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11 December 2018 Seipin deficiency leads to increased endoplasmic reticulum stress and apoptosis in mammary gland alveolar epithelial cells during lactation
Ahmed E. El Zowalaty, Rong Li, Weiqin Chen, Xiaoqin Ye
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Abstract

Seipin is an integral endoplasmic reticulum (ER) membrane protein encoded by Berardinelli– Seip congenital lipodystrophy type 2 (BSCL2/Bscl2) gene. Most litters (59%) from Bscl2-/- dams mated with wild type (WT) (Bscl2+/+) males did not survive postnatal day 5 (PND5) and pups (Bscl2+/-) lacked milk in their stomachs. The survived litters had reduced pup survival rate at PND21. It was hypothesized that seipin was critical for lactation. Bscl2 was upregulated and highly detected in the lactation day 1 (LD1) WT mammary gland alveolar epithelial cells. LD1 Bscl2-/- mammary glands lacked adipocytes and alveolar clusters and had varied alveolar morphology: from interconnected mammary gland alveoli with dilated lumen and sloughed epithelial cells to undifferentiated mammary gland alveoli with unexpanded lumen. Comparable levels of whey acidic protein (WAP, a major component in rodent milk) staining and Nile Red lipid droplet staining between WT and Bscl2-/- LD1 alveolar epithelial cells indicated normal milk protein synthesis and lipid syntheses in LD1 Bscl2-/- mammary glands. Significantly reduced percentage of larger lipid droplets was detected in LD1 Bscl2-/- alveoli with unexpanded lumen. There was no obviously impaired proliferation detected by PCNA staining but increased apoptosis detected by cleaved caspase-3 staining in LD1 Bscl2-/- alveolar epithelial cells. Increased expression of protein disulfide isomerase and binding immunoglobulin protein in the LD1 Bscl2-/- mammary gland alveolar epithelial cells indicated increased ER stress. This study demonstrates increased ER stress and apoptosis in LD1 Bscl2-/- mammary gland alveolar epithelial cells and reveals a novel in vivo function of seipin in lactation.

Summary Sentence

Our findings that pups from Bscl2-/- dams lacked milk and had reduced survival rate as well as that LD1 Bscl2-/- mammary gland alveolar epithelial cells had increased ER stress and apoptosis reveal a novel in vivo function of seipin in lactation.

© The Author(s) 2017. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com
Ahmed E. El Zowalaty, Rong Li, Weiqin Chen, and Xiaoqin Ye "Seipin deficiency leads to increased endoplasmic reticulum stress and apoptosis in mammary gland alveolar epithelial cells during lactation," Biology of Reproduction 98(4), 570-578, (11 December 2018). https://doi.org/10.1093/biolre/iox169
Received: 25 November 2017; Accepted: 10 December 2017; Published: 11 December 2018
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