Stewart Michael K G, Plante Isabelle, Bechberger John F, Naus Christian C, Laird Dale W
Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada.
INRS-Institut Armand-Frappier, Laval, Québec, Canada.
PLoS One. 2014 Jul 2;9(7):e101546. doi: 10.1371/journal.pone.0101546. eCollection 2014.
Connexin26 (Cx26) is the major Cx protein expressed in the human mammary gland and is up-regulated during pregnancy while remaining elevated throughout lactation. It is currently unknown if patients with loss-of-function Cx26 mutations that result in hearing loss and skin diseases have a greater susceptibility to impaired breast development. To investigate if Cx26 plays a critical role in mammary gland development and differentiation, a novel Cx26 conditional knockout mouse model was generated by crossing Cx26fl/fl mice with mice expressing Cre under the β-Lactoglobulin promoter. Conditional knockdown of Cx26 from the mammary gland resulted in a dramatic reduction in detectable gap junction plaques confirmed by a significant ∼65-70% reduction in Cx26 mRNA and protein throughout parturition and lactation. Interestingly, this reduction was accompanied by a decrease in mammary gland Cx30 gap junction plaques at parturition, while no change was observed for Cx32 or Cx43. Whole mount, histological and immunofluorescent assessment of breast tissue revealed comparatively normal lobuloalveolar development following pregnancy in the conditionally knockdown mice compared to control mice. In addition, glands from genetically-modified mice were capable of producing milk proteins that were evident in the lumen of alveoli and ducts at similar levels as controls, suggesting normal gland function. Together, our results suggest that low levels of Cx26 expression throughout pregnancy and lactation, and not the physiological surge in Cx26, is sufficient for normal gland development and function.
连接蛋白26（Cx26）是人类乳腺中表达的主要连接蛋白，在怀孕期间上调，并在整个哺乳期保持高水平。目前尚不清楚导致听力丧失和皮肤病的功能丧失型Cx26突变患者是否更容易出现乳腺发育受损。为了研究Cx26在乳腺发育和分化中是否起关键作用，通过将Cx26fl/fl小鼠与在β-乳球蛋白启动子下表达Cre的小鼠杂交，构建了一种新型的Cx26条件性敲除小鼠模型。从乳腺中条件性敲低Cx26导致可检测到的间隙连接斑块显著减少，在整个分娩和哺乳期，Cx26 mRNA和蛋白显著减少约65 - 70%证实了这一点。有趣的是，这种减少伴随着分娩时乳腺Cx30间隙连接斑块的减少，而Cx32或Cx43未观察到变化。对乳腺组织进行的整体、组织学和免疫荧光评估显示，与对照小鼠相比，条件性敲低小鼠在怀孕后小叶腺泡发育相对正常。此外，转基因小鼠的腺体能够产生乳蛋白，在肺泡和导管腔中与对照小鼠水平相似，表明腺体功能正常。总之，我们的结果表明，在整个怀孕和哺乳期低水平的Cx26表达，而不是Cx26的生理性激增，足以实现正常的腺体发育和功能。
