Juel Rasmussen Group
To understanding the genetic origins of complex diseases, as well as the impact of environmental factors, is the central challenge of modern biomedicine.
DNA mismatch repair - HNPCC:
It is known that defects in DNA mismatch repair (MMR) activity result in increased spontaneous mutation rates and the first example linking colon cancer to a mutator defect was the discovery of MMR defects in Hereditary Nonpolyposis Colorectal Cancer (HNPCC) patients. At present, germline mutations of several genes, orthologs of bacterial components involved in MMR, have been found in HNPCC patients, i.e., hEXO1, hMSH2, hMSH6, hMLH1, hPMS1 and hPMS2. The early onset of colorectal cancer and a broad spectrum of extracolonic cancers characterize HNPCC. HNPCC gene carriers inherit a mutation in one of the alleles encoding a MMR gene, and the second copy is mutated or lost as an early event in the development of a tumor. This second event renders cells MMR deficient, presumably leading to the rapid accumulation of mutations that drive tumor development. What exactly causes the underlying predisposition to colorectal cancer in HNPCC individuals remains to be elucidated. However, emerging data suggest that depending on the nature of mutation in the MMR genes and the expression both the composition and the activity of the DNA repair complexes may vary among HNPCC individuals.
DNA mismatches can arise through DNA replication errors, physical damage, or heteroduplex formation during genetic recombination. If left unrepaired, these mismatches become fixed in the genome as mutations. Models for the initiation of MMR have been developed based on structural, genetic as well as biochemical studies. In these models, a mismatch is first recognized and bound by either the hMSH2-hMSH6 or the hMSH2-hMSH3 complex. The hMLH1-PMS2 complex is believed to create a contact between an endonuclease (MutH homolog) and the hMSH2-hMSH6/hMSH2-hMSH3 complexes. The endonuclease activity is thereby activated and a single nick is introduced into the newly synthesized strand. The DNA double helix is unwound by helicases and exonucleases remove the bases on the newly synthesized strand. DNA polymerase fills in the excision tract and DNA ligase closes the nick.
- To identify new nuclear and mitochondrial MMR proteins and to characterize their biological roles
- To develop biochemical assays to diagnose HNPCC and other cancers with defective MMR
- Identify molecular targets for development of strategies for treatment of HNPCC and related cancers
Genomic instability and mitochondrial function - mitochondrial diseases and aging:
Mitochondrial diseases represent a diagnostic challenge because of their wide variation in appearance and course. Organs and tissue frequently affected in mitochondrial diseases are the peripheral nervous system, brain, heart, eyes, ears, guts, kidney, and bone marrow. The genetic defects in patients suffering from mitochondrial diseases are either due to sporadic or inherited mutations in nuclear DNA (nDNA) or mitochondrial DNA (mtDNA) located genes. Mitochondrial diseases usually show a chronic, slowly progressive course and are characterized by multiorgan involvement with varying onset between birth and late adulthood. In a large number of cases the activity of the respiratory chain protein complexes is affected, leading to impaired oxygen metabolism, reduced energy production, and increased reactive oxygen species (ROS). To date there is no efficient therapy and cure for mitochondrial diseases and in order to develop better therapies it is necessary to know more about molecular mechanisms and mitochondrial proteins.
Mitochondria are the powerhouse for the generation of cellular energy pool and are important for a number of basic processes such as the regulation of energy homeostasis and programmed cell death. Research in mitochondria touches several disease-related fields at the clinical level, because mitochondrial dysfunction or mutations contribute to the ontogeny of cancer, diabetes, blindness, deafness, migraine, and diseases of the heart, kidney, liver, and muscles. Furthermore, mitochondrial dysfunction is involved in ageing and neurodegenerative disorders such as Parkinson's and Alzheimer's dementia. Because the foremost function of mitochondria is to generate cellular energy through oxidative phosphorylation, many of the tissues affected by mitochondrial diseases consist of cell types with a high demand of energy. Communication between the mitochondrial and nuclear genomes of eukaryotes is crucial for the normal coordination of mtDNA replication, as all factors necessary for this process are encoded in the nDNA. Furthermore, a balanced dNTP pool is essential for both normal nDNA and mtDNA replication and is tightly regulated by both the de novo and the salvage pathways for nucleotide biosynthesis.
- The role of deoxynucleoside kinases in maintaining genomic integrity
- Interaction between dNTP pools and mitochondrial function: basic research and aging
- The molecular mechanisms underlying mitochondrial-mediated mutagenesis
- Identification of proteins involved in maintaining integrity of the mitochondrial genome
- Fakouri NB, Durhuus JA, Regnell CE, Angleys M, Desler C, Hasan- Olive MDM, Martín-Pardillos A, Tsaalbi-Shtylik A, Thomsen K, Lauritzen M, Bohr VA, de Wind N, Bergersen LH, Rasmussen LJ. 2017. Rev1 contributes to proper mitochondrial function via the PARP-NAD+-SIRT1-PGC1α axis. Sci Rep. Oct 2;7(1):12480.
- Martín-Pardillos A, Tsaalbi-Shtylik A, Chen S, Lazare S, van Os RP, Dethmers-Ausema A, Fakouri NB, Bosshard M, Aprigliano R, van Loon B, Salvatori DCF, Hashimoto K, Dingemanse-van der Spek C, Moriya M, Rasmussen LJ, de Haan G, Raaijmakers MHG, de Wind N. 2017. Genomic and functional integrity of the hematopoietic system requires tolerance of oxidative DNA lesions. Blood. Sep 28;130(13):1523-1534.
- Thomsen K, Sherazi N, Yokota T, Hasan-Olive M, Fakouri NB, Desler C, Regnell C, Rasmussen LJ, Dela F, Bergersen LH, Lauritzen M. Initial brain aging: heterogeneity of mitochondrial size is associated with respiratory dysfunction in cortex and hippocampus. 2017. Neurobiol Aging. Aug 12. pii: S0197-4580(17)30259-2.
- Strickertsson J, Desler C, Rasmussen LJ. 2017. Bacterial infection increases risk of carcinogenesis by targeting mitochondria. Semin Cancer Biol. Jul 25. pii: S1044-579X(17)30192-X.
- Liu D, Keijzers G, Rasmussen LJ. 2017. DNA mismatch repair and its many roles in eukaryotic cells. Mutat Res Rev. 773:174-187.
Liu D, Frederiksen JH, Liberti SE, Lützen A, Keijzers G, Pena-Diaz J, Rasmussen LJ. 2017. Human DNA polymerase delta double-mutant D316A E318A interferes with DNA mismatch repair in vitro. Nucleic Acids Res. Sep 19;45(16):9427-9440.
Lopez-Contreras AJ, Specks J, Barlow JH, Ambrogio C, Desler C, Vikingsson S, Rodrigo-Perez S, Green H, Rasmussen LJ, Murga M, Nussenzweig A, Fernandez-Capetillo O. Increased Rrm2 gene dosage reduces fragile site breakage and prolongs survival of ATR mutant mice. Genes & Dev. 29: 690-695. 2015.
- Thompson BA, Spurdle AB, Plazzer J-P, et al. Application of a five-tiered scheme for standardized classification of 2,392 unique mismatch repair gene variants lodged on the InSiGHT locus-specific database. Nature Genetics. 46: 107-115. 2014.
- Maynard S, Keijzers G, Gram M, Desler C, Bendix L, Budtz-Jørgensen E, Molbo D, Croteau DL, Osler M, Stevsner T, Rasmussen LJ, Dela F, Avlund K, Bohr VA. Relationships between human vitality and mitochondrial respiratory parameters, reactive oxygen species and dNTP levels in peripheral blood mononuclear cells. Aging. 5: 850-864. 2014.
- Strickertsson JAB, Desler C, Rasmussen LJ. Impact of bacterial infections on aging and cancer: Impairment of DNA repair and mitochondrial function of host cells. Exp Gerontology. 56: 164-174. 2014.
- Machado AM, Desler C, Bøggild S, Strickertsson JA, Hansen LF, Figueiredo C, Seruca R, Rasmussen LJ. Helicobacter pylori infection affects mitochondrial function and DNA repair, thus, mediating genetic instability in gastric cells. Mech. Aging Dev. 134: 460-466. 2013.
- Drost M, Lützen A, van Hees S, Ferreira D, Calléja F, Zonneveld JBM, Nielsen FC, Rasmussen LJ, de Wind N. Genetic screens for the identification of pathogenic gene variants in the cancer predisposition Lynch syndrome. Proc. Natl. Acad. Sci. USA. 110: 9403-9408. 2013.
- Andersen SD, Liberti SE, Lützen A, Drost M, Bernstein I, Nilbert M, Dominguez M, Nyström M, Hansen TVO, Christoffersen JW, Jäger AC, de Wind N, Nielsen FC, Tørring PM, Rasmussen LJ. Functional characterization of MLH1 missense variants identified in Lynch Syndrome patients. Human Mutat. 33: 1647-1655. 2012.
- Rasmussen LJ, Heinen CD, Royer-Pokora B, Drost M, Tavtigian S, Hofstra RMW, de Wind N. Pathological assessment of mismatch repair gene variants in Lynch syndrome: past, present and future. Human Mutat. 33: 1617-1625. 2012.
- Machado AMD, Figueiredo C, Touati E, Máximo V, Sousa S, Michel V, Carneiro F, Nielsen FC, Seruca R, Rasmussen LJ. Helicobacter pylori infection induces genetic instability of nuclear and mitochondrial DNA in gastric cells. Clin. Cancer Res. 15: 2995-3002. 2009.
- Desler C, Petersen BM, Stevnsner T, Matsui S-I, Kulawiec M, Singh KK, Rasmussen LJ. Mitochondria as determinant of nucleotide metabolism and chromosomal stability. Mutat. Res. 625:112-124. 2007.