Professor Witt has been director of the Institute of Human Genetics of the Polish Academy of Sciences since 2016 and Head of the Department of Molecular and Clinical Genetics of the Institute for many years.
From 1998 to 2014 he was deputy Director for Scientific Affairs at the International Institute of Molecular and Cell Biology in Warsaw. Since 2019, he is a member of the scientific councils of the Institute of Bioorganic Chemistry PAS in Poznań and the Institute of Immunology and Experimental Therapy PAS in Wrocław.
In 1994 and 1996 visiting professor at NIH, Bethesda, USA. Afterwards, Prof. Witt has been involved in the introduction of moleular diagnostics standards of cystic fibrosis (CF) in Poland, what resulted in the creation at IHG PAS of an EU-certified, reference center for CF molecular diagnostics. Prof. Witt has also been a co-organizer of the Polish Working Group for Cystic Fibrosis, where since 1993 he has been a member of the Board of Directors. In parallel (1996-2002), prof. Witt has been a member of the Scientific/Medical Advisory Council (SMAC) of the International Cystic Fibrosis (Mucoviscidosis) Association (ICFMA). Recently, due to the interest in primary ciliary dyskinesia (PCD), Prof. Witt has been involved in the creation of the national reference center for PCD diagnostics (cooperation with the Institute of Tuberculosis and Lung Diseases, Rabka-Zdrój).
Since 2001, Prof. Witt has been an editor of the Human Genetics section of the Journal of Applied Genetics, board Member of the Postgraduate School of Molecular Medicine, of the Board of Directors of the Polish Genetics Society and the Polish Society of Human Genetics. Prof. Witt was also the initiator and the chairman of the panel of authors of drafts of two parliamentary bills: (i) on genetic testing, and (ii) on research on human material and biobanking.
Main scientific interests of Prof. Witt include molecular genetics of inherited diseases of respiratory tract (cystic fibrosis, immotile cilia syndrome); molecular aspects of hematooncologic diseases and of bone marrow transplantation. Since many years, as a specialist in clinical genetics, Prof. Witt has been involved in genetic counseling. He authored over 70 original papers, 34 reviews and 20 book chapters, published in: Hum Genet, Am J Reprod Immunol, Biochem Biophys Res Commun, J Immunol, Am J Med Genet, Ann Hum Genet, Clin Genet, J Med Genet, Pediatric Pulmonol, J Gerontol, Leukemia Res, Leukemia, etc.