Scientists at the University of North Carolina School of Medicine have shown for the first time that postpartum gene therapy may be able to prevent or reverse many of the harmful effects of a rare genetic disorder called Pitt-Hopkins syndrome. This autism spectrum disorder has severe developmental delay, intellectual disability, breathing and movement abnormalities, anxiety, seizures and mild but distinctive facial abnormalities.
The scientists report their findings in the journal Elef, designed an experimental gene therapy-like technique to restore normal activity in genetically defective patients with Pitt-Hopkins syndrome. In newborn mice that otherwise mimicked the syndrome, the treatment prevented signs of the disease, including anxiety-like behaviors, memory problems and abnormal gene expression patterns in affected brain cells.
“The first proof-of-principle shows that restoring normal levels of the Pitt-Hopkins syndrome gene is a viable therapy for Pitt-Hopkins syndrome, for which there is otherwise no specific treatment,” said senior author Ben Philpot, Ph.D., Kenan Distinguished University of North Carolina Medicine Professor of Cell Biology and Physiology and Associate Director of the Center for Neuroscience at the University of North Carolina.
Most genes are inherited in pairs, one from the mother and one from the father. Pitt-Hopkins syndrome occurs in a child when one gene copy TCF4 Deletion or mutation, resulting in insufficient levels of TCF4 protein. Typically, such deletions or mutations occur spontaneously in the parental egg or sperm cell, either before conception or in the earliest stages of embryonic life after conception.
Since the syndrome was first described by Australian researchers in 1978, only about 500 cases of the syndrome have been reported worldwide. But no one knows the true prevalence of the syndrome. Some estimates suggest there could be more than 10,000 cases in the United States alone.
since TCF4 is a “transcription factor” gene, a master switch that controls the activity of at least hundreds of other genes, and its disruption from the onset of development can lead to many developmental abnormalities.In principle, these abnormalities are prevented by returning to normal TCF4 Early expression is the best therapeutic strategy — but it has not been tested.
Philpot’s team, led by first author Hyojin (Sally) Kim, Ph.D., a graduate student in Philpot’s lab, developed a mouse model of Pitt-Hopkins syndrome in which the mouse version of TCF4 levels can be reliably halved. The mouse model showed many typical signs of disease. Restoring the full activity of the gene from the start of embryonic life completely prevents these signs. The researchers also found evidence in these preliminary experiments that basically all types of neurons need to restore gene activity to prevent Pitt-Hopkins signs.
The researchers next set up a proof-of-concept experiment that simulates a real-world gene therapy strategy.In engineered mice, about half of which expressed the mouse version Tcf4 After being turned off, the researchers used a virus-delivered enzyme to turn the missing expression back on again in neurons after the mice were born. Analysis of the brain showed that this activity returned over the next few weeks.
Although the treated mice had slightly smaller brains and bodies than normal mice, they did not develop many of the abnormal behaviors seen in the untreated Pitt-Hopkins model mice. One exception was innate nesting behavior, in which treated mice appeared abnormal at first, although their abilities returned to normal within a few weeks.
The treatment at least partially reversed two other abnormalities observed in untreated mice: changes in the levels of genes regulated by TCF4 and changes in neuronal activity patterns measured in electroencephalogram (EEG) recordings.
“These findings offer hope that future gene therapy will bring significant benefits to individuals with Pitt-Hopkins syndrome, even during postpartum delivery; it does not require diagnosis and treatment in the wombsaid Kim.
Philpot and his lab now plan to explore the effectiveness of their strategy later in life when applied to Pitt-Hopkins mice.They also plan to develop an experimental gene therapy in which humans TCF4 The gene itself will be delivered virally into a Pitt-Hopkins mouse model — a therapy that could eventually be tested in children with Pitt-Hopkins syndrome.
“We will be working on gene therapy, but our findings suggest that there are other potentially effective approaches to TCF4 restoration, including treatments that boost remaining TCF4 activity, good TCF4 Copy,” Philpot said.
The research was supported by the Pitt Hopkins Research Foundation, the National Institute of Neurological Disorders and Stroke (R01NS114086), the Estonian Research Council, and the Ann D. Bornstein Grant of the Center for Orphan Diseases at the Perelman School of Medicine in Pennsylvania (MDBR- 21-105-Pitt Hopkins).