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Twin Studies

THE INDIANA UNIVERSITY TWIN PANEL

In 1967, Dr. Joe C. Christian began collecting data from twins for a study dealing with plasma lipids. 
Twins are considered special by researchers because they provide built-in controls for genetic and environmental factors.  The Indiana University (IU) Twin Panel grew to contain over  3,000 pairs of twins who have participated in one or more studies dealing with a variety of research topics.

Participating twins did so on a voluntary basis.  They  consented in writing to the procedures of each
particular study.  The procedures in studies often consist of a family history, different tests, and physical
measurements.  We only  did zygosity testing for new twins who participate or are eligible for an ongoing study.   Most recent studies have involved pairs already in the panel and we are not  recruiting new twins

The following is a brief summary of a few of the studies that were conducted with the aid of the IU Twin Panel.

Cardiovascular Disease Risk Factors: Plasma cholesterol levels were studied in newborn pairs of identical (monozygous, MZ) and fraternal (dizygous, DZ) twins and in the children of MZ twins.  Cholesterol levels for MZ twins are more alike than are the cholesterol levels for DZ twins. Differences in cholesterol levels appear at birth as well as later in life.  The effects that the mother has on the child before birth were found to be important in determining plasma cholesterol levels, which is an important risk factor in coronary heart disease.  In addition to cholesterol, the twin panel has participated in various studies of blood pressure, another important cardiovascular disease factor.

Osteoporosis:  Studies of bone density have utilized twins in the panel.  One major early finding was that the density of bone is genetically determined, but the rate of bone loss with age is not genetic.  The results had implications for ways to reduce the risk of osteoporosis and the resulting risk of age-related fractures.  Some of our DZ twins have participated in ongoing studies of sibling-pairs attempting to find
genes related to bone metabolism.

Dermatoglyphics:  We have collected a large series of hand, finger, and foot prints on twins and their families for the purposes of studying human development.  When prints are formed, they appear to be influenced by environmental factors as well as by multiple genetic effects.  Some of the patterns in the prints of MZ twins do seem to vary depending on twin placental type even though, as a group, MZ twins have more similar prints than do DZ twins.  De-identified prints from approximately 1,500 sets of twins and other multiple births (and in some instances other family members) are stored in the American Dermatoglyphics Association archives at the Smithsonian Institute in Washington D.C. 

Psychological Development:  Broad ranges of psychological studies have involved the twin panel.  One such study observed the genetic and environmental effects of fears. Researchers found that we are genetically prepared to acquire fears of certain situations.  However, as children, we learn patterns of emotional responsiveness from observations of our parents but develop fears of specific situations through interaction with our peers.

More recent studies have focused primarily on adult twins. We completed a 30-year longitudinal study of cardiovascular disease risk factors in male twins born from 1917-1927. The most recent examinations focused on brain structure as measured by magnetic resonance imaging (MRI).  We continue to collaborate with a group at SRI International who are following this cohort’s mortality. A study of pairs of twins from this group who survived into their 70s without major health problems located chromosome regions associated with healthy aging.  In this same sample, a study of DZ pairs who both had age-related hearing loss identified a locus  near a previously  reported  rare single gene form of hereditary deafness.  DNA samples from 343 twin pairs in the latter study are stored and under the control of the Twins Committee of the Medical Follow-Up Agency (MFUA) in the National Academy of Sciences in Washington D.C.

More information about the Indiana University Twin Panel is available by contacting:

Dr. Terry E. Reed
Indiana University School of Medicine
Department of Medical and Molecular Genetics
410 West 10th Street, HS 4015
Indianapolis, Indiana 46202- 3002

Telephone (317) 274-5739
E-mail treed@iupui.edu