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July 28, 2017
Digest

Children’s Visual Engagement Is Heritable, Altered in Autism

Reduced attention to other people’s eyes and faces is a behavior
Reduced attention to other people’s eyes and faces is a behavior associated with autism. In an NIH-funded study, researchers explored the potential genetic foundation of this behavior, which can appear by the first 6 months of age.

How children visually engage with others in social situations is a heritable behavior that is altered in children with autism, according to a study funded by NIH. The study appeared in Nature. Autism spectrum disorder affects how a person acts, communicates and learns. In the United States, approximately 1 out of 68 children has the disorder.

Reduced attention to other people’s eyes and faces is a behavior associated with autism; it is often used to screen for and help diagnose the disorder. In the current study, researchers from Washington University in St. Louis and Emory University explored the potential genetic foundation of this behavior, which can appear by the first 6 months of age and persist as children grow older.

“Research shows that autism likely has a genetic basis. Siblings of children diagnosed with autism and people with certain genetic mutations have a higher risk of developing the disorder, compared to the general population,” said Dr. Diana Bianchi, director of NICHD, which provided funding for the study along with NIMH. “Understanding how genes influence social behaviors will help researchers identify new or better ways to treat autism.”

The study team conducted eye-tracking experiments in a group of 250 typically developing toddlers ages 18 to 24 months, including 82 identical twins (41 pairs), 84 non-identical twins (42 pairs) and 84 non-sibling children (42 randomized pairs). They also evaluated 88 non-twin children diagnosed with autism.

Each child watched videos that showed either an actress speaking directly to the viewer or scenes of children interacting in daycare. In all video frames, children could look at the onscreen characters’ eyes, mouth, body or surrounding objects.

Special software captured how often the children looked at different regions, as well as the timing and direction of eye movements.

The team found that identical twins had synchronized visual patterns, compared to non-identical twins and non-sibling pairs.

Identical twins tended to shift their eyes at the same times and in the same direction. They also were more likely to look at the subject’s eyes or mouth at the same moments.

“By comparing identical twins who share the same genes to non-identical twins and randomly paired children who do not share the same genes, the study is one of the first to show that social visual behaviors are under genetic control,” said Dr. Lisa Gilotty, chief of NIMH’s Research Program on Autism Spectrum Disorders.

To explore this concept further, the researchers evaluated children with autism and discovered that they looked at eye and mouth regions—the most heritable visual traits—much less, compared to the other groups of children.

HIV Hijacks Surface Molecule to Invade Cell

Researchers at NIH have discovered a key step in the process that HIV uses to inject its genetic material into cells. Working with cultures of cells and tissues, the researchers prevented the invasion process by chemically blocking this step, preventing HIV genetic material from entering cells. The findings could lead to the eventual development of new drugs to prevent HIV infection.

The study, appearing in Cell Host & Microbe, was led by Dr. Leonid Chernomordik at NICHD.

To infect a cell, a protein on the surface of HIV binds to molecules on the cell’s surface. This binding process initiates a sequence of events that ends with HIV’s outer membrane fusing with the cell’s membrane. The virus’ genetic material then passes into the cell. The researchers discovered that the binding process activates a protein, called TMEM 16F, that transfers another molecule inside the cell membrane, phosphatidylserine, to the membrane’s outer surface. They believe molecules in the viral membrane bind with the exposed phosphatidylserine on the cell surface to enhance the virus’ fusion to the cell.

The researchers found that blocking the transfer of phosphatidylserine to the cell surface—or attaching another molecule to phosphatidylserine so it can’t bind with HIV—prevents the virus from infecting the cell. Theoretically, developing drugs that could block each of these steps could provide the basis for treatments to prevent HIV from infecting cells, but much more research is needed.

Eye Microbiome Trains Immune Cells to Fend Off Pathogens in Mice

Bugs in your eyes may be a good thing. Resident microbes living on the eye are essential for immune responses that protect the eye from infection, new research shows. The study, which appeared in the journal Immunity on June 27, demonstrates the existence of a resident ocular microbiome that trains the developing immune system to fend off pathogens. The research was conducted at NEI.

“This is the first evidence that a bacterium lives on the ocular surface long-term,” said Dr. Rachel Caspi, senior investigator in NEI’s Laboratory of Immunology. “This work addresses a longstanding question about whether there is a resident ocular microbiome.”

For years, the ocular surface was thought to be sterile because of the presence of an enzyme called lysozyme that destroys bacteria, antimicrobial peptides and other factors that rid the eye of microbes that may land from the air (or from our fingers) onto the surface of the eye.

Dr. Anthony St. Leger, research fellow in Caspi’s laboratory, was able to culture bacteria from the mouse conjunctiva, the membrane that lines the eyelids. He found several species of Staphylococci, which are commonly found on the skin, and Corynebacterium mastitidis (C. mast). But it wasn’t clear whether those microbes had just arrived on the eye and were en route to being destroyed or whether they lived on the eye for extended periods of time.

The researchers found that C. mast, when cultured with immune cells from the conjunctiva, induced the production of interleukin (IL)-17, a signaling protein critical for host defense. Upon further investigation, they found that IL-17 was produced by gamma delta T cells, a type of immune cell found in mucosal tissues. IL-17 attracted other immune cells called neutrophils—the most abundant type of white blood cell—to the conjunctiva and induced the release of anti-microbial proteins into the tears. The researchers are currently investigating the unique features that can make C. mast resistant to the immune response that it itself provokes and allow it to persist in the eye.

The researchers are also investigating whether other bacteria play a role in regulating eye immunity.

“We’ve established the proof of concept of a central ocular microbiome,” St. Leger said. “It’s well known that there are good bacteria in the gut that modulate the immune response. Now we show that this relationship exists in the eye. That’s important for how we think about treating ocular disease.”

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