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Purkinje cell

Premature birth disrupts Purkinje cell function, resulting in locomotor learning deficits

Purkinje cell

Children’s National Hospital researchers explored how preterm birth disrupts Purkinje cell function, resulting in locomotor learning deficits.

As the care of preterm babies continues to improve, neonatologists face new challenges to ensure babies are protected from injury during critical development of the cerebellum during birth and immediately after birth. How does this early injury affect locomotor function, and to what extent are clinicians able to protect the brain of preterm babies?

A new peer-reviewed study by Aaron Sathyanesan, Ph.D., Panagiotis Kratimenos, M.D., Ph.D., and Vittorio Gallo, Ph.D., published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS), explores exactly what neural circuitry of the cerebellum is affected due to complications that occur around the time of birth causing these learning deficits, and finds a specific type of neurons — Purkinje cells — to play a central role.

Up until now, there has been a sparsity of techniques available to measure neuronal activity during locomotor learning tasks that engage the cerebellum. To surmount this challenge, Children’s National used a multidisciplinary approach, bringing together a team of neuroscientists with neonatologists who leveraged their joint expertise to devise a novel and unique way to measure real-time Purkinje cell activity in a pre-clinical model with clinical relevance to humans.

Researchers measured neural circuit function by pairing GCaMP6f fiber photometry, used to measure neuronal activity in the brain of a free moving subject, with an ErasmusLadder, in which it needs to travel from point A to point B on a horizontal ladder with touch-sensitive rungs that register the type and length of steps. By introducing a sudden obstacle to movement, researchers observed how the subject coped and learned accordingly to avoid this obstacle. By playing a high-pitch tone just before the obstacle was introduced, researchers were able to measure how quickly the subjects were able to anticipate the obstacle and adjust their steps accordingly. Subjects with neonatal brain injury and normal models were run through a series of learning trials while simultaneously monitoring brain activity. In this way, the team was able to quantify cerebellum-dependent locomotor learning and adaptive behavior, unlocking a functional and mechanistic understanding of behavioral pathology that was previously unseen in this field.

In addition to showing that normal Purkinje cells are highly active during movement on the ErasmusLadder, the team explored the question of whether Purkinje cells of injured pre-clinical models were generally non-responsive to any kind of stimuli. They found that while Purkinje cells in injured subjects responded to puffs of air, which generally cue the subject to start moving on the ErasmusLadder, dysfunction in these cells was specific to the period of adaptive learning. Lastly, through chemogenetic inhibition, which specifically silences neonatal Purkinje cell activity, the team was able to mimic the effects of perinatal cerebellar injury, further solidifying the role of these cells in learning deficits.

The study results have implications for clinical practice. As the care of premature babies continues to improve, neonatologists face new challenges to ensure that babies not only survive but thrive. They need to find ways to prevent against the lifelong impacts that preterm birth would otherwise have on the cerebellum and developing brain.

Read the full press release here.

Read the full journal article here.

structure of EGFR

Study suggests EGFR inhibition reverses alterations induced by hypoxia

structure of EGFR

The study suggests that specific molecular responses modulated by EGFR (seen here) may be targeted as a therapeutic strategy for HX injury in the neonatal brain.

Hypoxic (HX) encephalopathy is a major cause of death and neurodevelopmental disability in newborns. While it is known that decreased oxygen and energy failure in the brain lead to neuronal cell death, the cellular and molecular mechanisms of HX-induced neuronal and glial cell damage are still largely undefined.

Panagiotis Kratimenos, M.D., and colleagues from the Center for Neuroscience Research at the Children’s National Research Institute, discovered increased expression of activated-epidermal growth factor receptor (EGFR) in affected cortical areas of neonates with HX and decided to further investigate the functional role of EGFR-related signaling pathways in the cellular and molecular changes induced by HX in the cerebral cortex.

The researchers found that HX-induced activation of EGFR and Ca2+/calmodulin kinase IV (CaMKIV) caused cell death and pathological alterations in neurons and glia. EGFR blockade inhibited CaMKIV activation, attenuated neuronal loss, increased oligodendrocyte proliferation and reversed HX-induced astrogliosis.

The researchers also performed, for the first time, high-throughput transcriptomic analysis of the cortex to define molecular responses to HX and to uncover genes specifically involved in EGFR signaling in brain injury. Their results indicate that specific molecular responses modulated by EGFR may be targeted as a therapeutic strategy for HX injury in the neonatal brain.

This study defines many new exciting avenues of scientific exploration to further elucidate the beneficial impact of EGFR blockade on perinatal brain injury at the cellular and molecular levels. This analysis could potentially result in the identification of new therapeutic targets associated with EGFR signaling in the developing mammalian brain that are linked with specific long-term abnormalities caused by perinatal brain injury.

Children’s National researchers who contributed to this study include Panagiotis Kratimenos, M.D., Ioannis Koutroulis, M.D., Ph.D., M.B.A., Susan Knoblach, Ph.D., Payal Banerjee, Surajit Bhattacharya, Ph.D., Maria Almira-Suarez, M.D., and Vittorio Gallo, Ph.D.

Read the full article in iScience.