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Chromosome Biology Laboratory

PI- Ciaran Morrison

We are interested in a number of mechanisms and cellular processes that ensure the accurate transmission of the genome during cell division. Loss or gain of genetic information is a key early step in cancer development. However, DNA damage can kill cells and thus, many of the most effective anticancer therapies rely on inducing genotoxic stresses in cells. Our current research themes are:
1. The control mechanisms for centrosome duplication.
2. How telomere structure is involved in chromosome stability.
3. Key proteins in the DNA damage response- Mcph1 and Smc5-6.
In exploring these questions, we use cell biology, reverse genetic and biochemical approaches in human and chicken tissue culture cell lines.

Dissection of the mechanisms controlling centrosome number

The centrosome is the key microtubule organising centre of animal cells. Centrosomes define the mitotic spindle and play a critical role in cell division. Centrosome duplication is normally tightly controlled and linked to the progression of the cell cycle. Abnormal amplification of centrosomes is a feature of tumour cells and has been observed after irradiation, incomplete DNA replication and in cells that carry mutations in DNA repair genes.


HCC1937 breast cancer cells. Antibodies to alpha-tubulin (red) stain the microtubules, and to gamma-tubulin (green), the centrosomes. DNA is shown in blue. (Pic. Chiara Saladino)	Multipolar mitosis in an irradiated U2OS osteosarcoma cell. Antibodies to alpha-tubulin (red) stain the spindle and to gamma-tubulin (green), the centrosomes. DNA is shown in blue. (Pic. Helen Dodson).	Human U2OS osteosarcoma cell expressing histone H2B-RFP (red) and GFP-centrin1 (green). Following irradiation this mitotic cell has multiple centrosomes. (Pic. Helen Dodson).

Using light and electron microscopy of human cells, Emer Bourke, Helen Dodson and Lorraine Cuffe (in collaboration with Andreas Merdes, CNRS Toulouse and David Gillespie, Beatson Inst., Glasgow) showed that ATM and ATR act in a complementary fashion to allow centrosome amplification after DNA damage, but that Chk1 kinase activity is necessary for this to occur. Emer used reverse genetics to show that Chk1 acts through controlling the cell cycle regulator Cdk2-cyclin E, linking the centrosome response to DNA damage. To visualise centrosome duplication using timelapse microscopy, Helen has generated human cell lines that stably express fluorescently-tagged cell cycle and centrosome markers. In collaboration with Sally Wheatley (University of Sussex), we are using these cells to make movies of how centrosomes respond to DNA damage. Chiara Saladino has just joined and is beginning to explore how centrosomes respond to DNA damage in breast cancer cells.

U2OS cells showing centrosome amplification following treatment with ionising radiation. The centrosomes are visualised using a gamma tubulin antibody (red) and the microtubules are stained in green. DNA is shown in blue. (Pic. Helen Dodson).

Role of telomeres in maintenance of genome stability

The ends of linear eukaryotic chromosomes are capped by specialised nucleoprotein structures termed telomeres. Telomeres protect against chromosome degradation, rearrangement, and chromosomal fusion events. Using reverse genetics and microscopy of tissue culture cells, Virginie Faure and Carol Cooley are examining how certain key genes are involved in telomere structure. We have successfully generated Trf1-deficient DT40 cells and are analysing them. We have found that the loss of even one allele of the telomerase RNA, Terc , in Ku- deficient cells results in a cell cycle arrest that appears to involve a DNA damage signal at telomeres, suggesting that Ku is involved in preventing telomere ends from generating such signals when telomerase activity declines.

Telomere repeat binding factor 2 (green) localising to telomeric DNA sequences (red) in a chicken DT40 cell. DNA is shown in blue. (Pic. Carol Cooley).

Mechanistic analyses of the DNA damage response

Structural maintenance of chromosome (Smc) family members are involved in a range of activities that contribute to ensuring accurate duplication of the chromosomes. Anna Stephan is investigating the roles of the Smc5-6 complex in DNA repair and mitosis, using reverse genetics and biochemistry.

Microcephalin (Mcph1) is encoded by a gene mutated in the autosomal recessive disease, primary microcephaly. Liam Jeffers, Barry Coull and Séamus Stack are examining how Mcph1 is involved in a range of activities that maintain genome stability, including the response to DNA damage, the duplication of the centrosome and the compaction of chromosomes that occurs before cells can divide.

Colocalisation of GFP-Mcph1 (green) with gamma-H2AX (red) in irradiation-induced foci in chicken DT40 cells. (Pic. Liam Jeffers).

These different research strands are aimed at understanding the key mechanisms that ensure that cells keep their genomes intact. This understanding will allow us to see how certain genes are involved in causing cancer and may allow us to identify particular targets that may be worth targeting with drugs to try and kill tumour cells.

Lab members


The lab photographed in the Quadrangle, NUIG. Left to right: Ciaran, Lorraine (seconded from Samali group), Anna, Helen, Emer, Virginie, Liam and Carol.

The lab and cherry blossoms.

Members of the group in Yosemite National Park, after presenting their work at the American Society for Cell Biology Annual Meeting in San Francisco, December 2005. L-R, Helen, Ciaran, Liam, Emer and Anna.

Funding

Work in the lab is funded by Science Foundation Ireland. http://www.sfi.ie/

Positions available

Openings for postdoctoral fellows with interests/ experience in DNA repair and chromosome biology and for students with similar interests arise sporadically. Please contact Ciaran Morrison at ciaran.morrisonnuigalway.ie for further details.

Biochemistry, School of Natural Science.
National University of Ireland, Galway, University Road, Galway, Ireland.
Phone: +353 (0)91 492420
E-mail: Biochemistry
This page was last updated Monday, July 21, 2008