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Dr. Anna Penn uses a microscope

New model mimics persistent interneuron loss seen in prematurity

Dr. Anna Penn uses a microscope

Children’s research-clinicians created a novel preclinical model that mimics the persistent interneuron loss seen in preterm human infants, identifying interneuron subtypes that could become future therapeutic targets to prevent or lessen neurodevelopmental risks.

Research-clinicians at Children’s National Health System have created a novel preclinical model that mimics the persistent interneuron loss seen in preterm human infants, identifying interneuron subtypes that could become future therapeutic targets to prevent or lessen neurodevelopmental risks, the team reports Jan. 31, 2019, in eNeuro. The open access journal for Society for Neuroscience recognized the team’s paper as its “featured” article.

In the prefrontal cortex (PFC) of infants born preterm, there are decreased somatostatin and calbindin interneurons seen in upper cortical layers in infants who survived for a few months after preterm birth. This neuronal damage was mimicked in an experimental model of preterm brain injury in the PFC, but only when the newborn experimental models had first experienced a combination of prenatal maternal immune activation and postnatal chronic sublethal hypoxia. Neither neuronal insult on its own produced the pattern of interneuron loss in the upper cortical layers observed in humans, the research team finds.

“These combined insults lead to long-term neurobehavioral deficits that mimic what we see in human infants who are born extremely preterm,” says Anna Penn, M.D., Ph.D., a neonatologist in the Division of Neonatology and the Fetal Medicine Institute and a developmental neuroscientist at Children’s National Health System, and senior study author. “Future success in preventing neuronal damage in newborns relies on having accurate experimental models of preterm brain injury and well-defined outcome measures that can be examined in young infants and experimental models of the same developmental stage.”

According to the Centers for Disease Control and Prevention 1 in 10 infants is born preterm, before the 37th week of pregnancy. Many of these preterm births result from infection or inflammation in utero. After delivery, many infants experience other health challenges, like respiratory failure. These multi-hits can exacerbate brain damage.

Prematurity is associated with significantly increased risk of neurobehavioral pathologies, including autism spectrum disorder and schizophrenia. In both psychiatric disorders, the prefrontal cortex inhibitory circuit is disrupted due to alterations of gamma-aminobutyric acid (GABA) interneurons in a brain region involved in working memory and social cognition.

Cortical interneurons are created and migrate late in pregnancy and early infancy. That timing leaves them particularly vulnerable to insults, such as preterm birth.

In order to investigate the effects of perinatal insults on GABAergic interneuron development, the Children’s research team, led by Helene Lacaille, Ph.D., in Dr. Penn’s laboratory, subjected the new preterm encephalopathy experimental model to a battery of neurobehavioral tests, including working memory, cognitive flexibility and social cognition.

“This translational study, which examined the prefrontal cortex in age-matched term and preterm babies supports our hypothesis that specific cellular alterations seen in preterm encephalopathy can be linked with a heightened risk of children experiencing neuropsychiatric disorders later in life,” Dr. Penn adds. “Specific interneuron subtypes may provide specific therapeutic targets for medicines that hold the promise of preventing or lessening these neurodevelopmental risks.”

In addition to Dr. Penn and Lead Author Lacaille, Children’s co-authors include Claire-Marie Vacher; Dana Bakalar, Jiaqi J. O’Reilly and Jacquelyn Salzbank, all of Children’s Center for Neuroscience Research.

Financial support for research described in this post was provided by the National Institutes of Health under award R01HD092593, District of Columbia Intellectual Developmental Disabilities Research Center under award U54HD090257, Cerebral Palsy Alliance Research Foundation, Children’s National Board of Visitors, Children’s Research Institute and Fetal Medicine Institute.

DNA moleucle

PAC1R mutation may be linked to severity of social deficits in autism

DNA moleucle

A mutation of the gene PAC1R may be linked to the severity of social deficits experienced by kids with autism spectrum disorder (ASD), finds a study from a multi-institutional research team led by Children’s National faculty. If the pilot findings are corroborated in larger, multi-center studies, the research published online Dec. 17, 2018, in Autism Research represents the first step toward identifying a potential novel biomarker to guide interventions and better predict outcomes for children with autism.

As many as 1 in 40 children are affected by ASD. Symptoms of the disorder – such as not making eye contact, not responding to one’s name when called, an inability to follow a conversation of more than one speaker or incessantly repeating certain words or phrases – usually crop up by the time a child turns 3.

The developmental disorder is believed to be linked, in part, to disrupted circuitry within the amygdala, a brain structure integral for processing social-emotional information. This study reveals that PAC1R is expressed during key periods of brain development when the amygdala – an almond-shaped cluster of neurons – develops and matures. A properly functioning amygdala, along with brain structures like the prefrontal cortex and cerebellum, are crucial to neurotypical social-emotional processing.

“Our study suggests that an individual with autism who is carrying a mutation in PAC1R may have a greater chance of more severe social problems and disrupted functional brain connectivity with the amygdala,” says Joshua G. Corbin, Ph.D., interim director of the Center for Neuroscience Research at Children’s National Health System and the study’s co-senior author. “Our study is one important step along the pathway to developing new biomarkers for autism spectrum disorder and, hopefully, predicting patients’ outcomes.”

The research team’s insights came through investigating multiple lines of evidence:

  • They looked at gene expression in the brains of an experimental model at days 13.5 and 18.5 of fetal development and day 7 of life, dates that correspond with early, mid and late amygdala development. They confirmed that Pac1r is expressed in the experimental model at a critical time frame for brain development that coincides with the timing for altered brain trajectories with ASD.
  • They looked at gene expression in the human brain by mining publicly available genome-wide transcriptome data, plotting median PAC1R expression values for key brain regions. They found high levels of PAC1R expression at multiple ages with higher PAC1R expression in male brains during the fetal period and higher PAC1R expression in female brains during childhood and early adulthood.
  • One hundred twenty-nine patients with ASD aged 6 to 14 were recruited for behavioral assessment. Of the 48 patients who also participated in neuroimaging, 20 were able to stay awake for five minutes without too much movement as the resting state functional magnetic resonance images were captured. Children who were carriers of the high-risk genotype had higher resting-state connectivity between the amygdala and right posterior temporal gyrus. Connectivity alterations in a region of the brain involved in processing visual motion may influence how kids with ASD perceive socially meaningful information, the authors write.
  • Each child also submitted a saliva sample for DNA genotyping. Previously published research finds that a G to C single nucleotide polymorphism, a single swap in the nucleotides that make up DNA, in PAC1R is associated with higher risk for post traumatic stress disorder in girls. In this behavioral assessment, the research team found children with autism who carried the homozygous CC genotype had higher scores as measured through a validated tool, meaning they had greater social deficits than kids with the heterozygous genotype.

All told, the project is the fruit of six years of painstaking research and data collection, say the researchers. That includes banking patients’ saliva samples collected during clinical visits for future retrospective analyses to determine which genetic mutations were correlated with behavioral and functional brain deficits, Corbin adds.

Lauren Kenworthy, who directs our Center for Autism Spectrum Disorders, and I have been talking over the years about how we could bring our programs together. We homed in on this project to look at about a dozen genes to assess correlations and brought in experts from genetics and genomics at Children’s National to sequence genes of interest,” he adds. “Linking the bench to bedside is especially difficult in neuroscience. It takes a huge amount of effort and dozens of discussions, and it’s very rare. It’s an exemplar of what we strive for.”

In addition to Corbin, study co-authors include Lead Author Meredith Goodrich and Maria Jesus Herrero, post-doctoral fellow, Children’s Center for Neuroscience Research; Anna Chelsea Armour and co-Senior Author Lauren Kenworthy, Ph.D., Children’s Center for Autism Spectrum Disorders; Karuna Panchapakesan, Joseph Devaney and Susan Knoblach, Ph.D., Children’s Center for Genetic Medicine Research; Xiaozhen You and Chandan J. Vaidya, Georgetown University; and Catherine A.W. Sullivan and Abha R. Gupta, Yale School of Medicine.

Financial support for the research described in this report was provided by DC-IDDRC under awards HD040677-07 and 1U54HD090257, the Clinical and Translational Science Institute at Children’s National, The Isidore and Bertha Gudelsky Family Foundation and the National Institutes of Health under awards MH083053-01A2 and MH084961.