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Deficiency of lysyl hydroxylase 2 in mice causes systemic endoplasmic reticulum stress leading to early embryonic lethality

Kasamatsu, Atsushi, Uzawa, Katsuhiro, Hayashi, Fumihiko, Kita, Akihiro, Okubo, Yasuhiko, Saito, Tomoaki, Kimura, Yasushi, Miyamoto, Isao, Oka, Noritoshi, Shiiba, Masashi, Ito, Chizuru, Toshimori, Kiyotaka, Miki, Takashi, Yamauchi, Mitsuo, Tanzawa, Hideki
Biochemical and biophysical research communications 2019 v.512 no.3 pp. 486-491
animal models, apoptosis, bone formation, caspase-3, catalytic activity, collagen, crosslinking, death, endoplasmic reticulum, endoplasmic reticulum stress, fibrosis, gene expression regulation, gene targeting, genes, genotyping, heart, homozygosity, hydroxylation, immunohistochemistry, knockout mutants, lysine, metastasis, mice, neoplasms, reverse transcriptase polymerase chain reaction
Lysyl hydroxylase 2 (LH2) is an endoplasmic reticulum (ER)-resident enzyme that catalyzes the hydroxylation of lysine residues in the telopeptides of fibrillar collagens. This is a critical modification to determine the fate of collagen cross-linking pathway that contributes to the stability of collagen fibrils. Studies have demonstrated that the aberrant LH2 function causes various diseases including osteogenesis imperfecta, fibrosis, and cancer metastasis. However, surprisingly, a LH2-deficient animal model has not been reported. In the current study, to better understand the function of LH2, we generated LH2 gene knockout mice by CRISPR/Cas9 technology. LH2 deficiency was confirmed by genotyping polymerase chain reaction (PCR), reverse transcriptase-PCR, and immunohistochemical analyses. Homozygous LH2 knockout (LH2−/−) embryos failed to develop normally and died at early embryonic stage E10.5 with abnormal common ventricle in a heart, i.e., an insufficient wall, a thin ventricular wall, and loosely packed cells. In the LH2−/− mice, the ER stress-responsive genes, ATF4 and CHOP were significantly up-regulated leading to increased levels of Bax and cleaved caspase-3. These data indicate that LH2 plays an essential role in cardiac development through an ER stress-mediated apoptosis pathway.