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Katarzyna Klonowska, PhD




Research Fellow




Research Fellow




Katarzyna Klonowska, Joannes M. Grevelink, Krinio Giannikou, Eleonora Aronica, Barbara A. Ogorek, Zachary T. Herbert, Aaron R. Thorner, Thomas N. Darling, Joel Moss, and David J. Kwiatkowski

Analysis of second-hit events in Tuberous Sclerosis Complex normal tissues and lesions

As a researcher focused on unravelling genetic variation underlying human diseases, I believe that major scientific achievements in clinical genetics are possible thanks to close collaboration of researchers and clinicians, enabling to complement our expertise. Women in Medicine and Science Symposium provides a unique opportunity to appreciate our commitment to scientific work, highlight outstanding accomplishments of women in Brigham and Women’s Hospital and eventually empower all women committed to research. WMSS provides a chance to learn about the ongoing research initiatives and establish new exciting collaborations in our diverse BWH community.


Tuberous sclerosis complex (TSC) is due to inactivating TSC1/TSC2 mutationsleading to tumors, including facial angiofibroma (FAF) and cortical tubers, known to develop through two-hit mechanism. Here we explored frequency of second-hit mutation events.


We developed a Multiplex High-sensitivity PCR Assay (MHPA), enabling mutation detection at extremely low (<0.1%) variant allele frequencies (VAF).


TSC2-MHPA analysis of 81 samples, including 24 FAFs from TSC2 mosaic patients,revealed that UV-induced second-hit causing TSC2 inactivation was pervasive in TSC facial skin, with an average of 4.8 mutations per 2-mm FAF at median VAF=0.08%, generating >150,000 facial tumors (subclinical ‘micro-FAFs’) in the average TSC subject (Klonowska et al.,JCI,2022). TSC1-MHPA analysis of 6 FAFs from TSC1 mosaic patients showed that UV-mutations are less common in TSC1 (average 0.8 mutations) than in TSC2 (p=0.006). TSC2-MHPA of tubers identified nonsynonymous somatic SNV/indels in 6 of 13 (46%) tubers (median VAF=0.06%).


Our TSC2-MHPA analysis of FAF revealed that TSC facial skin can be viewed as harboring a patchwork of clonal fibroblast proliferations (micro-FAFs), a small proportion of which develop into clinically observable FAF. Such lesions are much less common in TSC1 than in TSC2. TSC2-MHPA of TSC tubers identified TSC2 second-hits in some lesions.