Parvalbumin (PV) interneurons act as the brain’s rhythm keepers. By regulating local circuit activity and maintaining excitation–inhibition balance, they help stabilize cortical network function. When these cells malfunction or decline—as seen in disorders such as schizophrenia and epilepsy—neural networks can become unstable, leading to cognitive and behavioral disruptions. Yet despite their importance, PV interneurons have been difficult to generate in vitro, with multiple studies noting the challenge of producing subtype‑specific PV cells from stem cell or fetal sources.
A team at Lund University now reports a major step toward overcoming that barrier. In a study published in Science Advances titled “A distinct lineage pathway drives parvalbumin chandelier cell fate in human interneuron reprogramming,” the researchers describe a method to directly reprogram human glial cells into PV interneurons without passing through a stem‑cell stage. The approach builds on their earlier work but adds a deeper understanding of the lineage transitions that drive PV identity.
“In our study, we have for the first time succeeded in reprogramming human glial cells into parvalbumin neurons that resemble those that naturally exist in the brain,” said Daniella Rylander Ottosson, PhD, senior author and researcher in regenerative neurophysiology at Lund University. “We have also been able to identify several key genes that seem to play a crucial role in the transformation.”
The team used human stem‑cell–derived glial progenitor cells (hGPCs) and introduced a defined set of five transcription factors—Ascl1, DLX5, LHX6, Sox2, and FOXG1—to drive interneuron reprogramming. Within weeks—far faster than traditional stem‑cell differentiation protocols—the glial cells adopted neuronal morphology, expressed GABAergic markers, and developed electrophysiological properties consistent with inhibitory interneurons.
Single‑nucleus RNA sequencing revealed that the reprogrammed cells rapidly transitioned through distinct developmental states, ultimately forming several neuronal clusters. Among them was a robust PV‑enriched population with molecular signatures characteristic of chandelier cells. The analysis also uncovered a previously uncharacterized lineage trajectory leading to PV fate, including dynamic gene programs that appear essential for establishing the chandelier‑cell phenotype.
The work addresses a long‑standing challenge in the field: generating subtype‑specific PV interneurons efficiently and reliably. Because glial cells are abundant, proliferative, and widely distributed throughout the brain, direct reprogramming offers a potential route to repair inhibitory circuits affected in neurological and psychiatric disorders. However, transferring glia reprogramming to the human system has been difficult, in part because hGPCs develop relatively late, the authors noted. The researchers overcame this hurdle by using a stem‑cell–derived hGPC protocol that produces oligodendrocyte precursor–like cells, which they and others have previously shown can be successfully converted into interneurons.
The discovery of a PV‑specific lineage pathway also highlights previously unknown PV‑fate genes that could inform future refinements to reprogramming strategies. As for the future of brain cell engineering, the ability to generate mature human PV interneurons quickly and reproducibly may become a cornerstone of future circuit‑repair therapies.
