Dataset Information

Developmental regulation of Bcl-2 family protein expression in the involuting mammary gland.

ABSTRACT: Epithelial cells within the mammary gland undergo developmental programmes of proliferation and apoptosis during the pregnancy cycle. After weaning, secretory epithelial cells are removed by apoptosis. To determine whether members of the Bcl-2 gene family could be involved in regulating this process, we have examined whether changes in their expression occur during this developmental apoptotic program in vivo. Bax and Bcl-x were evenly expressed throughout development. However, expression of Bak and Bad was increased during late pregnancy and lactation, and the proteins were present during the time of maximal apoptotic involution. Thereafter, their levels declined. In contrast, Bcl-w was expressed in pregnancy and lactation but was downregulated at the onset of apoptosis. Bcl-2 was not detected in lactating or early involuting mammary gland. Thus, the pro-apoptotic proteins Bax, Bak and Bad, as well as the death-suppressors Bcl-x, Bcl-2 and Bcl-w, are synthesised in mouse mammary gland, and dynamic changes in the expression profiles of these proteins occurs during development. To determine if changes in Bak and Bcl-w expression could regulate mammary apoptosis, their effect on cultured mouse mammary epithelial cells was examined in transient transfection assays. Enforced expression of Bak induced rapid mammary apoptosis, which could be suppressed by coexpression of Bcl-w. In extracts of mammary tissue in vivo, Bak heterodimerized with Bcl-x whereas Bax associated with Bcl-w, but Bak/Bcl-w heterodimers were not detected. Thus, Bak and Bcl-w may regulate cell death through independent pathways. These results support a model in which mammary epithelial cells are primed for apoptosis during the transition from pregnancy to lactation by de novo expression of the death effectors Bak and Bad. It is suggested that these proteins are prevented from triggering apoptosis by anti-apoptotic Bcl-2 family proteins until involution, when the levels of Bcl-w decline. Our study provides evidence that regulated changes in the expression of cell death genes may contribute to the developmental control of mammary apoptosis.

SUBMITTER: Metcalfe AD

PROVIDER: S-EPMC3049815 | biostudies-literature | 1999 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Developmental regulation of Bcl-2 family protein expression in the involuting mammary gland.

Metcalfe A D AD Gilmore A A Klinowska T T Oliver J J Valentijn A J AJ Brown R R Ross A A MacGregor G G Hickman J A JA Streuli C H CH

Journal of cell science 19990601

Epithelial cells within the mammary gland undergo developmental programmes of proliferation and apoptosis during the pregnancy cycle. After weaning, secretory epithelial cells are removed by apoptosis. To determine whether members of the Bcl-2 gene family could be involved in regulating this process, we have examined whether changes in their expression occur during this developmental apoptotic program in vivo. Bax and Bcl-x were evenly expressed throughout development. However, expression of Bak ...[more]

PMID: 10318769

Similar Datasets

Project description:Claudins are a large family of membrane proteins whose classic function is to regulate the permeability of tight junctions in epithelia. They are tetraspanins, with four alpha-helices crossing the membrane, two extracellular loops, a short cytoplasmic N-terminus and a longer and more variable C-terminus. The extracellular ends of the helices are known to undergo side-to-side (cis) interactions that allow the formation of claudin polymers in the plane of the membrane. The extracellular loops also engage in head-to-head (trans) interactions thought to mediate the formation of tight junctions. However, claudins are also present in intracellular structures, thought to be vesicles, with less well-characterized functions. Here, we briefly review our current understanding of claudin structure and function followed by an examination of changes in claudin mRNA and protein expression and localization through mammary gland development. Claudins-1, 3, 4, 7, and 8 are the five most prominent members of the claudin family in the mouse mammary gland, with varied abundance and intracellular localization during the different stages of post-pubertal development. Claudin-1 is clearly localized to tight junctions in mammary ducts in non-pregnant non-lactating animals. Cytoplasmic puncta that stain for claudin-7 are present throughout development. During pregnancy claudin-3 is localized both to the tight junction and basolaterally while claudin-4 is found only in sparse puncta. In the lactating mouse both claudin-3 and claudin-8 are localized at the tight junction where they may be important in forming the paracellular barrier. At involution and under challenge by lipopolysaccharide claudins -1, -3, and -4 are significantly upregulated. Claudin-3 is still colocalized with tight junction molecules but is also distributed through the cytoplasm as is claudin-4. These largely descriptive data provide the essential framework for future mechanistic studies of the function and regulation of mammary epithelial cell claudins.

Project description:Mammary gland involution represents one of the most dramatic examples of programmed cell death/apoptosis and tissue regression during development, yet large gaps still exist in the understanding of the mechanisms involved, and the key factors that trigger involution, are not yet identified. With the focus on identifying “novel” genes associated with mammary gland regression, we used microarray analysis to examine differentially expressed genes during early mammary gland involution in the mouse. We believe that such analysis may facilitate the identification of genes that report on proliferative changes in the breast, particularly with regards to growth arrest and growth inhibition. We further reasoned that genes that inhibit mammary gland proliferation might have relevance to breast tumorigenesis since cancer is generally associated with a defect in apoptosis and cell growth arrest. Gene expression from day 0 (D0) of involution was compared to day 1 (D1, 24 hr post weaning) to identify genes exhibiting differential expression. A total of 5,826 genes were identified as being differentially expressed. Changes in gene expression were confirmed by quantitative real time PCR analysis of 21 randomly selected genes. Following the selection of a number of highly regulated mouse genes within this cohort, database searches were then employed to identify genes associated with human tumorigenesis. With an ultimate goal being the identification of genes, which under normal physiological conditions, inhibit breast proliferation, and therefore have the potential to impact on the clinical management of breast cancer, we further examined their relevance to human tumorigenesis. Among genes identified as having human homologues, and with previously established links to human tumorigenesis, were several known genes among the top 200 differentially expressed genes including EGF, EGFR, TGFß2, PTHLH, IGFBP1, that were down regulated. Upregulated known genes included ANNEXIN A1 and A3, THYMOSIN BETA 10, IGFBP5, LIF, BID, BCL2, JUN, KIT, and CLAUDIN 1. CLAUDIN 1 was the most highly upregulated gene in our dataset. Moreover, we identified a number of genes not previously implicated or not well characterized in human breast cancer including ANGPTL4, SLC34A2, GOS2, STEAP, SOX4, TNFRSF12A and SAA2. The expression levels of these genes in human breast cancer were confirmed in breast cancer cell lines and breast tumor tissues. For some of these genes, expression was consistently down regulated in a small panel of human breast tumor specimens. We believe that these genes now warrant further investigation to determine their relevance to human breast tumorigenesis and their potential utility as therapeutic targets for human breast cancer. This pilot study was used to demonstrate proof of principle that through the analysis of gene expression during mammary gland involution, it may be indeed possible to identify “novel” genes relevant to the growth arrest in the mammary gland and relevant to human breast cancer. Keywords: comparative expression analysis of involuting mouse mammary gland

Dataset Information

Developmental regulation of Bcl-2 family protein expression in the involuting mammary gland.

Publications

Developmental regulation of Bcl-2 family protein expression in the involuting mammary gland.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets