Contact: Will Sansom
Phone: (210) 567-2579
E-mail: sansom@uthscsa.edu

A marmaset father carries its baby on its back.
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San Antonio (March 28, 2007) – Marmosets, small monkeys that live in the forests of Central and South America, are usually born as twins. Their early development is quite interesting. Through the exchange of embryonic stem cells in the womb, they become genetic “chimeras,” which means they carry genes of their brother or sister in their own tissues.

A new study suggests this gene-mixing arrangement has a strong effect on the nurturing behavior of marmoset fathers. “We found that fathers cared more for infants that had skin chimerism as opposed to those that didn’t, whereas mothers were the opposite and cared more for those that were not chimeric,” said Corinna Ross, Ph.D., of The University of Texas Health Science Center at San Antonio’s Sam and Ann Barshop Institute for Longevity and Aging Studies.

A postdoctoral fellow at the Barshop Institute in the laboratory of renowned comparative biologist Steven Austad, Ph.D., Dr. Ross conducted the research for her doctoral dissertation at the University of Nebraska. Her mentors and co-authors were Guillermo Orti, Ph.D., and Jeffrey French, Ph.D.

“We aren’t sure if the moms are rejecting chimeric infants or if the dads are more attracted,” Dr. Ross said. “Our hypothesis is that this may be an adaptation to induce the fathers to care more.”

Marmosets weigh about a pound (the size of a rat) and their maximum life span is 15 years. Dr. Ross and colleagues studied Wied’s black tufted-ear marmoset. The animals’ diminutive size makes them suitable to rear in colonies, and because their life span is shorter than larger primates, research conclusions may be reached sooner.

The Barshop Institute is establishing a marmoset animal model program in aging under the direction of Suzette Tardif, Ph.D., assistant professor of cellular and structural biology in the Health Science Center’s Graduate School of Biomedical Sciences. Dr. Ross is shifting her research focus to aging as a fellow at the Barshop Institute.

Interestingly, recent studies elsewhere have shown humans have a higher rate of chimerism than previously believed, Dr. Ross said. The Discovery Channel recently released a program titled “I am my own twin,” which documents human cases of chimerism. Recent research has also described a phenomenon known as microchimerism, which occurs when fetal stem cells cross the placenta to the mother. It is unknown where these stem cells may reside in the mother.

It’s of course not possible to draw conclusions about human fathers from the marmoset study, Dr. Ross said.

“What this study does do is change our view of marmosets and our view of their individualism,” she said. “If all tissues have the animals’ own DNA and their siblings’ DNA, how do we define those animals as individuals?”

The National Science Foundation funded the study.


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