The overall focus of the Bianchi laboratory is on developing safer techniques of prenatal diagnosis and new approaches to fetal treatment with a particular interest in fetal aspects of Down syndrome.
Non-Invasive Prenatal Testing (NIPT) of Fetal Genetic Conditions
Currently, prenatal screening for fetal chromosome abnormalities is performed by a combination of an ultrasound examination and measurement of proteins produced by the fetus or placenta that circulate in the mother’s blood. All screen positive women are then offered an invasive procedure, such as amniocentesis or chorionic villus sampling (CVS), to obtain definitive information about fetal chromosome abnormalities. This approach misses 8-10% of cases of Down syndrome and results in 5% of all tests being called “positive.” This means that some pregnant women have unnecessary procedures that could cause a risk of miscarriage.
The Bianchi laboratory is studying various aspects of this evolution in prenatal care. NIPT is already available clinically with a doctor’s order. It detects 99% of cases of Down syndrome, with 0.1% false positive results. This blood test involves the isolation of the cell-free DNA that floats in the mother’s plasma, and uses state-of-the-art genome sequencing to measure if there is an excess or deficiency in the amount of DNA in the fetal genome from a particular chromosome. The major advantage of NIPT is that because it is a more precise screen, far fewer women need to have invasive procedures. The Bianchi laboratory is addressing many of the questions that have been raised since the implementation of this testing into prenatal care. These questions include an analysis of the underlying biological reasons for discrepancy between the NIPT and traditional karyotype results.
Prenatal Treatment of Down Syndrome
The Bianchi laboratory has performed preliminary studies comparing gene expression in fetuses with and without Down syndrome (Slonim et al, 2009 ). Our results showed that the fetuses with Down syndrome experience significant oxidative stress even as early as the second trimester of pregnancy. We hypothesize that by giving safe and effective medication to the pregnant woman carrying a fetus with Down syndrome we will counteract the oxidative stress, which will result in improved brain growth, nerve development, and brain wiring at a critical time in development.
With preliminary funding from the Russo Foundation, the National Institutes of Child Health and Human Development, and Verinata Health, Inc., we have developed a list of candidate drugs to test on human cells and in a mouse model of Down syndrome. As part of this research we are performing a number of behavioral studies before and after treatment on young mice that have 65 genes in common with people who have Down syndrome.
Our long-term goal is to identify several safe and effective FDA-approved small molecules that can be further tested in a human clinical intervention trial of pregnant women carrying fetuses with Down syndrome (Guedj and Bianchi, 2013 ). Because there are currently no available treatments to address the developmental delays experienced by infants with Down syndrome, the proposed work has the potential to revolutionize prenatal management of women carrying affected fetuses. This research is highly significant because even a minor improvement in brain growth and development will advance independent living skills, thereby creating substantial benefits for affected individuals and their families.
Analysis of the Fetal Genome
Prenatal ultrasound examinations detect fetal structural abnormalities but do not provide information about fetal functional development. The Bianchi laboratory is particularly interested in using the messenger (m)RNA in amniotic fluid supernatant as a source of information about the growing human fetus (Hui and Bianchi, 2010 ). We have developed a database of normal and abnormal fetal gene expression in the second and third trimesters of pregnancy. We have also shown that there are distinctly different gene expression profiles in fetuses with specific genetic and non-genetic conditions such as Turner syndrome, twin-to-twin transfusion syndrome, and with exposure to maternal obesity.
We hypothesize that by using bioinformatics to compare normal to abnormal gene expression we can identify novel diagnostic and treatment targets that can result in inexpensive, noninvasive, point of care, multiplex real-time quantitative polymerase chain reaction amplification assays that could determine fetal or neonatal well-being from a functional (rather than an anatomic) perspective.
Figure 1. Multiplex-reverse transcriptase PCR amplification of cell-free RNA obtained from 10 pregnant women in the third trimester. Each colored line within the box represents a different blood sample. The genes amplified represent fetal sequences that we have previously shown to circulate within the mother (Maron et al, 2007 ). CAMP= cyclic adenosine monophosphate; NRL=neural retina leucine zipper; S100B=S100 calcium binding protein β; NRP1=neuropilin 1; ROBO4=roundabout homolog 4.