Developmental expression patterns and regulation of connexins in the mouse mammary gland: expression of connexin30 in lactogenesis.
The mammary gland reaches a fully differentiated phenotype at lactation, a stage characterized by the abundant expression of beta-casein. We have investigated the expression and regulation of gap junction proteins (connexins, Cx) during the various developmental stages of mouse mammary gland. Immunohistochemical analysis, with specific antibodies, reveals that Cx26 and Cx32 are expressed and confined to the cell borders of luminal epithelial cells in all developmental stages of the gland. Cx26 and Cx32 expression, at the mRNA and protein levels, increases in pregnancy and peaks in lactation. Whereas Cx43 mRNA decreases in pregnancy and lactation, the functional activity of Cx43 protein, which has been localized to myoepithelial cells, is regulated (through phosphorylation) during pregnancy and peaks during lactation. Cx30 mRNA and proteins have, for the first time, been detected in mammary gland epithelia. Using reverse transcription/polymerase chain reaction and sequencing techniques, we show that Cx30 is abundant in pregnant and lactating mammary gland. Cx30 protein levels have not been detected in the mammary gland prior to day 15 of pregnancy, whereas maximum expression occurs at the onset of lactation. In mouse mammary cells in culture, Cx30 is epithelial-cell-specific and is induced by lactogenic hormones. These data identify a novel player in mammary differentiation and suggest a potential role for Cx30 in the fully differentiated gland.
Talhouk
Rabih S
RS
Department of Biology, Faculty of Arts and Sciences, American University of Beirut, PO Box 11-0236, Beirut, Lebanon. rtalhouk@aub.edu.lb
Elble
Randolph C
RC
Bassam
Rola
R
Daher
Mariam
M
Sfeir
Agnel
A
Mosleh
Lina Abi
LA
El-Khoury
Hilda
H
Hamoui
Samar
S
Pauli
Bendicht U
BU
El-Sabban
Marwan E
ME
D000818:Animals; D002454:Cell Differentiation; D000072259:Connexin 26; D000075302:Connexin 30; D018031:Connexin 43 / Q000096:biosynthesis; D017630:Connexins / Q000096:biosynthesis*; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D017629:Gap Junctions / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D007150:Immunohistochemistry; D007774:Lactation; D008321:Mammary Glands, Animal / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D011247:Pregnancy; D000097002:Gap Junction beta-1 Protein
D000072259:Connexin 26; D000075302:Connexin 30; D018031:Connexin 43; D017630:Connexins; D000097002:Gap Junction beta-1 Protein; C100629:Gjb6 protein, mouse