Findings link central congenital hypoventilation syndrome to the ubiquitin transfer system.
Researchers have identified a genetic mutation that may be responsible for a rare and deadly condition—central congenital hypoventilation syndrome (CCHS)—characterized by inadequate breathing during sleep, which, in its classic form, usually begins in newborns shortly after birth.
Treatment may include ventilators or respirators for constant or nighttime use or diaphragm implants for breathing control.
Gad Vatine, PhD, of Ben-Gurion University of the Negev and Avraham Ashkenazi, PhD, of Tel Aviv University are up-and-coming young principal investigators. Vatine is an expert in studying rare disorders using patient-specific stem cells, and Ashkenazi is an expert in tri-nucleotide repeat expansion disorders and protein clearance pathways.
While they don’t work on the same diseases, the Israeli Yad Laneshima patient organization thought they could work together to find treatments for CCHS. Sponsored initially by Yad Laneshima, and then by the international CCHS Network, Vatine and Ashkenazi began a collaboration that collaboration has yielded important new information about the cause of CCHS, which could lead to future treatments.
“Now that we know what goes wrong in the CCHS patient neurons, we can start developing modalities to fix it with the goal of promoting neuron survival that will allow better quality of life for the patients,” the researchers say in a release.
Their findings were published last month in the prestigious EMBO Journal.
CCHS is caused by a mutation in the PHOX2B gene, a key transcription factor in the development of the autonomic nervous system (ANS), a system that controls non-voluntary body functions such as breathing, digestion and heart rate. PHOX2B and eight other nuclear proteins that cause various neural disorders have a poly-alanine tract. In these disorders, a mutation that expands the poly-alanine tract causes the disease.
PhD students Fatima Amer-Sarsour from Ashkenazi’s lab and Daniel Falik from Vatine’s lab identified a poly-alanine that is also present in one of the enzymes of the ubiquitin transfer system. In a healthy condition, this poly-alanine stretch is required for enzyme recognition enabling proper ubiquitin transfer to target proteins, such as those involved in neural development, thereby controlling their degradation.
In a disease, such as in CCHS, the Vatine and Ashkenazi research teams discovered that the expansion mutation of the poly-alanine tract in PHOX2B (and in other poly-alanine disease-causing proteins) causes aberrant interaction with the poly-alanine recognizing enzyme of the ubiquitin transfer system. This interaction disrupts the proper ubiquitin transfer to neural proteins, which inhibits the ubiquitous normal functions, leading to cell death and eventually triggering CCHS.
To make this discovery clinically relevant, the Vatine lab at the Regenerative Medicine and Stem Cell Research Center at Ben-Gurion University used patient-specific stem cells, termed induced pluripotent stem cells. The center uses a technique called “reprogramming” that was developed by the Japanese Nobel Prize winner Shinya Yamanaka.
This technique enables easily accessible cells (like blood cells or skin cells) to be “taken back in time” to become identical to embryonic stem cells. Unlike embryonic stem cells, induced pluripotent stem cells are generated without destroying embryos, and can be generated from any individual. The induced pluripotent stem cells from CCHS patients were then differentiated into PHOX2B-expressing cells of the autonomic nervous system, which revealed the disease mechanism in the most vulnerable of the patient’s nerve cells.
“Using personalized, cutting-edge technologies, we have uncovered insights that can pave the way for significant advances in the disease therapeutics,” says Falik in a release.
Amer-Sarsour adds in a release, “I am thrilled with the progress we have made in identifying defective pathways in CCHS, as this opens up exciting research avenues to explore the development and function of the [autonomic nervous system].”