Medical Research: What is the background for this study? What are the main findings?
Dr. Forster: As a result of our paternity testing work at the Institute for Forensic Genetics in Munster (Germany), we have accumulated a pool of over 24,000
parents and their children, of whom we know for certain that they are
biologically related. Occasionally we observe a new mutation in these
children, which must have come either from the sperm or the egg of one
of the parents. As we analyse highly variable microsatellite DNA (a
repetitive type of DNA, also know as STR DNA, which stands for “short
tandem repeat” DNA), we can fairly easily find out whether the mutation
has come from the mother or the father. It turns out that the fathers
contribute 6-7 times more mutations to the children than the mothers do.
This has long been known. What is new is that we have observed that the
male and female teenagers at puberty do NOT set out with the same low
mutation load, but instead, the teenage boys already have a sixfold
higher mutation load in their sperm than the girls in their oocytes.
Medical Research: What should clinicians and patients take away from your report?
Dr. Forster: In recent years clinical research has accumulated showing that children
from older fathers (above 35) but also from teenage fathers have an
increased risk for conceiving children with birth defects. The incidence
for birth defects in the general population is 1.5 percent, and the
increased rate for teenage fathers might be on the order of 2 percent.
Also, these children seem to be at a higher risk of low birth weight,
low IQ, schizophrenia and autism. It appeared logical to those
researchers that older fathers may have a less than pristine genome in
their germline, which would explain the higher incidence of defects. But
they were puzzled by the teenage effect, and suggested that other
explanations need to be sought. Our study removes this complication by
showing that teenage fathers already set off with a high DNA mutation
Medical Research: What recommendations do you have for future research as a result of this study?
Dr. Forster: So our main message is to clinical researchers to continue looking for
genetic explanations for birth defects and cognitive disorders in
children of teenagers, especially where the father is young. As the
individual risk of an abnormal child is still relatively low, expectant
teenage couples should not be too anxious. But as a policy matter, even
half a percent of additional cases of birth defects in a population is
worrying and teenage parenthood should therefore continue to be
discouraged. I caution however I say this as a geneticist, and ideally
the epidemiologists should now embark on quantitative risk assessments
which can be implemented as guidelines.
Peter Forster, Carsten Hohoff, Bettina Dunkelmann, Marianne Schürenkamp, Heidi Pfeiffer, Franz Neuhuber, Bernd Brinkmann. Elevated germline mutation rate in teenage fathers. Proceedings of the Royal Society B, February 2015 DOI: 10.1098/rspb.2014.2898
MedicalResearch.com Interview with:, & Dr. Peter Forster PhD (2015). High DNA Mutation Rate In Teenage Dads May Lead To More Birth Defects MedicalResearch.com