NEW YORK, Sept. 10 - About four percent of expressed genes in cloned mice are abnormal, according to research done at the Whitehead Institute.
Though they are not necessary evident at the phenotypic level via clinical examination, these abnormalities could lead to severe health problems, the researchers report.
"Recent studies showing premature death, pneumonia, liver failure, and obesity in aging cloned mice could be a consequence of these gene-expression abnormalities," the authors write in a paper slated to appear this week in the Proceedings of the National Academies of Science.
Embryonic stem cells used to make whole animals "would likely produce organisms that are abnormal, since many of the abnormally expressed genes have defined roles in fetal development," concluded Rudolf Jaenisch, the study's principal investigator.
Jaenisch and colleagues used Affymetrix gene arrays to screen 10,000 genes for abnormalities in the placentas and livers of cloned mice. The researchers said cloned animals should be examined via molecular tissue analyses as well as clinical examinations.
Participating in the study were researchers from the Whitehead Institute for Biomedical Research, the John A. Burns School of Medicine at the University of Hawaii, the Dana-Farber Cancer Institute, and Harvard Medical School.