Charting cellular changes in the human breast associated with embryogenesis, parity, age, menopause and germline mutations

Each organ in our body is composed of millions of cells. However, not all the cells within an organ are the same, they all have a defined role and fate which cumulatively dictates the function of the organ. The mammary gland is one of the defining organs that distinguishes mammals from other organisms. The primary role of the mammary gland is to produce and secrete milk to nurture new-born mammals. Just like any other organ, the mammary gland is composed of multiple cell types each with a defined role and fate. Understanding how these different cell types relate to each other and contribute to development of disease is required. It is only within the last 5 years has it become technically feasible to identify which genes are active within a single cell. We have recently used this novel technology to profile 23,000 individual mouse mammary cells and determine their identity and chart their fate. We found that we can divide the 23,000 cells in to 15 different groups based on their identity. Based on this successful study we propose here to use the same technology to study human breast cells. We aim to analyse cells isolated from different women with a view of capturing changes in the breast tissue mediated by age, lactation, menopause and genetic mutations such as Brca1/2. This is will be useful information as it is known that the risk of developing breast cancer is increased with age and reduced with pregnancy. Therefore, data from our study will shed light on the cellular changes associated with these different breast cancer risk modulators

One of the biggest challenges in treating breast cancer is the heterogenous nature of the disease which is initiated by oncogenic events in a tumour initiating cells. To fully understand the contribution of the cell of origin to this heterogeneity we must first comprehensively identify the different cell types found in the breast and map how they change in response to various developmental processes. We propose here to use single cell sequencing approaches to identify and chart the differentiation dynamics of epithelial and non-epithelial breast cells during embryonic development and in response to aging, parity, lactation, menopause and germline mutations. We will use two types of single cell sequencing approaches to tackle this problem; scRNAseq and scATACseq. The scRNAseq data will allow us to identify the different types of cells found in the breast across these different developmental conditions while scATACseq will allow us to identify changes in the chromatin accessibility states of these different cell clusters thus, indicating a switch in the epigenetic identity of the cell. Therefore, if awarded, this grant will allow us to generate a comprehensive Human Breast Cell Atlas which will provide the breast cancer research community with an unparalleled resource to accelerate the discovery of novel biomarkers and mechanisms behind breast cancer development.

Who might benefit from this research?
1) Mammary gland biology field
2) Stem cell biologists
3) Developmental biologists
4) Clinical researchers

How might they benefit from this research?
1) Novel understanding and new knowledge of how the human breast cellular homeostasis takes place in response to age, parity, menopause, and gremline mutations.
2) Potential for novel biomarkers being identified thus aiding earlier diagnosis of disease.
3) Generating large publically available scRNAseq datasets which can be mined by researchers in the future.