DNA damage response, Pluripotency, Reprogramming, haematological disorders, leukaemia, conditional knock out, bone marrow transplants, derivation of ESCs.
B-Myb and genome stability in mESCs
B-Myb is a ubiquitously expressed member of the myb proto-oncogene family known to be amplified in several types of tumours such as neuroblastoma, breast cancer and ovarian cancer. It has also been shown that reduced levels can lead to chromosome instability, a hallmark of cancer. These findings point at a dual role of B-Myb as an oncogene and also as a tumour suppressor. We have recently demonstrated using single DNA-fibre techniques that B-Myb ablation leads to chromosome instability by affecting replication dynamics in somatic and embryonic stem cells. Also, there is a significant accumulation in dsDNA breaks during the normal replication cycle in the absence of DNA damage as well as 24h after irradiation. DNA lesions are a normal occurrence during the replication of the genome, but failing to repair those results in mutations, genome instability and cell death. Our data indicates that cells lacking B-Myb are inefficient in repairing their DNA, leading to accumulation of lesions and genome instability.
We hypothesise that B-Myb acts as a key protein safeguarding chromosome stability. Our research focuses on elucidating how B-Myb influences DNA replication, particularly in relation to its roles at the intra S-phase checkpoint, and in replication fork-progression, DNA repair and telomere maintenance.
B-Myb in haematological disorders during ageing
Paloma is also interested in studying the role of the transcription factor B-Myb in the development of haematological disorders such as leukaemia, myelodysplasia and myeloproliferative disorders.
Blood disorders are a common feature of ageing. Statistics show that more than 62% of people diagnosed with myeloid dysplastic syndrome (MDS), myeloid proliferative disorder (MPD) and leukaemia fall within the age group over 60 years. One theory suggests that during the life of an individual, DNA mutations accumulate in the genome during the cell replicative process due to failure in repair mechanisms, leading to either activation of oncogenes or silencing of tumour suppressors, hence establishing the onset of the disease.
A percentage of patients with MDS, MPD and myeloid leukaemia present cytogenetic abnormalities that include deletion of the long arm of chromosome 20 (del20q), which includes the region encoding B-Myb. It has been proposed that one or more genes from this region could be acting as tumour suppressors, and that deletion of the gene(s) will favour the onset or progression of the disease. The identity of the gene(s) responsible for the disease association is unknown.
Using genetic engineering, Paloma has generated a mouse model of B-Myb haploinsufficiency in which one allele of the B-Myb gene is deleted (B-Myb+/D). We have kept a cohort of 24 mice (11 wt and 13 B-Myb+/D) for 22 months, after which time 12 out of 13 B-Myb+/D mice (92%) developed blood disorders (leukaemia, MPD and MDS), compared to 1 out of 11 wt littermates (9%). We have also demonstrated that under replicative stress conditions, animals transplanted with B-Myb+/D cells developed haematological disorders more rapidly (after 8 months).
This novel data indicates that B-Myb is a strong candidate for the gene responsible for the pathological consequences of del20q.
Derivation of embryonic stem cells and iPScs generation
Paloma has been the first researcher in Birmingham University to derive embryonic stem cells from blastocysts of genetically modified mice. Her expertise in ESCs culture maintenance and derivation as well as conditional knock-out generation has resulted in her being the person of reference for other groups wishing to generate ESCs from knock out models. Also, Paloma has been instrumental in setting up the generation of induced pluripotent stem cells from mouse fibroblasts, and advices research from other groups aiming to generate human iPSCs.