A study by the University of California, San Diego (UCSD) uses laboratory-grown human brain tissue to detect nerve abnormalities in Pete-Hopkins syndrome and test gene therapy.
In a study published May 2, 2022 in the Journal The nature of communication, scientists from the University of California, San Diego School of Medicine used human brain organelles to discover how a genetic mutation associated with severe autism impairs the development of the nervous system. The use of gene therapy tools to restore gene function has successfully saved nerve structure and function.
Several neurological and neuropsychiatric disorders, including autism spectrum disorder (ASD) and schizophrenia, have been associated with mutations in transcription factor 4.TCF4), a necessary 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 is mutated.
To study this question, the researchers focused on Pete-Hopkins syndrome, a RAS specifically caused by mutations in TCF4. Children with a genetic disease have profound cognitive and motor impairments and are usually nonverbal.
Pete-Hopkins syndrome (PTGS) is a rare genetic disease characterized by developmental delay, epilepsy, personality traits, and possible recurrent hyperventilation followed by apnea. As more about Pete-Hopkins became known, the spectrum of developmental disorders is expanding to cover difficulties with autism, anxiety, ADHD, and sensory disorders. This is due to an abnormality in chromosome 18, in particular the inadequate expression of the TCF4 gene.
Existing mouse models of Pitt-Hopkins syndrome cannot accurately mimic patients ’neural characteristics, so the UCSD team instead created a model to study the disease in humans. Using stem cell technology, they transformed patients ’skin cells into stem cells, which were then developed into three-dimensional brain organelles or“ mini-brains ”.
Initial observations of brain organelles revealed many structural and functional differences between TCF4-mutated samples and their control.
“Even without a microscope, one could tell which brain organoid had a mutation,” said senior study author Alisson R. Muotry, Ph.D., a professor at UC San Diego School of Medicine, director of the UC San Diego stem cell program and a member of the Sanford Regener Consortium medicine.
The TCF4-mutated organelles were significantly smaller than normal organelles, and many of the cells were not neurons but neuronal progenitors. These simple cells are designed to multiply and then mature into specialized brain cells, but in mutated organelles part of this process has gone wrong.
A series of experiments showed that TCF4 the mutation resulted in downstream regulation SOX Wnt genes and pathways are two important molecular signals that guide embryonic cells to proliferate, mature into neurons and migrate to the right place in the brain.
Because of this dysregulation, nerve progenitors did not reproduce efficiently, and thus fewer cortical neurons were formed. Cells that matured into neurons were less excitable than usual and often remained grouped together instead of organizing themselves into fine-tuned neural circuits.
This atypical cellular architecture disrupted the flow of neural activity in the mutated organelle of the brain, which, according to the authors, is likely to contribute to impaired cognitive and motor functions in the future.
“We were surprised to see such serious development problems on all these different scales, and it made us think about what we can do to solve them,” said first author Fabio Papes, Ph.D., associate professor at Campinas University and visiting scientist. with UC. San Diego Medical School, which along with Muotri managed the work. Papes has a relative with Pete-Hopkins syndrome who motivated him to study TCF4.
The team tested two different gene therapy strategies to restore a functional gene in brain tissue. Both methods are effectively increasing TCF4 levels, and at the same time corrected the phenotypes of Pete-Hopkins syndrome at the molecular, cellular and electrophysiological scales.
“The fact that we can fix this one gene and the whole nervous system is recovering, even at the functional level, is amazing,” Muotri said.
Muotry notes that these genetic interventions occurred in the prenatal stage of brain development, whereas in a clinical setting children will receive diagnosis and treatment in a few years. Therefore, clinical trials must first confirm whether the next intervention is still safe and effective. The team is currently optimizing its newly licensed gene therapy tools in preparation for a trial in which spinal injections of a genetic vector hopefully restore TCF4 function in the brain.
“For these children and their loved ones, any improvement in motor and cognitive functions and quality of life should be tried,” said Muotri.
“What’s really remarkable about this work is that these researchers are going beyond the lab and working hard to get those findings translated into the clinic,” said Audrey Davidov, president of the Pete Hopkins Research Foundation. “It’s much more than stellar academic work; it is a real measure of what well-practiced science can achieve to hopefully change people’s lives for the better. ”
Reference: “Loss of transcription factor 4 function due to deficiency of progenitor proliferation and content of cortical neurons” Fabio Papeza, Antonio P. Camargo, Janaina S. de Souza, Vinicius MA Carvalho, Ryan A. Seto, Erin La Montagne, Jose R Teixeira, Simony H. Avansini, Sandra M. Sanchez-Sanchez, Thiago S. Nakahara, Carolina N. Santa, Wei Wu, Hang Yao, Barbara MP Araujo, Paul Enf Velho, Gabriel G. Haddad and Allison R. Muotry May 2, 2022, The nature of communication.
DOI: 10.1038 / s41467-022-29942-w
Co-authors include: Janaina de Souza, Ryan A. Seto, Erin Lamantan, Simoni H. Avansini, Sandra M. Sanchez-Sanchez, Wei Wu, Hang Yao and Gabriel Hadad of UC San Diego; Antonio P. Camargo, Vinicius MA Carvalho, Jose R. Teixeira, Thiago S. Nacajar, Carolina N. Santa, Barbara MP Araujo and Paul E. F. Velho at the Campinas University.
This work was funded, in part, by the National Institutes of Health (grant R01 MH123828), the Pete Hopkins Research Foundation, the Sao Paulo Research Foundation (grants 2020 / 11451-7, 2018 / 03613-7, 2018 / 04240-0) and the United Genome Institute of the U.S. Department of Energy (DE-AC02-05CH11231).
Disclosure: Alison R. Muotry is a co-founder and has a stake in TISMOO, a company that specializes in the genetic analysis and organogenesis of the human brain.