Female fertility may be affected by a gene that makes a protein called adrenomedullin.

Female mice with only one copy of the gene have “significantly reduced fertility” compared with those with two copies of the gene, say researchers at the University of North Carolina at Chapel Hill.

The researchers included Manyu Li, PhD, and Kathleen Caron, PhD.

They studied female mice with either one or two copies of the gene. The researchers let the mice mate with male mice, which also had either one or two copies of the gene.

Fertility was lower in females with only one copy of the gene, regardless of their mates. The number of these genes in the male mice did not affect fertility, the study shows.

The report appears in today’s online edition of The Journal of Clinical Investigation.

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Key Protein

In previous studies, the researchers showed that having just one copy of the adrenomedullin gene is associated with pregnancy complications in mice.

Adrenomedullin is one of many proteins made by the body; genes hold the recipes for such proteins.

With one adrenomedullin gene instead of two, levels of the protein are lower than normal.

Adrenomedullin performs several jobs in the body. One affects implantation of a fertilized egg into the womb for pregnancy.

Most likely, adrenomedullin promotes blood flow to the implantation site and may have other roles in implantation, write the researchers.

If so, low adrenomedullin levels might hamper implantation. That’s what happened in this study.

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Study’s Limits

This was a study in mice, not people.

Also, the findings don’t mean the adrenomedullin gene is solely responsible for female fertility. Fertility is complex and likely involves many genes.

But the scientists say their studies “raise the intriguing possibility that modest alterations in [adrenomedullin] gene expression in the human population may contribute significantly to overall reproductive health.”

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By Miranda Hitti, reviewed by Louise Chang, MD

SOURCES: Li, M. The Journal of Clinical Investigation, Sept. 14, 2006; online edition. News release, Journal of Clinical Investigation.