_-_Illustration_-_Andrii_Vodolazhskyi_M1_4bb73c51d46c449285a21e8af28684d6-620x480.jpg "New Protein Discovered That Preserves Egg Chromosome Integrity During Aging")
How OMC1 Protects Chromosome Cohesion in Human Eggs
Researchers have identified a previously unknown protein that preserves chromosome stability in mammalian eggs from the fetal stage through adulthood, according to a study published on October 29, 2026, in Nature Aging. Led by Professor Kei-ichiro Ishiguro from the Graduate School of Medicine at Chiba University in Japan, the research team discovered that a protein named OMC1 acts as a maintenance factor that extends the chromosomal lifespan of oocytes by safeguarding a crucial molecular glue known as REC8 cohesin.
The Role of REC8 Cohesin in Oocyte Aging
Unlike sperm cells, which men produce continuously after hitting puberty, female mammals produce all their eggs during the fetal stage. Once formed, these eggs enter a long dormant state called the dictyate stage, pausing cell division until ovulation occurs. During this extended arrest, a protein complex called REC8 cohesin functions as a molecular glue to hold chromosome copies together. However, REC8 is never replenished during dormancy. As this protein weakens progressively with age, older eggs frequently develop aneuploidy—a condition involving the wrong number of chromosomes that serves as a leading cause of infertility, miscarriage, and chromosomal disorders like Down syndrome. Before this study, scientists debated whether oocytes actively protect this cohesin or simply leave the protein to degrade passively over time.
Discovery of the Omc1 Gene and Protein
By combining these findings with data from mice experiencing delayed meiosis, the researchers pinpointed a previously uncharacterized gene active specifically in oocytes just before they enter dormancy. They named this gene Omc1 and its resulting protein OMC1, standing for Oocyte-specific Meiotic Chromosome protein 1. Further analysis revealed that OMC1 localizes to the chromosomes of the egg alongside REC8 cohesin, remaining present from the fetal stage through adulthood.
Experimental Results in Gene-Modified Mice
To determine how OMC1 functions, the research team engineered mice lacking the Omc1 gene. Once eggs from these knockout mice entered the dormant period, REC8 cohesin began disappearing from chromosomes prematurely. Consequently, even young eggs from these mice exhibited weakened chromosome cohesion and errors in chromosome separation similar to those typically observed in aged eggs. When the researchers restored OMC1 in adult oocytes, REC8 levels on the chromosomes partially recovered, and chromosome errors declined. This recovery indicates that OMC1 actively works to keep REC8 in place rather than halting the aging process entirely. “Based on these results, OMC1 should be regarded not as a factor that stops aging itself, but as a maintenance factor that extends the chromosomal lifespan of eggs,” Professor Ishiguro remarks.
Implications for Human Reproductive Aging
The discovery also sheds light on potential genetic variations affecting human fertility. Previous genetic studies have identified variants in CCDC201, the human counterpart to mouse OMC1, which are linked to early menopause and the loss of ovarian function. When the research team tested a truncated mouse OMC1 protein that corresponds to one of these human variants, the altered protein failed to localize to oocyte chromosomes and could not restore chromosome cohesion. These findings suggest that impaired OMC1 and CCDC201 function directly contributes to individual variations in reproductive aging. As societies experience an increasing average age at childbirth, the research team notes that identifying the mechanisms protecting chromosome cohesion carries significant modern relevance. Within the next decade, these insights may help scientists develop safe approaches to preserve or supplement OMC1 function before cohesin is lost, establishing new strategies to maintain oocyte quality and extend fertility.
Frequently Asked Questions About Oocyte Chromosome Preservation
What causes chromosome errors in older eggs?
Chromosome errors occur because REC8 cohesin—the molecular glue holding chromosome copies together during the long dormant period from the fetal stage until ovulation—is never replenished and weakens progressively with age.
Who led the research team behind the OMC1 discovery?
The study was led by Professor Kei-ichiro Ishiguro from the Graduate School of Medicine at Chiba University in Japan, alongside co-authors including Sakie Iisaka, Dr. Ryuki Shimada, Dr. Tomoya S. Kitajima, and Dr. Shuhei Yoshida.
How does the OMC1 protein protect female eggs?
OMC1 localizes to the chromosomes of the oocyte and actively works to keep REC8 cohesin in place, preventing the protein from disappearing prematurely during dormancy.
What is the human equivalent of the mouse Omc1 gene?
The human counterpart to mouse OMC1 is CCDC201, a gene whose variants have previously been associated with early menopause and the loss of ovarian function in humans.
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