Category Archives: Transhuman News

By Mary Brophy Marcus HealthDay Reporter

THURSDAY, Feb. 27, 2014 (HealthDay News) -- A new DNA study begins to explain why girls are less likely than boys to have an autism spectrum disorder.

It turns out that girls tend not to develop autism when only mild genetic abnormalities exist, the researchers said. But when they are diagnosed with the disorder, they are more likely to have more extreme genetic mutations than boys who show the same symptoms.

"Girls tolerate neurodevelopmental mutations more than boys do. This is really what the study shows," said study author Sebastien Jacquemont, an assistant professor of genetic medicine at the University Hospital of Lausanne, in Switzerland.

"To push a girl over the threshold for autism or any of these neurodevelopmental disorders, it takes more of these mutations," Jacquemont added. "It's about resilience to genetic insult."

The dilemma is that the researchers don't really know why this is so. "It's more of an observation at a molecular level," Jacquemont noted.

In the study, the Swiss researchers collaborated with scientists from the University of Washington School of Medicine to analyze about 16,000 DNA samples and sequencing data sets from people with neurodevelopmental disorders, including autism spectrum disorders.

The investigators also analyzed genetic data from almost 800 families affected by autism for the study, which was released online Feb. 27 in the American Journal of Human Genetics.

The researchers analyzed copy-number variants (CNVs), which are individual variations in the number of copies of a particular gene. They also looked at single-nucleotide variants (SNVs), which are DNA sequence variations affecting a single nucleotide. Nucleotides are the basic building blocks of DNA.

The study found that females diagnosed with any neurodevelopmental disorder, including attention-deficit/hyperactivity disorder and intellectual disability, had more harmful CNVs than males who were diagnosed with the same disorder. Females with autism also had more harmful SNVs than males with the condition.

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Gene Study Offers Clues to Why Autism Strikes More Males

A new technique adds a spatial dimension to studies of gene expression

Neuron pathways from the motor cortex connect multiple regions throughout the mouse brain. Credit: Allen Mouse Brain Connectivity Atlas

Scientists can now take snapshots of where and how thousands of genes are expressed in intact tissue samples, ranging from a slice of a human brain to the embryo of a fly.

The technique, reported today inScience, can turn a microscope slide into a tool for creating data-rich, three-dimensional maps of how cells interact with one another a key to understanding the origins of diseases such as cancer. The methodology also has broader applications, enabling researchers to create, for instance, unique molecular barcodes to trace connections between cells in the brain, a stated goal of the US National Institutes of Health'sHuman Connectome Project.

Previously, molecular biologists had a limited spatial view of gene expression, the process by which a stretch of double-stranded DNA is turned into single-stranded RNAs, which can in turn be translated into protein products. Researchers could either grind up a hunk of tissue and catalogue all the RNAs they found there, or use fluorescent markers to track the expression of up to 30 RNAs inside each cell of a tissue sample. The latest technique maps up to thousands of RNAs.

Mapping the matrix In a proof-of-principle study,molecular biologist George Churchof Harvard Medical School in Boston, Massachusetts, and his colleagues scratched a layer of cultured connective-tissue cells and sequenced the RNA of cells that migrated to the wound during the healing process. Out of 6,880 genes sequenced, the researchers identified 12 that showed changes in gene expression, including eight that were known to be involved in cell migration but had not been studied in wound healing, the researchers say.

This verifies that the technique could be used to do rapidly what has taken scientists years of looking at gene products one by one, says Robert Singer, a molecular cell biologist at Albert Einstein College of Medicine in New York, who was not involved in the study.

The method hinges on fossilizing the RNA in place in the cell and sequencing it. First, the researchers affix a slice of tissue on a surface and wash away the cellular membranes, keeping the cells' scaffolding, RNA and proteins in place. Next, the researchers add chemicals to 'reverse-transcribe' each short segment of RNA, converting it into circular fragments of single-stranded DNA. Then they add more chemicals to make hundreds of copies of each DNA circle, which form clusters called nanoballs. These nanoballs are chemically linked together to form a durable, transparent matrix that approximates the original layout of the cell, and then analyzed by SOLiD sequencing, a method that uses digital imaging to capture the colors and locations of fluorescent probes as they interrogate the DNA.

The technique has applications beyond understanding gene-expression patterns, says Jay Lee, a medical doctor and biologist in Churchs lab. At present, the most advanced technology for labelling and mapping neurons,Brainbow, is limited to 100 simultaneous hues. Lee says that its now possible to create 1 trillion different molecular barcodes from small strands of RNA. He is also working on techniques to add barcodes to proteins inside the cell.

Lee says that the technique reminds him of a scene from the science-fiction filmThe Matrix, in which the character Neo sees the binary source code underlying his environment. This sounds a little corny, he concedes, but he adds, I want biology to be like that.

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Gene Activity Can Now Be Mapped Spatially across Intact Tissue