Women who experience severe gestational hypertension may give birth to boys at lower risk for testicular cancer, although the exact reasons why are still unclear, according to a paper published in the November 1, 2008, issue of Cancer Research, a journal of the American Association for Cancer Research.

Andreas Pettersson, M.D., a doctoral student at Karolinska Institute in Sweden, said the protective effect of gestational hypertension may be due to the hormones that are released when a placenta malfunctions.

“Ironically, a malfunctioning placenta may lower the risk,” said Pettersson.  “One possible reason is that estrogens are lower in pregnancies that develop severe gestational hypertension or preeclampsia, and this lack of estrogens may lower the risk of testicular cancer.”

Pettersson and colleagues observed 293 cases of germ-cell testicular cancer in the Swedish Cancer Register and 861 controls in the Swedish Medical Birth Register.  They extracted data on maternal and pregnancy characteristics such as gestational hypertension, proteinuria, anemia and glucoseuria.

If women experienced severe gestational hypertension, their male offspring were 71 percent less likely to develop testicular cancer than those women who experienced no hypertension.  If the gestational hypertension was mild, there was a 62 percent increased risk of testicular cancer.

Beyond decreased estrogen, severe gestational hypertension and preeclampsia increases the level of human Chorionic Gonadotropin, another pregnancy-related hormone, which may also have a protective effect against testicular cancer.

Pettersson said that these findings add knowledge to the mechanisms behind testicular cancer, but he cautioned against reverse thinking.

“This study does not suggest that a woman who does not have gestational hypertension is going to give birth to a boy who is at increased risk for testicular cancer,” said Pettersson.

Scientists at the Gladstone Institute of Cardiovascular Disease (GICD) and the University of California San Francisco (UCSF) have identified a genetic factor critical to the formation of chambers in the developing heart. The discovery of the role of a microRNA called miR-138, could offer strategies for the treatment of congenital heart defects.The heart is one of the first and most important organs to develop. In fact, embryos cannot survive long with a functioning heart. In vertebrates (animals with backbones), special cells form a heart tube; that tube loops back on itself to form the atrium and ventricle and the canal and valve that separates them. This requires a complicated sequence of genes turning on and off. MicroRNAs are very small RNAs of 20 to 25 nucleotides that regulate numerous gene functions. Approximately 650 human miRNAs are known, but only a few have yet been studied to determine what they actually do in a cell.

Researchers, led by Sarah Morton, an MD/PhD student at UCSF and GICD Director Deepak Srivastava MD, examined zebrafish, which are an ideal model system for understanding genetic functions. Zebrafish are small, reproduce fast, and are essentially transparent so that that events of heart formation can be studied while they are still alive. Yet many of their systems are quite similar to those of humans. For example, miR-138 is exactly the same in zebrafish and humans.

“What’s interesting is that a single microRNA is responsible for setting up the distinct patterning of a developing heart into separate chambers,” said Dr. Srivastava, senior author of the study. “Since many congenital heart defects involve abnormalities in the formation of the chambers, this is important information in finding ways of treating or avoiding those defects.”

The GICD scientists reported in today’s issue of the Proceedings of the National Academy of Sciences USA, that miR-138 is present in the zebrafish heart at specific times and in specific places in the developing heart. Furthermore, they showed that it is required to insure that the cardiac chambers develop properly. When the scientists used genetic engineering techniques to eliminate miR-138, cardiac function was disrupted, and the ventricles did not develop correctly, with the muscle precursor cells failing to mature properly.

“The miR-138 function was required during a discrete developmental window that occurred 24-34 hours after fertilization,” said Sarah Morton. The team also showed that the miRNA controlled development by regulating numerous factors that function jointly to define the chambers, including a key enzyme that makes retinoic acid.

Clubfoot, one of the most common birth defects, has long been thought to have a genetic component.  Now, researchers at Washington University School of Medicine in St. Louis report they have found the first gene linked to clubfoot in humans.

Their research will be published in the Nov. 7 issue of the American Journal of Human Genetics.

By studying a multi-generation family with clubfoot, the scientists traced the condition to a mutation in a gene critical for early development of lower limbs called PITX1.  While other genes are also likely to be linked to clubfoot, the new finding is a first step toward improved genetic counseling and the development of novel therapies.

“To our knowledge this report is the first evidence for PITX1 mutation in human disease,” said Christina Gurnett, M.D., Ph.D., assistant professor of neurology, of pediatrics and of orthopedic surgery at the School of Medicine.  “Once we identified the mutation, we proved that all of the individuals in this family with lower extremity malformations also have the mutation.  Having large families to work with is very helpful in genetic research.”

Gurnett and her colleagues analyzed the DNA of 35 extended family members of an infant male patient of Matthew Dobbs, M.D., associate professor of orthopedic surgery at the School of Medicine and a clubfoot specialist at St. Louis Children’s Hospital and St. Louis Shriners Hospital.  The patient, the most severely affected in the family, had clubfoot in both feet, duplicated first toes and was missing the tibia in the right leg.

Gurnett and Dobbs visited the family members in their community to examine their lower limbs and to take DNA samples.  They found that 13 family members were affected: Five additional family members had clubfoot, which was more severe in the right foot in three of them.  Five others had lower limb abnormalities including flatfoot, an underdeveloped patella and hip dysplasia.

Through the genome-wide study, Gurnett and her colleagues found a region on chromosome 5 that was common to all family members affected.  From there, they identified a mutation in a gene critical for early development of lower limbs called PITX1.  The PITX1 mutation was found in all affected family members and in three carriers who showed no clinical symptoms.

Dobbs, senior author of the study, said the finding is an exciting step in developing a better understanding of the genetic basis of clubfoot, which affects about 1 in 1,000 new births.

“Clubfoot is a complex disorder meaning that more than one gene as well as environmental factors will be discovered to play a role in its etiology,” Dobbs said.  “Identifying the genes for clubfoot will allow for improved genetic counseling and may potentially lead to new and improved treatment and preventive strategies for this disorder.”

Dobbs treats children with clubfoot and other orthopedic abnormalities using the Ponseti method, a treatment that involves weekly casting and the manipulation of clubfoot soon after birth.  In 2007, Dobbs developed a new dynamic brace called the Dobbs brace for clubfoot that allows active movement, preservation of muscle strength in the foot and ankle and fewer restrictions on the child than the traditional brace.

About 80 percent of clubfoot cases are idiopathic, meaning the cause is unknown and the patient has no other birth defects.  A familial link plays a role in about 25 percent of cases.  The condition occurs in males twice as often as in females and occurs more often in the right foot.  About half of the cases affect both feet, including the bones, muscles, tendons and blood vessels.  If untreated, those affected walk on the outside of their feet, which can lead to long-term pain and disability.

Gurnett said some clinical characteristics of the family members with the PITX1 mutation suggest that the genetic defect may be linked to idiopathic clubfoot.  First, the majority of the affected family members had clubfoot, but no other abnormalities.  Second, there were five females who carried the gene but did not have clubfoot, which supports the lower incidence of clubfoot in females.  Third, clubfoot affects the right foot more frequently, a hallmark of mutations in PITX1.

Previous studies had shown a relation between PITX1 and the development of hindlimbs in other vertebrates.  In mice, a loss of PITX1 leads to shorter femur length and fewer digits on the right foot than on the left.  An alteration of the gene in a developing chick wing changes it so that it looks more like a leg.  In vertebrates such as the manatee and stickleback fish, an alteration has resulted in evolutionary changes in the development of the pelvis.

“It’s our job to prove that this is going to be important for many kids with clubfoot,” Gurnett said.  “Until now, we didn’t know whether clubfoot was a muscle, nerve, spinal cord or brain problem.  Now, we have an idea that clubfoot may result from mutations of genes that are involved in early limb development.”

Gurnett said she and her colleagues will take the finding back to the lab to look for other factors involved in the pathway or how environmental effects may influence the gene.  She and Dobbs, who have been studying the genetics of clubfoot for a decade, plan to investigate the frequency of PITX1 gene mutations in other families with clubfoot.

Scientists have identified about two dozen genes that control embryonic stem cell fate.  The genes may either prod or restrain stem cells from drifting into a kind of limbo, they suspect.  The limbo lies between the embryonic stage and fully differentiated, or specialized, cells, such as bone, muscle or fat.

By knowing the genes and proteins that control a cell’s progress toward the differentiated form, researchers may be able to accelerate the process – a potential boon for the use of stem cells in therapy or the study of some degenerative diseases, the scientists say.

Their finding comes from the first large-scale search for genes crucial to embryonic stem cells.  The research was carried out by a team at the University of California, San Francisco and is reported in a paper in the July 11, 2008 issue of “Cell.”

“The genes we identified are necessary for embryonic stem cells to maintain a memory of who they are,” says Barbara Panning, PhD, associate professor of biochemistry and biophysics at UCSF, and senior author on the paper.  “Without them the cell doesn’t know whether it should remain a stem cell or differentiate into a specialized cell.”

The scientists used a powerful technique known as RNA interference, or RNAi, to screen more than 1,000 genes for their role in mouse embryonic stem cells.  The technique allows researchers to “knock down” individual genes, reducing their abundance in order to determine the gene’s normal role.

The research focused on proteins that help package DNA.  In the nucleus, DNA normally wraps around protein complexes called nucleosomes, forming a structure known as chromatin.  This is what makes up chromosomes.

They found 22 proteins, each of which is essential for embryonic stem cells to maintain their consistent shape, growth properties, and pattern of gene expression.

Most of the genes code for multi-protein complexes that physically rearrange, or “remodel” nucleosomes, changing the likelihood that the underlying genes will be expressed to make proteins.

The main player they identified is a 17-protein complex called Tip60-p400.  This complex is necessary for the cellular memory that maintains embryonic stem cell identity, Panning explains.  Without it, the embryonic stem cells turned into a different cell type, which had some features of a stem cell but many features of a differentiated cell.

The scientists believe that Tip60-p400 is necessary for embryonic stem cells to correctly read the signals that determine cell type.  These findings are not only important for understanding cellular memory in embryonic stem cells, but will also likely be relevant to other cell types, they say.

Inactivation of other genes disrupted embryonic stem cell proliferation.  These genes were already known to have only slight influence on viability of mature cells in the body.  This suggests that embryonic stem cells are “uniquely sensitive to certain perturbations of chromatin structure,” the scientists report.

If other types of stem cells are also found to be sensitive to these chromatin perturbations, this could lead to novel cancer therapies in the future, Panning says.

Prenatal biochemical screening tests are widely used to look for chromosomal abnormalities in the fetus which can lead to serious handicap, or even death during gestation or in the first few days after birth. But these tests are only able to detect fewer than half of the total chromosomal abnormalities in the fetus, a scientist will tell the annual conference of the European Society of Human Genetics tomorrow (Monday 2 June) Dr. Francesca R. Grati, of the TOMA Laboratory, Busto Arsizio, Italy, says that these findings mean that women should be better informed on the limitations of such diagnostic tests.The researchers studied 115,576 prenatal diagnoses carried out during the last fourteen years. 84,847 were amniocenteses, usually carried out around the 16th week of pregnancy, and 30,729 chorionic villus samplings, which can be undertaken from 12 weeks into the pregnancy. Both these tests carry an increased risk of miscarriage, so the decision on whether or not to undertake them can be difficult to weigh up. “Since our sample included a large number of women aged less than 35 who underwent invasive prenatal diagnosis without any pathological indication to do so, we felt that the results could be useful in helping to inform pre-test counselling of such women”, says Dr. Grati. “Up until now, the information we had came from smaller studies which only looked at the performance of these tests in detecting a limited number of chromosomal abnormalities.”

After analysing the results of the chromosomal abnormalities from their own dataset, the researchers combined them with the official detection rates for these abnormalities published by SURUSS and FASTER consortia. These are multi-centre research groups involved in the investigation of screening and diagnostic tests performed in pregnancy, whose results are being used to optimise prenatal care for pregnant patients. They found that current screening procedures were only able to detect half the total chromosomal abnormalities in women both younger and older than 35.

The TOMA laboratory is particularly suited to carry out this kind of research, says Dr. Grati, because it was among the first in the world to deal with prenatal diagnosis, and has a vast number of prenatal diagnostic samples at its disposal.

Current tests do not detect all fetal chromosomal abnormalities, but only trisomies 21 (Down syndrome), 18 (Edward’s syndrome), and 13 (Patau syndrome), monosomy X (Turner syndrome), and triploids (conceptuses with 69 chromosomes instead of 46). “These are common vital chromosomal abnormalities, but there are many others which are not picked up by these tests”, says Dr. Grati. “And the tests do not even detect 100% of the common abnormalities.”

At conception, 23 chromosomes from each parent combine to create a fetus with 46 chromosomes in all its cells. Trisomy occurs when the fetus has one additional chromosome (47 instead 46). The extra genetic material from the additional chromosome causes a range of problems of varying severity.

In Down syndrome, for example, where the fetus has three copies of chromosome 21, babies are usually born with impaired cognitive ability and physical growth, cardiac defects and a characteristic facial appearance. Unlike many other such abnormalities, however, babies born with Down syndrome are able to lead relatively normal lives and their life expectancy is around 50 years.

Other than trisomy, the fetus can also have the loss of genetic material (deletions) or chromosomal abnormalities in a non-homogeneous form, where there is a mixture of two cell lines, one normal and the other abnormal. “Some of these disorders are relatively common in the fetus, which may have as much chance of surviving as children who are born with Down syndrome, and it is worrying that current biochemical tests are not always able to detect them” says Dr. Grati. “Our research confirms that it is fundamental for doctors to counsel patients about the limitations of current screening methods, so that they can make an informed decision on whether or not to undergo invasive diagnostic testing.”