Honors & Awards

  • Fellow Award, Leukemia and Lymphoma Society (July 2016 - July 2020)

Professional Education

  • Doctor of Philosophy, University of Cambridge (2015)
  • Master of Arts (Cantab), University of Cambridge (2014)
  • Bachelor of Arts, University of Cambridge (2010)

Stanford Advisors

Current Research and Scholarly Interests

Investigating the role of R-loops in genome instability and cancer.

All Publications

  • qDRIP: a method to quantitatively assess RNA-DNA hybrid formation genome-wide. Nucleic acids research Crossley, M. P., Bocek, M. J., Hamperl, S. n., Swigut, T. n., Cimprich, K. A. 2020


    R-loops are dynamic, co-transcriptional nucleic acid structures that facilitate physiological processes but can also cause DNA damage in certain contexts. Perturbations of transcription or R-loop resolution are expected to change their genomic distribution. Next-generation sequencing approaches to map RNA-DNA hybrids, a component of R-loops, have so far not allowed quantitative comparisons between such conditions. Here, we describe quantitative differential DNA-RNA immunoprecipitation (qDRIP), a method combining synthetic RNA-DNA-hybrid internal standards with high-resolution, strand-specific sequencing. We show that qDRIP avoids biases inherent to read-count normalization by accurately profiling signal in regions unaffected by transcription inhibition in human cells, and by facilitating accurate differential peak calling between conditions. We also use these quantitative comparisons to make the first estimates of the absolute count of RNA-DNA hybrids per cell and their half-lives genome-wide. Finally, we identify a subset of RNA-DNA hybrids with high GC skew which are partially resistant to RNase H. Overall, qDRIP allows for accurate normalization in conditions where R-loops are perturbed and for quantitative measurements that provide previously unattainable biological insights.

    View details for DOI 10.1093/nar/gkaa500

    View details for PubMedID 32544226

  • R-Loops as Cellular Regulators and Genomic Threats. Molecular cell Crossley, M. P., Bocek, M., Cimprich, K. A. 2019; 73 (3): 398–411


    During transcription, the nascent RNA strand can base pair with its template DNA, displacing the non-template strand as ssDNA and forming a structure called an R-loop. R-loops are common across many domains of life and cause DNA damage in certain contexts. In this review, we summarize recent results implicating R-loops as important regulators of cellular processes such as transcription termination, gene regulation, and DNA repair. We also highlight recent work suggesting that R-loops can be problematic to cells as blocks to efficient transcription and replication that trigger the DNA damage response. Finally, we discuss how R-loops may contribute to cancer, neurodegeneration, and inflammatory diseases and compare the available next-generation sequencing-based approaches to map R-loops genome wide.

    View details for PubMedID 30735654

  • Faulty replication can sting NATURE Crossley, M. P., Cimprich, K. A. 2018; 557 (7703): 34–35

    View details for Web of Science ID 000431234500021

    View details for PubMedID 29713064

  • Targeting Functional Noncoding RNAs. Methods in molecular biology (Clifton, N.J.) Crossley, M. P., Krude, T. 2017; 1565: 151-160


    Noncoding RNAs have essential biochemical functions in different areas of cellular metabolism, including protein synthesis, RNA splicing, protein secretion, and DNA replication. We have successfully used Morpholino antisense oligonucleotides for the functional inactivation of small noncoding RNAs required for DNA replication (Y RNAs in vertebrates and stem-bulge RNAs in nematodes). Here we discuss specific issues of targeting functional noncoding RNAs for inactivation by Morpholino antisense oligonucleotides. We present protocols for the design, preparation, and efficacy controls of Morpholino antisense oligonucleotides, as well as brief descriptions for their delivery into vertebrate and nematode embryos.

    View details for DOI 10.1007/978-1-4939-6817-6_13

    View details for PubMedID 28364241

  • Structural and functional analysis of four non-coding Y RNAs from Chinese hamster cells: identification, molecular dynamics simulations and DNA replication initiation assays BMC Molecular Biology Neto, Q. A., Junior, F. F., Bueno, P. S., Seixas, F. A., Kowalski, M. P., Kheir, E., Krude, T., Fernandez, M. A. 2016
  • Co-transcriptional R-loops are the main cause of estrogen-induced DNA damage eLIFE Stork, C. T., Bocek, M., Crossley, M. P., Sollier, J., Sanz, L. A., Chédin, F., Swigut, T., Cimprich, K. A. 2016


    The hormone estrogen (E2) binds the estrogen receptor to promote transcription of E2-responsive genes in the breast and other tissues. E2 also has links to genomic instability, and elevated E2 levels are tied to breast cancer. Here, we show that E2 stimulation causes a rapid, global increase in the formation of R-loops, co-transcriptional RNA-DNA products, which in some instances have been linked to DNA damage. We show that E2-dependent R-loop formation and breast cancer rearrangements are highly enriched at E2-responsive genomic loci and that E2 induces DNA replication-dependent double-strand breaks (DSBs). Strikingly, many DSBs that accumulate in response to E2 are R-loop dependent. Thus, R-loops resulting from the E2 transcriptional response are a significant source of DNA damage. This work reveals a novel mechanism by which E2 stimulation leads to genomic instability and highlights how transcriptional programs play an important role in shaping the genomic landscape of DNA damage susceptibility.

    View details for DOI 10.7554/eLife.17548

    View details for PubMedCentralID PMC5030092

  • Non-coding stem-bulge RNAs are required for cell proliferation and embryonic development in C-elegans JOURNAL OF CELL SCIENCE Kowalski, M. P., Baylis, H. A., Krude, T. 2015; 128 (11): 2118-2129


    Stem bulge RNAs (sbRNAs) are a family of small non-coding, stem-loop RNAs present in C. elegans and other nematodes, the function of which is unknown. Here, we report the first functional characterisation of nematode sbRNAs. We demonstrate that sbRNAs from a range of nematode species are able to reconstitute the initiation of chromosomal DNA replication in the presence of replication proteins in vitro, and that conserved nucleotide sequence motifs are essential for this function. By functionally inactivating sbRNAs with antisense morpholino oligonucleotides we show that sbRNAs are required for S phase progression, early embryonic development and viability of C. elegans in vivo. Thus, we demonstrate a novel and essential role for sbRNAs during the early development of C. elegans. sbRNAs show limited nucleotide sequence homology to vertebrate Y RNAs, which are also essential for the initiation of DNA replication. Our results therefore establish that the essential function of small non-coding stem-loop RNAs during DNA replication extends beyond vertebrates.

    View details for DOI 10.1242/jcs.166744

    View details for Web of Science ID 000355559600011

    View details for PubMedID 25908866

  • Functional roles of non-coding Y RNAs. The international journal of biochemistry & cell biology Kowalski, M. P., Krude, T. n. 2015


    Non-coding RNAs are involved in a multitude of cellular processes but the biochemical function of many small non-coding RNAs remains unclear. The family of small non-coding Y RNAs is conserved in vertebrates and related RNAs are present in some prokaryotic species. Y RNAs are also homologous to the newly identified family of non-coding stem-bulge RNAs (sbRNAs) in nematodes, for which potential physiological functions are only now emerging. Y RNAs are essential for the initiation of chromosomal DNA replication in vertebrates and, when bound to the Ro60 protein, they are involved in RNA stability and cellular responses to stress in several eukaryotic and prokaryotic species. Additionally, short fragments of Y RNAs have recently been identified as abundant components in the blood and tissues of humans and other mammals, with potential diagnostic value. While the number of functional roles of Y RNAs is growing, it is becoming increasingly clear that the conserved structural domains of Y RNAs are essential for distinct cellular functions. Here, we review the biochemical functions associated with these structural RNA domains, as well as the functional conservation of Y RNAs in different species. The existing biochemical and structural evidence supports a domain model for these small non-coding RNAs that has direct implications for modular evolution of functional non-coding RNAs.

    View details for PubMedID 26159929

  • Nucleotide contributions to the structural integrity and DNA replication initiation activity of noncoding y RNA BIOCHEMISTRY Wang*, I., Kowalski*, M. P., Langley, A. R., Rodriguez, R., Balasubramanian, S., Hsu, S. T., Krude, T. 2014; 53 (37): 5848-5863

    View details for DOI 10.1021/bi500470b

  • CXCL12/CXCR4 Blockade Induces Multimodal Antitumor Effects That Prolong Survival in an Immunocompetent Mouse Model of Ovarian Cancer CANCER RESEARCH Righi, E., Kashiwagi, S., Yuan, J., Santosuosso, M., LeBlanc, P., Ingraham, R., Forbes, B., Edelblute, B., Collette, B., Xing, D., Kowalski, M., Mingari, M. C., Vianello, F., Birrer, M., Orsulic, S., Dranoff, G., Poznansky, M. C. 2011; 71 (16): 5522-5534


    The chemokine CXCL12 and its receptor CXCR4 are expressed widely in human cancers, including ovarian cancer, in which they are associated with disease progression at the levels of tumor cell proliferation, invasion, and angiogenesis. Here, we used an immunocompetent mouse model of intraperitoneal papillary epithelial ovarian cancer to show that modulation of the CXCL12/CXCR4 axis in ovarian cancer has multimodal effects on tumor pathogenesis associated with induction of antitumor immunity. siRNA-mediated knockdown of CXCL12 in BR5-1 cells that constitutively express CXCL12 and CXCR4 reduced cell proliferation in vitro, and tumor growth in vivo. Similarly, treatment of BR5-1-derived tumors with AMD3100, a selective CXCR4 antagonist, resulted in increased tumor apoptosis and necrosis, reduction in intraperitoneal dissemination, and selective reduction of intratumoral FoxP3(+) regulatory T cells (Treg). Compared with controls, CXCR4 blockade greatly increased T-cell-mediated antitumor immune responses, conferring a significant survival advantage to AMD3100-treated mice. In addition, the selective effect of CXCR4 antagonism on intratumoral Tregs was associated with both higher CXCR4 expression and increased chemotactic responses to CXCL12, a finding that was also confirmed in a melanoma model. Together, our findings reinforce the concept of a critical role for the CXCL12/CXCR4 axis in ovarian cancer pathogenesis, and they offer a definitive preclinical validation of CXCR4 as a therapeutic target in this disease.

    View details for DOI 10.1158/0008-5472.CAN-10-3143

    View details for Web of Science ID 000293831500018

    View details for PubMedID 21742774