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Mosaic Loss of Chromosome X in Older Women Influenced by Inherited Factors

, by Jennifer K. Loukissas, M.P.P.

cartoon showing mosaic loss of X in women as they age

 As some women age, their white blood cells can lose a copy of chromosome X. A new study sheds light on the potential causes and consequences of this phenomenon.

Credit: Created by Linda Wang with

NCI featured the latest research on the loss of one copy of a woman's two X chromosomes, a phenomenon known as mosaic loss of chromosome X (mLOX), in a Media Advisory. The study identified 56 common genetic variants that influenced whether mLOX developed. mLOX is associated with several health conditions, including cancer. The analysis was performed using blood collected from over 800,000 women.

The research study was co-led by Mitchell Machiela, Sc.D., M.P.H., senior investigator in the Integrative Tumor Epidemiology Branch and appeared June 12, 2024, in Nature. Other current and former DCEG investigators who participated in the study include Drs. Weiyin Zhou, Derek Brown, Kai Yu, Ph.D., Wen-Yi Huang, Ph.D., M.S.P.H., Dr. Neal Freedman, and Stephen J. Chanock, M.D

Dr. Machiela was awarded scientific tenure from the NIH last week. He leads DCEG's investigations into genetic mosaicism.

Read the NCI Media Advisory on


Liu A et al. Population analyses of mosaic X chromosome loss identify genetic drivers and widespread signatures of cellular selectionNature. 2024.