, DE025060, P01HD067244 and GM072859; startup funding from Michigan State University and the UT-Health School of Dentistry in Houston; and the Centers for Disease Control and Prevention under award number 5U01DD001033.

In addition to Kousa and Schutte, study co-authors include Huiping Zhu, Yunping Lei and Richard H. Finnell, University of Texas at Austin; Walid D. Fakhouri, University of Texas Health Science Center at Houston; Akira Kinoshita, Nagasaki University; Raeuf R. Roushangar, Nicole K. Patel, Tamer Mansour, Arianna L. Smith, and Dhruv B. Sharma, Michigan State University; A.J. Agopian and Laura E. Mitchell, University of Texas School of Public Health; Wei Yang and Gary M. Shaw, Stanford University School of Medicine; Elizabeth J. Leslie, Emory University; Xiao Li, Tamara D. Busch, Alexander G. Bassuk and Brad A. Amendt, University of Iowa; Edward B. Li and Eric C. Liao, Massachusetts General Hospital; Trevor J. Williams, University of Colorado Denver at Anschutz Medical Campus; Yang Chai, University of Southern California; and Simon Gregory and Allison Ashley-Koch, Duke University Medical Center.

banner year

2017: A banner year for innovation at Children’s National

banner year

In 2017, clinicians and research faculty working at Children’s National Health System published more than 850 research articles about a wide array of topics. A multidisciplinary Children’s Research Institute review group selected the top 10 articles for the calendar year considering, among other factors, work published in high-impact academic journals.

“This year’s honorees showcase how our multidisciplinary institutes serve as vehicles to bring together Children’s specialists in cross-cutting research and clinical collaborations,” says Mark L. Batshaw, M.D., Physician-in-Chief and Chief Academic Officer at Children’s National. “We’re honored that the National Institutes of Health and other funders have provided millions in awards that help to ensure that these important research projects continue.”

The published papers explain research that includes using imaging to describe the topography of the developing brains of infants with congenital heart disease, how high levels of iron may contribute to neural tube defects and using an incisionless surgery method to successfully treat osteoid osteoma. The top 10 Children’s papers:

Read the complete list.

Dr. Batshaw’s announcement comes on the eve of Research and Education Week 2018 at Children’s National, a weeklong event that begins April 16, 2018. This year’s theme, “Diversity powers innovation,” underscores the cross-cutting nature of Children’s research that aims to transform pediatric care.

foods rich in folate

An ironclad way to prevent neural tube defects? Not yet

foods rich in folate

Researchers have known for decades that folate, a vitamin enriched in dark, leafy vegetables; fruit; nuts; and other food sources, plays a key role in preventing neural tube defects.

Every year, about 3,000 pregnancies in the U.S. are affected by neural tube defects (NTDs) –  birth defects of the brain, spine and spinal cord. These include anencephaly, in which a major part of the brain, skull and scalp is missing; and spina bifida, in which the backbone and membranes around the spinal cord don’t close properly during fetal development. These structural birth defects can have devastating effects: In the best cases, they might lead to mild but lifelong disability; in the worst cases, babies don’t survive.

Researchers have known for decades that folate, a vitamin enriched in dark, leafy vegetables; fruit; nuts; and other food sources, plays a key role in preventing NTDs. To help get more folate into pregnant women’s diets, wheat flour in the U.S. and many other countries is often fortified with folic acid, a synthetic version of this vitamin, as part of an intervention credited with significantly reducing the incidence of NTDs.

But folic acid supplementation isn’t enough, says Irene E. Zohn, Ph.D., a principal investigator at the Center for Neuroscience Research at Children’s National Health System who studies how genes and the environment interact during development. A significant number of NTDs still occur, suggesting that other approaches – potentially, other nutrients in the maternal diet – might provide further protection.

That’s why Zohn and colleagues decided to investigate iron. Iron deficiency is one of the most common micronutrient deficiencies in women of childbearing age, Zohn explains. Additionally, iron and folate deficiencies often overlap and signal overall poor maternal diets.

The idea that iron deficiency might play a role in NTDs came from studies by Zohn and colleagues of the flatiron mutant line of experimental models. This experimental model line has a mutation in a gene that transports iron across cell membranes, including the cells that supply embryos with this critical micronutrient.

To determine if NTDs develop in these mutant experimental models because of reduced iron transport, the researchers devised a simple experiment: They took female adult experimental models with the mutation and separated them into four groups. For several weeks, one group ate a diet that was high in folic acid. Another group ate a diet high in iron. The third group ate a diet high in both folic acid and iron. The fourth group ate standard chow. All of these experimental models then became pregnant with embryos that harbored the flatiron mutation, and the researchers assessed the offspring for the presence of NTDs.

Irene Zohn

“We were hoping that iron supplements would be the next folic acid, but it did not turn out that way,” says Irene E. Zohn, Ph.D. “Even though our results demonstrate that iron is important for proper neural tube development, giving extra iron definitely has its downsides.”

As they reported in Birth Defects Research, the dietary interventions successfully increased iron stores: Experimental model mothers whose diets were supplemented with iron, folic acid or both had increased concentrations of these micronutrients in their blood.

The dietary interventions also affected their offspring. While about 80 percent of flatiron mutant embryos fed a standard diet during pregnancy had NTDs, feeding a diet high in iron prevented NTDs in half of the offspring. This lower rate was similar in the offspring of mothers fed a diet high in both folic acid and iron, but not for those whose mothers ate just a diet high in folic acid. Those embryos had NTD rates as high as those who ate just the standard chow, suggesting that low iron was the cause of the high rates, not low folic acid.

Together, Zohn says, these experiments show that iron plays an important role in the development of the neural tube and that deficits in iron might cause some cases of NTDs. However, she notes, reducing NTDs isn’t nearly as simple as supplementing pregnant women’s diets with iron. In the same study, the researchers found that when they gave normal experimental models that didn’t have the flatiron mutation concentrated iron supplements – amounts akin to what doctors might prescribe for human patients with very severe iron-deficiency anemia – folate stores dropped.

That’s because these two micronutrients interact in the body with similar sites for absorption and storage in the intestines and liver, Zohn explains. At either the intestines or liver or at both locations, an iron overload might interfere with the body’s ability to absorb or use folate.

At this point, she says, giving high doses of iron routinely during pregnancy doesn’t look like a feasible way to prevent NTDs.

“We were hoping that iron supplements would be the next folic acid, but it did not turn out that way,” Zohn says. “Even though our results demonstrate that iron is important for proper neural tube development, giving extra iron definitely has its downsides.”

Zohn’s team plans to continue to investigate the role of iron, as well as the role of other micronutrients that might influence neural tube development.

Zohn’s coauthors include Bethany A. Stokes, The George Washington University, and Julia A. Sabatino, Children’s National.

Research reported in this story was supported by a grant from the Board of Visitors, Eunice Kennedy Shriver National Institute of Child Health & Human Development under award number R21-HD076202, the National Center for Research Resources under award number UL1RR031988, Children’s Research Institute and the National Institutes of Health under grant P30HD040677.