|CHENG, ADRIENNE - University Of Wisconsin|
|HERNANDEZ, LAURA - University Of Wisconsin|
Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2021
Publication Date: 8/26/2021
Citation: Cheng, A., Li, W., Hernandez, L. 2021. Investigating the effect of positional variation on mid-lactation mammary gland transcriptomics in mice fed either a low-fat or high-fat diet. PLoS ONE. 16(8): e0255770. https://doi.org/10.1371/journal.pone.0255770.
Interpretive Summary: The mouse has been routinely used as a model species to study the physiological changes in the mammary glands in response to diet. Like most mammals, mice develop their mammary glands in pairs with the two counterparts symmetrically displaced away from the ventral midline. Due to this symmetry and the same functional role as a milk-producing organ, each of the mammary glands of mice have been assumed to be the same with respect to physiology and response to environmental changes such as changes to diet. In this study, we investigated the impact of the mammary gland location and dietary intake on gene expression in the mouse model during mid-lactation. Twelve 3-week old C57BL/6 mice were randomly assigned to either a low-fat diet or high-fat diet. After a loading period of 5 weeks on the diet, mice were initially bred overnight with a male at 8 weeks of age. The pregnant mice were kept for further studies. At lactation day 11, the right thoracic or inguinal mammary gland was collected from each dam (n=3 per group) and gene expression in the collected tissue was analyzed by RNA-seq. Our study demonstrates that collection of the mammary gland from a particular location influences mammary gland gene expression. These findings will be useful for researchers studying lactation, highlighting the importance of considering this effect when designing experiments, as well as showing the need to properly document and report which mammary gland they are using for their studies.
Technical Abstract: Little attention has been given to the effect of positional variation of gene expression in the mammary gland. However, more research is shedding light regarding the physiological differences that mammary gland location can have on the murine mammary gland. Here we examined the potential interaction between mammary gland position and dam dietary intake on gene expression changes in the mid-lactation mammary gland (lactation day 11; L11). Twelve 3-week old wild type, female C57BL/6 mice were randomly assigned to either a low-fat diet (LFD) or high fat diet (HFD) (n=3/group). After a loading period of 5 weeks on the diet, mice were initially bred overnight with a male at 8 weeks of age. The pregnant mice were kept for further studies. At lactation day 11, either the right thoracic mammary gland (TMG) or inguinal mammary gland (IMG) was collected from each dam. Differentially expressed genes (DEGs) were first filtered by adjusted p-value (cutoff of 0.05) and fold-change (FC, cutoff >2). Genes were further filtered by mean normalized read count (cutoff of 10. We observed that mammary gland position had a more significant impact on mammary gland gene expression than diet, with 1264 DEGs in LFD dams and 777 DEGs in HFD dams. We demonstrated that genes related to snRNP binding and translation initiation were most significantly altered between the TMG and IMG. Although we were not able to discern a molecular mechanism, many small nuclear RNAs and small nucleolar RNAs were differentially expressed between the TMG and IMG which are responsible for cellular functions such as splicing and ribosome biogenesis which provides an interesting avenue for future research. Our study demonstrates that collection of the mammary gland from a particular location influences mammary gland gene expression, thereby highlighting the importance for researchers to be vigilant in documenting and reporting which mammary gland they are using for their studies.