Dr. Sonntag received his MD degree in 1993 and his PhD degree in Virology in 1994 from University of Heidelberg, Germany. After an internship in Internal Medicine from 1993-1994, he worked as a Research Scientist in the Department of Virology at University of Heidelberg until 1995 when he became a Research Fellow in the Transplantation Biology Research Center at Massachusetts General Hospital, Boston. In 2000, he took a position as an Assistant Research Stem Cell Biologist in the Center for Neuroregeneration at McLean Hospital, Belmont, MA, and became an Instructor in Psychiatry at Harvard Medical School. In 2004 he was promoted to Associate Stem Cell Biologist and in 2005 to Assistant Professor in Psychiatry (Neuroscience). Dr. Sonntag is a molecular and cellular biologist and has extensive expertise in the fields of virology, immunology, and neurobiology. In his early career, Dr. Sonntag’s work has contributed to understanding the molecular evolution and biology of large DNA viruses, and to develop a gene therapy approach based on lentivirus vector technology and genetically modifying bone marrow stem cells to induce transplantation tolerance to organ grafts. His current scientific interest is to understand the molecular and cellular mechanisms and factors governing neuronal function and dysfunction in the aging brain and in neurodegenerative or neurological diseases. Dr. Sonntag’s research has contributed to developing novel technologies and systems, including pluripotent stem cell paradigms for neurogenesis, and lentivirus-mediated gene-engineering, as tools to study molecular mechanisms in neurodegeneration and neurological disorders, and as a source for cell therapy, such as the production of dopaminergic cell grafts to treating Parkinson’s disease (PD). Among others, his work has also contributed to understanding a role of dopamine D1 and adrenergic receptors in hedonic and impulsive behavior, dysregulated gene and miRNA expression networks in PD and schizophrenia, a novel mechanism to regulate neurotrophic growth factor-associated signaling pathways by miRNAs in context of PD and Alzheimer’s disease (AD)-associated toxic insult, and more recently, dysfunctional bioenergetics in the pathogenesis of late-onset AD (LOAD). Dr. Sonntag serves on several editorial boards and committees.