Biology subjects

Hirst, M.

Publications and source records attributed to Hirst, M..

3 recordsLinked to original sources

bioRxiv2018

Epiclomal: probabilistic clustering of sparse single-cell DNA methylation data

We present Epiclomal, a probabilistic clustering method arising from a hierarchical mixture model to simultaneously cluster sparse single-cell DNA methylation data and impute missing values. Using synthetic and published single-cell CpG datasets we show that Epiclomal outperforms non-probabilistic methods and is able to handle the inherent missing data feature which dominates single-cell CpG genome sequences. Using a recently published single-cell 5mCpG sequencing method (PBAL), we show that Epiclomal discovers sub-clonal patterns of methylation in aneuploid tumour genomes, thus defining epiclones. We show that epiclones may transcend copy number determined clonal lineages, thus opening this important form of clonal analysis in cancer. Epiclomal is written in R and Python and is available at https://github.com/shahcompbio/Epiclomal.

genomics↗

bioRxiv2018

MeCP2-E1 isoform is a dynamically expressed, weakly DNA-bound protein with different protein and DNA interactions compared to MeCP2-E2

MeCP2 - a chromatin-binding protein associated with Rett syndrome - has two main isoforms, MeCP2-E1 and MeCP2-E2, with 96% amino acid identity differing in a few N-terminal amino acid residues. Previous studies have shown brain region-specific expression of these isoforms which, in addition to their different cellular localization and differential expression during brain development, suggest they may also have non-overlapping molecular mechanisms. However, differential functions of MeCP2-E1 and E2 remain largely unexplored. Here, we show that the N-terminal domains (NTD) of MeCP2-E1 and E2 modulate the ability of the methyl binding domain (MBD) to interact with DNA as well as influencing the turnover rates, binding dynamics, response to nuclear depolarization, and circadian oscillations of the two isoforms. Our proteomics data indicate that both isoforms exhibit unique interacting protein partners. Moreover, genome-wide analysis using ChIP-seq provide evidence for a shared as well as a specific regulation of different sets of genes. Our findings provide insight into the functional complexity of MeCP2 by dissecting differential aspects of its two isoforms.\n\nSignificanceWhether the two E1 and E2 isoforms of MeCP2 have different structural and/or functional implications has been highly controversial and is not well known. Here we show that the relatively short N-terminal sequence variation between the two isoforms impinges them with an important DNA binding difference. Moreover, MeCP2-E1 and E2 exhibit a different cellular dynamic behavior and have some distinctive interacting partners. In addition, while sharing genome occupancy they specifically bind to several distinctive genes.

biochemistry↗

bioRxiv2018

YB-1 Is Critical For The Genesis And Progression Of KRAS Mutated Human Breast Cancer

Breast cancer heterogeneity has made it challenging to elucidate shared mechanisms that underpin properties that are critical to their growth in vivo. Here, we interrogate the role of YB-1 protein in the in vivo tumorigenic activity of de novo well as cell line models of human breast cancer. Short-hairpin RNA-mediated knockdown of YB-1 in MDA-MB-231 cells blocked both their local tumour-forming and lung-colonizing activity in transplanted immunodeficient mice. YB-1 knockdown also revealed its important role at early stages of human mammary cell transformation in the generation of invasive ductal carcinoma and ductal carcinoma in situ produced in mice transplanted with freshly isolated human mammary cells transduced, respectively, with KRASG12D, or myristoylated-AKT1. Conversely, upregulated expression of YB-1 in the poorly tumorigenic T47D cells enhanced this activity. Mechanistically, reducing YB-1 levels in MDA-MB-231 cells impaired their induction of HIF1, and G3BP1, known YB-1 translational targets and key elements of a stress-adaptive program.

cancer biology↗