NCBI Summary:
The activity of nonmuscle myosin II (see MYH9; MIM 160775) is regulated by phosphorylation of a regulatory light chain, such as MRLC2. This phosphorylation results in higher MgATPase activity and the assembly of myosin II filaments (Iwasaki et al., 2001 [PubMed 11942626]).[supplied by OMIM, Mar 2008]
General function
Cytoskeleton
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Cellular localization
Cytoplasmic
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Ovarian function
Oocyte maturation
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Cortical mechanics and myosin-II abnormalities associated with post-ovulatory aging: Implications for functional defects in aged eggs. Mackenzie AC et al. (2016) Cellular aging of the egg following ovulation, also known as post-ovulatory aging, is associated with aberrant cortical mechanics and actomyosin cytoskeleton functions. Post-ovulatory aging is associated with dysfunction of non-muscle myosin-II, and pharmacologically-induced myosin-II dysfunction produces some of the same deficiencies observed in aged eggs. Reproductive success is reduced with delayed fertilization and when copulation or insemination occurs at increased times after ovulation. Post-ovulatory aged eggs have several abnormalities in the plasma membrane and cortex, including reduced egg membrane receptivity to sperm, aberrant sperm-induced cortical remodeling and formation of fertilization cones at the site of sperm entry, and reduced ability to establish a membrane block to prevent polyspermic fertilization. Ovulated mouse eggs were collected at 21-22 hr post-hCG (aged eggs) or at 13-14 h post-hCG (young eggs), or young eggs were treated with the myosin light chain kinase (MLCK) inhibitor ML-7, to test the hypothesis that disruption of myosin-II function could mimic some of the effects of post-ovulatory aging. Eggs were subjected to various analyses. Cytoskeletal proteins in eggs and parthenogenesis were assessed using fluorescence microscopy, with further analysis of cytoskeletal proteins in immunoblotting experiments. Cortical tension was measured through micropipette aspiration assays. Egg membrane receptivity to sperm was assessed in in vitro fertilization (IVF) assays. Membrane topography was examined by low-vacuum scanning electron microscopy. Aged eggs have decreased levels and abnormal localizations of phosphorylated myosin-II regulatory light chain (pMRLC; p=0.0062). Cortical tension, which is mediated in part by myosin-II, is reduced in aged mouse eggs as compared to young eggs, by ∼40% in the cortical region where the metaphase II spindle is sequestered, and by ∼50% in the domain to which sperm bind and fuse (p<0.0001). Aging-associated parthenogenesis is partly rescued by treating eggs with a zinc ionophore (p=0.003), as is parthenogenesis induced by inhibition of mitogen-activated kinase (MAPK) 3/1 (also known as extracellular signal-regulated kinase [ERK]1/2) or MLCK. Inhibition of MLCK with ML-7 also results in effects that mimic those of post-ovulatory aging: fertilized ML-7-treated eggs show both impaired fertilization and increased extents of polyspermy, and ML-7-treated young eggs have several membrane abnormalities that are shared by post-ovulatory aged eggs. These studies were done with mouse oocytes, and it remains to be fully determined how these findings from mouse oocytes would compare to other species. For studies using methods not amenable to analysis of large sample sizes and data are limited to what images one can capture (e.g., scanning electron microscopy), data should be interpreted conservatively. These data provide insights into causes of reproductive failures at later post-copulatory times. Not applicable. This project was supported by R01 HD037696 and R01 HD045671 from the NIH to JPE. Cortical tension studies were supported by R01 GM66817 to DNR. The authors declare there are no financial conflicts of interest.//////////////////
Expression regulated by
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Ovarian localization
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Molecular Cloning and Functional Analysis of MRLC2 Differential Expressed in MeishanxYorkshire F1 Crossbreeds and Their Parents, Meishan Pigs. Xie HT et al. In order to detect the molecular basis of heterosis in pigs, suppression subtractive hybridization was carried out to investigate the difference in gene expression in the Longissimus dorsi muscle tissues between MeishanxYorkshire F1 crossbreeds and their parents, Meishan pigs. The swine myosin regulatory light chain 2 (MRLC2) gene differentially expressed between the crossbreeds and the purebreds was isolated and identified using semi-quantitative reverse transcriptase polymerase chain reaction and its complete cDNA sequence was obtained using the rapid amplification of cDNA ends method. The nucleotide sequence of the gene is not homologous to any of the known porcine genes. The sequence prediction analysis reveals that the open reading frame of this gene encodes a protein of 172 amino acids containing the putative conserved domain of the EF-hand superfamily. This predicted amino acid sequence of porcine MRLC2 protein exhibits 99%, 98%, 98%, 98% and 97% identity with that of cattle, human, dog, rat and mouse, respectively. The homology analysis revealed that the MRLC2 protein was very much conserved in evolution. The tissue expression analysis indicated that the swine MRLC2 gene is highly expressed in muscle, fat, heart, liver, spleen, lung, kidney, stomach, small intestine, ovary and testis, but not expressed in pancreas.