HANGZHOU - Chinese scientists have made a discovery that could help women who suffer from infertility.

Scientists have discovered that cullin-ring finger ligse-4 (CRL4) complex, a protein complex, is crucial in maintaining female fertility. For the first time its molecular mechanism can be revealed.

A paper on CRL4 complex and how it works was published in US-based Science Magazine on Friday Beijing time.

Fan Hengyu, research group leader from Zhejiang University, said the discovery has revealed how CRL4 complex works in sustaining fertility and postponing the menopause. This can increase the length of the reproductive period.

A baby girl has 100,000 follicles at birth, which are dormant. From the age puberty parts of the follicles begin to grow every month and mature into eggs that are released during ovulation each month, Fan explained.

"During the course of her lifetime, a woman will ovulate only around 300 to 400 mature eggs, and the end of ovulation means the beginning of the menopause," said Fan.

For those with Premature Ovarian Insufficiency (POI), characterized by entering the menopause early before the age of 40, getting pregnant remains a dream as there is no treatment.

Specific oocyte genes are essential for follicles and female fertility, the paper said, but the mechanism that regulates the gene expression was poorly understood.

In a laboratory experiment, the scientists deleted the CRL4 complex from a mouse through gene knockout techniques. Showing no abnormality, the mouse was later diagnosed to be infertile. It had symptoms of rapid oocyte loss, POI and fewer fertility maintaining genes.

Further research has revealed how the CRL4 complex works.

"It activates proteins that are involved in fertility to help regulate the expression of genes, and make sure gene reprogramming for fertility is correct," according to Yu Chao, the paper's first author.

According to Yu, a woman will enter the menopause earlier without the existence of CRL4 complex, but this may not be the only reason.

Science Magazine has said it is a groundbreaking discovery, as it illustrates the importance of CRL4 complex and provides a possible answer to the cause of infertility.

Fan Hengyu said further studies will be done on females lacking the CRL4 complex.

Through intervening the gene expression women can avoid POI and delay the menopause, which will be a direction for future research, Fan said.

"It offers hope, especially at a time when the country has lifted the ban on having a second baby," Fan added.