# Sergiu P. Pașca

Sergiu P. Pașca (born January 30, 1982) is a Romanian-American scientist and physician at Stanford University in California. He is renowned for his groundbreaking work creating and developing stem cell-based models of the human brain to gain insights into neuropsychiatric disease. His lab was the first to develop and name assembloids: multi-unit self-organizing structures created in 3D cultures that allow for the study of human neural circuit and systems functions in vitro. Pașca’s lab generated and published human cortico-striatal and cortico-motor assembloids in 2020. Combining regionalized neural organoids pioneered in the lab and studies with human forebrain assembloids and transplantation, in 2024, Pașca developed a therapeutic for a severe genetic disorder called Timothy Syndrome, which was published on the cover of Nature.
Pașca is a pioneering neuroscientist and stem cell biologist and holds the Kenneth T. Norris Endowed Professorship in Psychiatry and Behavioral Sciences at Stanford University. He founded and leads the Stanford Brain Organogenesis Program as the Bonnie Uytengsu and Family Founding Director. He is part of the Stanford Neurosciences Institute, Stanford Bio-X and he is a fellow of the ChEM-H Institute at Stanford. Pașca was listed among New York Times Visionaries in Medicine and Sciences, he is the recipient of the 2018 Vilcek Award for Creative Biomedical Promise from the Vlicek Foundation, and the 2022 IBRO-Kemali Neuroscience Prize, and he holds a Doctor Honoris Causa. In 2022, he gave a TED talk on reverse engineering the human brain in the laboratory and in 2023 he became a Knight of the Order of Merit of Romania.

## Early life and education

Pașca was born in Cluj-Napoca, in the region of Transylvania. He was raised in nearby Aiud during the last years of communism. Pașca showed early on an interest in chemistry. He set up his first science lab at the age of 11, in the basement of his parents’ house. In the final year of high school, he won a prize in the national chemistry Olympiad, earning a scholarship to attend the university of his choice in Romania. In 2001, Pașca enrolled in the Iuliu Hațieganu University of Medicine and Pharmacy at Cluj-Napoca. As a medical student, he worked with Professor Maria Dronca to explore biochemical defects in autism spectrum disorders. At the same time, he studied electrophysiology at the Max Planck Institute for Brain Research in Frankfurt in Germany under Dr Danko Nikolic. After obtaining his M.D. in 2007, Pașca went to Stanford University in early 2009 as a postdoctoral fellow with Professor Ricardo Dolmetsch. At Stanford, he developed methods to derive neurons from induced pluripotent stem cells (iPSC) and used these neural cultures to identify cellular phenotypes associated with brain disorders, including Timothy syndrome and Dravet syndrome.
In 2014, he was recruited as a tenure-track Assistant Professor at Stanford University and opened his own laboratory. He became a tenured Associate Professor in 2020 and full Professor in 2022. He was soon after named an Endowed Professor at Stanford University.
In 2023, he received a Doctor Honoris Causa (D.H.C.) from Iuliu Hatieganu Medical School in Cluj-Napoca, Romania.
His personal trajectory was described in a Quanta profile by the American journalist Claudia Dreyfus.
Pașca has two children.

## Research

Pașca’s laboratory at Stanford University explores the biological mechanisms of neurodevelopmental disorders, such as autism spectrum disorders, epilepsy and schizophrenia, using cellular models of the human brain. Pașca developed some of the early in-a-dish models of disease by deriving neurons from skin cells taken from patients with genetic forms of autism and other neurodevelopmental disorders. These patient neurons helped uncover the cellular defects of genetic mutations and demonstrated the promise of this novel technology. In 2024, his lab reported a therapeutic developed exclusively with human stem cell-based models.
Neural organoids
In his laboratory, Pașca introduced the use of instructive signals to develop lab-grown self-assembling three-dimensional (3D) structures called regionalized neural spheroids or organoids. Through application of various guidance molecules, Pașca ’s lab has developed about a dozen distinct neural organoids representing different brain areas, including the cerebral cortex, ventral forebrain, striatum, spinal cord, thalamus and others. This method was listed among the Key Advances in hiPSC Disease Modeling of the Last Decade by the journal Cell Stem Cell, and Organoids were named Methods of the Year in 2017 by Nature Methods. These 3D brain tissue resemble specific regions of the nervous system and his laboratory has maintained these cultures for over 1000 days in vitro and demonstrated advanced cell maturation, including astrocytes, into postnatal stages according to an intrinsic clock. His work on astrocytes was inspired by the late Stanford neurobiologist Ben Barres.
Assembloids
Pașca has demonstrated that brain-region specific organoids can be fused to form brain assembloids, which spontaneously integrate and demonstrate emergent properties. He has employed this preparation to study the cross-talk between cells in the developing human brain and to mimic human brain circuits in a dish. Pașca coined the term assembloids in 2018 referring to the first forebrain assembloids developed in early 2017. This work was listed among the Top Research Advances of 2017 by the National Institutes of Health. His lab has subsequently developed cortico-striatal and three-part cortico-spinal-muscle assembloids. By combining assembloids with CRISPR screening, Pașca lab mapped hundreds of autism-related genes to interneuron development stages, which also revealed an unknown role of the endoplasmic reticulum in migration.
In 2024, his lab reported the first four-part assembloids that model the somatosensory pathway, enabling activity monitoring of the entire circuit and response to noxious stimuli. Assembloids are now widely used to model complex cell-cell interactions in other systems and organs, including the gut, immune system, cancer, etc.
Assembloids have been useful for studying neural migration, circuit formation, and unveiling a surprising ability of neural circuits to self-assemble, ex vivo, from parts.
Transplantation of organoids
In 2022, his group demonstrated the successful integration of human cortical organoids into the developing rat cerebral cortex. Human neurons displayed advanced maturation in vivo, responded to whisker stimulation and were capable of influencing the behavior of the rat in a reward task.
This work was extensively covered by the press. Pașca discussed the ethical implications of his work with the ethicist Insoo Hyun in a video material filmed at the Boston Science Museum. Pașca acknowledged that organoid transplantation offers great promise for characterizing human cellular processes in vivo but encourages caution and ethical consideration in pursuing these experiments.
Stanford Brain Organogenesis
In 2019, Pașca founded the Stanford Brain Organogenesis Program, which is a university wide effort to leverage technologies developed at Stanford to advance our understanding of human brain development and circuit assembly. The program includes Karl Deisseroth, Zhenan Bao, Bianxiao Cui, Michael Lin, Sarah Heilshorn and Hank Greely . Pașca serves as the Bonnie Uytengsu and Family Director. The program is also broadly sharing organoid and assembloids technologies through a free, hands-on course course that brings student from all over the world.
Teaching and public engagement
At Stanford, Pașca teaches neural development and principles of drug discovery in neuroscience. Pașca is also the co-director of the CSHL Workshop on autism spectrum disorders.
In 2022, he gave a TED talk at the Vancouver event describing the potential of human cellular models to understand disease.

## Honors

Pașca is a Chan Zuckerberg Initiative Ben Barres Investigator and a CZ BioHub Investigator. He was a New York Stem Cell Foundation Roberston Stem Cell Investigator. His researched activity gained him several awards:
* Schaller Prize for Translational Neuroscience (2024)
* ISSCR Momentum Award, International Society for Stem Cell Research (2024)
* Knight of the Order of Merit, The Chancery of Orders (2023)
* Sumitomo/Sunovion Prize, International College of Neuropsychopharmacology (2023)
* Doctor Honoris Causa (D.H.C.), Hatieganu Medical School (2023)
* IBRO Dargut and Milena Kemali International Prize for Basic and Clinical Neurosciences (2022)
* Judson Daland Prize for Outstanding Achievement in Clinical Investigation, American Society of Philosophy (2021)
* Joseph Altman Award in Developmental Neuroscience (2021)
* Schizophrenia Basic Research Award (2021)
* C.J. Herrick Award in Neuroanatomy (2020)
* A.E.Bennett Award, Society of Biological Psychiatry (2018)
* Daniel H. Efron Award, American College of Neuropsychopharmacology (2018)
* Günter Blobel Award, American Society of Cell Biology (2018)
* New York Times Visionaries in Science and Medicine (2018)
* Vilcek Award for Creative Biomedical Promise (2018)
* Jordi Folch-Pi Award, American Society for Neurochemistry (2017)
* NARSAD Independent Investigator Award (2017)
* NIMH Director's BRAINS Award (2015)
* MQ Fellow Award for Transforming Mental Health (2014)
* Sammy Kuo Award (2012)
* IBRO Outstanding Research Fellow (2009)
In Romania, he was recognized as the Best Romanian student studying abroad in 2012.