The University of California, San Diego (UCSD) study uses laboratory-grown human brain tissue to detect neuronal abnormalities in Pitt-Hopkins syndrome and test gene therapy tools.
In a study published in the journal May 2, 2022 Nature CommunicationsResearchers at the University of California, San Diego School of Medicine have used organelles in the human brain to determine how a genetic mutation disrupts nerve development due to severe forms of autism. The use of gene therapy tools to restore gene function has successfully maintained neural structure and function.
Several neurological and neuropsychiatric disorders, including autism spectrum disorder (ASD) and schizophrenia, have been associated with 4 transcription factor mutations (TCF4), an important gene in brain development. Transcription factors regulate when other genes are turned on or off, so their presence or absence may have a domino effect in the developing embryo. However, little is known about what happens to the human brain TCF4 mutated.
To study this question, the researchers focused on Pitt-Hopkins syndrome, especially ASD caused by mutations. TCF4. Children with a genetic condition have profound cognitive and behavioral disorders and are usually non-verbal.
Pitt-Hopkins syndrome (PTHS) is a rare genetic disorder characterized by developmental delay, epilepsy, facial features, and intermittent hyperventilation that may be accompanied by apnea. As more is learned about Pitt-Hopkins, the spectrum of disease progression includes complications associated with autism, anxiety, ADHD, and sensory disorders. This abnormality inside chromosome 18 is associated with, in particular, adequate expression of the TCF4 gene.
Current mouse models of Pitt-Hopkins syndrome cannot accurately mimic patients’ neural characteristics, so the UCSD team developed a human study model of the disease instead. Using single-cell technology, they transformed patients’ skin cells into stem cells, which were then transformed into three-dimensional brain organelles, or “mini-brains.”
Early observations of brain organelles revealed structural and functional differences between brain organelles. TCF4-mutated samples and their management.
“Even under a microscope, you could tell which organelle in the brain has a mutation,” said senior researcher Alison R. Muotri, PhD, Professor, UC San Diego School of Medicine, Director and Member of the UC San Diego Stem Cell Program. Sanford Consortium for Regenerative Medicine.
The TCF4-mutated organelles were much smaller than normal organelles, and most of the cells were in fact neuronal progenitors, not neurons. These simple cells are designed to multiply and then reach specialized brain cells, but in mutated organelles, part of this process has gone wrong.
A number of experiments revealed TCF4 The mutation led to downstream disregulation SOX The genes and the Wnt pathway are two important molecular signals that allow embryonic cells to multiply, mature into neurons, and migrate to the right place in the brain.
Due to this disregulation, neuronal progenitors did not increase effectively and thus fewer cortical neurons were produced. Cells that became neurons were less irritating than usual and often clustered together instead of placing themselves in carefully tuned neural circuits.
This atypical cellular architecture disrupted the flow of neural activity in the mutated brain organelle, which, according to the authors, contributes to cognitive and motor dysfunction.
“We were amazed to see these major development challenges at different scales and this left us wondering what we could do to address them,” said Fabio Papes, the first author, PhD, an associate professor at Campinas University and a scientist at UC. San Diego Medical School, in partnership with Muotri. Papes has a relative with Pitt-Hopkins syndrome who was motivated to study. TCF4.
The team tested two different gene therapy strategies to restore a functional gene in the brain tissue. Both methods have increased efficiency TCF4 level, and thereby, corrected the phenotypes of Pitt-Hopkins syndrome on a molecular, cellular, and electrophysiological scale.
“It’s amazing that we can fix one gene and the whole nervous system will regenerate itself, even on a functional level,” Muotri said.
Muotri noted that these genetic interventions took place in the prenatal stage of brain development, and in the clinical setting, children receive diagnosis and treatment after a few years. Thus, clinical trials should first confirm that later intervention is still safe and effective. The team is currently optimizing recently licensed gene therapy tools to prepare for such a test where genetic vector spinal injections can restore TCF4 function in the brain.
“It is worth the effort to improve motor-cognitive function and quality of life for children and their loved ones,” Muotri said.
Audrey Davidov, president of the Pitt Hopkins Research Foundation, said: “The great thing about this is that these researchers are working hard to go beyond the lab and transfer these findings to the clinic.” “It’s a lot more than a stellar academic paper; It’s a real testament to what well-practiced science can do to change people’s lives for the better. ”
Reference: “Loss of function of transcription factor 4 is associated with a lack of progenitor proliferation and cortical neuron content” Fabio Papes, Antonio P. Kamargo, Zhanaina S. de Souza, Vinicius M.A. Carvalho, Ryan A. Seto, Erin Lamontan, Jose R. Teixeira, Simoni H. Avansini, Sandra M. Sanchez-Sanchez, Thiago S. Nakahara, Carolina N. Santo, Wei Wu, Hang Yao, Barbara MP Arauho, Paulo ENF Velho, Gabriel G. Haddad and Alisson R. Muatri, May 2, 2022, Nature Communications.
DOI: 10.1038 / s41467-022-29942-w
Co-authors include: Janaina S. de Souza, Ryan A. Szeto, Erin LaMontagne, Simoni H. Avansini, Sandra M. Sanchez-Sanchez, Wei Wu, Hang Yao and Gabriel Haddad at UC San Diego; Antonio P. Camargo, Vinicius MA Carvalho, Jose R. Teixeira, Thiago S. Nakahara, Carolina N. Santo, Barbara MP Araujo and Paulo ENF Velho at Campinas University.
This work was partially funded by the National Institutes of Health (grant R01 MH123828), the Pitt Hopkins Research Foundation, and the São Paulo Research Foundation (grants 2020 / 11451-7, 2018 / 03613-7, 2018 / 04240-0). ) and the Joint Genome Institute of the U.S. Department of Energy (DE-AC02-05CH11231).
Disclosure: Alison R. Muotri is a co-founder and co-founder of TISMOO, a company dedicated to genetic analysis and organogenesis of the human brain.