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Andrea Gropman

$5M in federal funding to help patients with urea cycle disorders

Andrea Gropman

Andrea L. Gropman, M.D.: We have collected many years of longitudinal clinical data, but with this new funding now we can answer questions about these diseases that are meaningful on a day-to-day basis for patients with urea cycle disorders.

An international research consortium co-led by Andrea L. Gropman, M.D., at Children’s National Hospital has received $5 million in federal funding as part of an overall effort to better understand rare diseases and accelerate potential treatments to patients.

Urea cycle disorder, one such rare disease, is a hiccup in a series of biochemical reactions that transform nitrogen into a non-toxic compound, urea. The six enzymes and two carrier/transport molecules that accomplish this essential task reside primarily in the liver and, to a lesser degree, in other organs.

The majority of patients have the recessive form of the disorder, meaning it has skipped a generation. These kids inherit one copy of an abnormal gene from each parent, while the parents themselves were not affected, says Dr. Gropman, chief of the Division of Neurodevelopmental Pediatrics and Neurogenetics at Children’s National. Another more common version of the disease is carried on the X chromosome and affects boys more seriously that girls, given that boys have only one X chromosome.

Regardless of the type of urea cycle disorder, when the urea cycle breaks down, nitrogen converts into toxic ammonia that builds up in the body (hyperammonemia), particularly in the brain. As a result, the person may feel lethargic; if the ammonia in the bloodstream reaches the brain in high concentrations, the person can experience seizures, behavior changes and lapse into a coma.

Improvements in clinical care and the advent of effective medicines have transformed this once deadly disease into a more manageable chronic ailment.

“It’s gratifying that patients diagnosed with urea cycle disorder now are surviving, growing up, becoming young adults and starting families themselves. Twenty to 30 years ago, this never would have seemed conceivable,” Dr. Gropman says. “We have collected many years of longitudinal clinical data, but with this new funding now we can answer questions about these diseases that are meaningful on a day-to-day basis for patients with urea cycle disorders.”

In early October 2019, the National Institutes of Health (NIH) awarded the Urea Cycle Disorders Consortium for which Dr. Gropman is co-principal investigator a five-year grant. This is the fourth time that the international Consortium of physicians, scientists, neuropsychologists, nurses, genetic counselors and researchers has received NIH funding to study this group of conditions.

Dr. Gropman says the current urea cycle research program builds on a sturdy foundation built by previous principal investigators Mendel Tuchman, M.D., and Mark Batshaw, M.D., also funded by the NIH. While previous rounds of NIH funding powered research about patients’ long-term survival prospects and cognitive dysfunction, this next phase of research will explore patients’ long-term health.

Among the topics they will study:

Long-term organ damage. Magnetic resonance elastrography (MRE) is a state-of-the-art imaging technique that combines the sharp images from MRI with a visual map that shows body tissue stiffness. The research team will use MRE to look for early changes in the liver – before patients show any symptoms – that could be associated with long-term health impacts. Their aim is spot the earliest signs of potential liver dysfunction in order to intervene before the patient develops liver fibrosis.

Academic achievement. The research team will examine gaps in academic achievement for patients who appear to be underperforming to determine what is triggering the discrepancy between their potential and actual scholastics. If they uncover issues such as learning difficulties or mental health concerns like anxiety, there are opportunities to intervene to boost academic achievement.

“And if we find many of the patients meet the criteria for depression or anxiety disorders, there are potential opportunities to intervene.  It’s tricky: We need to balance their existing medications with any new ones to ensure that we don’t increase their hyperammonemia risk,” Dr. Gropman explains.

Neurologic complications. The researchers will tap continuous, bedside electroencephalogram, which measures the brain’s electrical activity, to detect silent seizures and otherwise undetectable changes in the brain in an effort to stave off epilepsy, a brain disorder that causes seizures.

“This is really the first time we will examine babies’ brains,” she adds. “Our previous imaging studies looked at kids and adults who were 6 years and older. Now, we’re lowering that age range down to infants. By tracking such images over time, the field has described the trajectory of what normal brain development should look like. We can use that as a background and comparison point.”

In the future, newborns may be screened for urea cycle disorder shortly after birth. Because it is not possible to diagnose it in the womb in cases where there is no family history, the team aims to better counsel families contemplating pregnancy about their possible risks.

Research described in this post was underwritten by the NIH through its Rare Diseases Clinical Research Network.

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X-linked genes help explain why boys of all ages face higher respiratory risk

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A multi-institution research team that includes Children’s National Health System attempted to characterize gender-based epigenomic signatures in the human airway early in children’s lives with a special attention to defining DNA methylation patterns of the X chromosome.

Human airways already demonstrate gender-based differences in DNA methylation signatures at birth, providing an early hint of which infants may be predisposed to develop respiratory disorders like asthma later in life, a research team reports in a paper published online April 3, 2018, in Scientific Reports.

It’s clear that boys and young men are more likely to develop neonatal respiratory distress syndrome, bronchopulmonary dysplasia, viral bronchiolitis, pneumonia, croup and childhood asthma. Unlike boys, girls have an additional copy of the X chromosome, which is enriched with immune-related genes, some of which play key roles in the development of respiratory conditions. Methylation prevents excessive gene activity in X-linked genes, however much remains unknown about how this process influences infants’ risk of developing airway diseases.

A multi-institution research team that includes Children’s National Health System attempted to characterize gender-based epigenomic signatures in the human airway early in children’s lives with a special attention to defining DNA methylation patterns of the X chromosome.

“It’s clear as we round in the neonatal intensive care unit that baby boys remain hospitalized longer than girls and that respiratory ailments are quite common. Our work provides new insights about gender differences in airway disease risk that are pre-determined by genetics,” says Gustavo Nino, M.D., a Children’s pulmonologist and the study’s senior author.

“Characterizing early airway methylation signatures holds the promise of clarifying the nature of gender-based disparities in respiratory disorders and could usher in more personalized diagnostic and therapeutic approaches.”

The research team enrolled 12 newborns and infants in the study and obtained their nasal wash samples. Six of the infants were born preterm, and six were born full term. The researchers developed a robust gender classification algorithm to generate DNA methylation signals. The machine learning algorithm identified X-linked genes with significant differences in methylation patterns in boys, compared with girls.

As a comparison group, they retrieved pediatric nasal airway epithelial cultures from a study that looked at genomic DNA methylation patterns and gene expression in 36 children with persistent atopic asthma compared with 36 heathy children.

The team went on to classify X-linked genes that had significant gender-based X methylation and those genes whose X methylation was variable.

“These results confirm that the X chromosome contains crucial information about gender-related genetic differences in different airway tissues,” Dr. Nino says. “More detailed knowledge of the genetic basis for gender differences in the respiratory system may help to predict, prevent and treat respiratory disorders that can affect patients over their entire lifetimes.”

In addition to Dr. Nino, study co-authors include Lead Author Cesar L. Nino, bioinformatics scientist, Pontificia Universidad Javeriana; Geovanny F. Perez, M.D., co-director of Children’s Severe Bronchopulmonary Dysplasia Program; Natalia Isaza Brando, M.D., Children’s neonatology attending; Maria J. Gutierrez, Johns Hopkins University School of Medicine; and Jose L. Gomez, Yale University School of Medicine.

Financial support for this research was provided by the National Institutes of Health under award numbers
AI130502-01A1, HL090020, HL125474-03, HD001399, UL1TR000075 and KL2TR000076.