Researchers at Tel Aviv University identified a new genetic risk factor for the complex eye disease AMD (Age-related Macular Degeneration), a leading cause for loss of eyesight at an advanced age. For the first time, the researchers identified proteins that play a key role in the development and functioning of the tissue affected by the disease, found their exact sites in the genome, and discovered the connection between variations in these genomic regions and the risk for AMD. The researchers: “The new discovery enhances our understanding of the previously unknown function of genomic regions outside the genes. The method we applied may enable the deciphering of additional genetic mechanisms involved in various complex genetic diseases.”

“Comparative studies have identified whole genomic regions that are probably related to the disease but were unable to pinpoint any specific feature in these regions and define it as a risk factor. Our study addressed this problem.” Prof. Ran Elkon

Decoding Mechanisms of a Complex Disease

The study was led by Prof. Ruth Ashery-Padan and Prof. Ran Elkon and their research teams, Mazal Cohen Gulkar, Naama Mesika, Ahuvit David, and May Eshel, from the Department of Human Molecular Genetics and Biochemistry at the Sackler Faculty of Medicine and the Sagol School of Neuroscience at Tel Aviv University. The paper was published in PLOS Biology.

Prof. Ashery-Padan explains that “one of the greater challenges in genetic research today is decoding the genetic mechanisms of complex diseases caused by a combination of several different genetic and environmental factors (rather than an identifiable defect in a single gene). Diabetes, bowel diseases, and various mental illnesses are just a few examples. In our study we chose to focus on AMD, which causes degeneration of the central retina – a major cause of loss of vision at an advanced age in developed countries.”

Prof. Elkon adds: “AMD has a significant genetic component. Studies comparing the genomes of people with and without AMD (as well as a range of other complex genetic diseases) have found differences in several genomic regions, probably associated with risk factors for the disease. However, these differences were not detected in any specific gene, but rather in the extensive regions that stretch between the genes, whose functions and modes of operation are still largely unknown. In fact, comparative studies have identified whole genomic regions that are probably related to the disease but were unable to pinpoint any specific feature in these regions and define it as a risk factor. Our study addressed this problem.”

The study focused on the cells of a layer of tissue called retinal pigmented epithelium (RPE), which supports photoreceptors in the retina, and is essential for their initial development as well as their survival throughout an individual’s lifetime. According to the researchers, this tissue is affected right from the earliest stages of AMD.

Prof. Ruth Ashery-Padan

“Our findings provide new insight into a previously unsolved issue: the functions and mode of operation of genomic sequences located outside the genes, and how they are involved in complex genetic diseases.” Prof. Ruth Ashery-Padan

Novel Research Methodology

“First, we wanted to understand the genetic mechanism that activates and regulates the specific activity of pigmented epithelium cells,” says Prof. Ashery-Padan. “Through a series of experiments, knocking down different proteins in both a mouse model and human cells, we identified two key proteins, LHX2 and OTX2, which together dictate the expression of many genes unique to this tissue. The proteins act as transcriptional activators – binding to specific regulatory sites in the genome to determine which genes will be expressed in a particular cell.”

The next challenge was mapping the precise locations of the two proteins in the genome. The researchers used the innovative technology ChIP-seq – a DNA sequencing method that identifies binding sites where proteins bind to the DNA.

“We found that the binding sites of the two proteins were quite close to each other,” explains Prof. Elkon. “Moreover, these same sites had previously been identified as related to risk factors for AMD (namely, sequences that showed differences between people with and without AMD). We assume that due to changes in DNA sequences in these genomic regions, transcriptional proteins cannot easily find and bind with their binding sites. This reduces the expression of the nearby gene regulated by the transcriptional proteins, which encodes an ion channel known as important to eye function. The decrease in the gene’s activity affects the entire tissue, increasing the risk for development of AMD.”

Prof. Ashery-Padan sums up the study: “In our study we identified two proteins related to risk factors for the complex genetic eye disease AMD. In addition, for the first time, we were able to map the exact genomic sites of these proteins and found that they operate in a region previously identified as related to risk factors for AMD. Our findings provide new insight into a previously unsolved issue: the functions and mode of operation of genomic sequences located outside the genes, and how they are involved in complex genetic diseases. We believe that our novel research methodology will enable the identification and mapping of many other genetic mechanisms related to AMD and other complex genetic diseases.”

A new study examined the pain perception among people with autism and found that they experience pain at a higher intensity than the general population and are less adaptable to the sensation. This finding is contrary to the prevalent belief that people with autism are supposedly ‘indifferent to pain’. The researchers expressed the hope that the findings of their study will lead to more appropriate treatment on the part of medical staff, caregivers, and parents toward people with autism, who do not always express the experience of pain in the usual way.

The study was funded by the Israel Science Foundation and was led by four researchers: Dr. Tami Bar-Shalita of the Sackler Faculty of Medicine at Tel Aviv University who initiated the study, Dr. Yelena Granovsky of the Technion and Rambam Medical Center, and Prof. Irit Weissman-Fogel and Prof. Eynat Gal of the University of Haifa. This study constitutes a framework for the theses of PhD students Tzeela Hofmann and Mary Klingel-Levy, and three articles based on it have already been published or approved for publishing. The present study has been published in the prestigious PAIN journal.

“We know that self-harm could stem from attempts to suppress pain, and it could be that [people with autism] hurt themselves to activate, unconsciously, a physical mechanism of ‘pain inhibits pain’.” Dr. Tami Bar-Shalita

Self-harm Not Proof of Indifference to Pain

“Approximately 10% of the general population suffer from sensory modulation dysfunction, which means sensory hypersensitivity at a level that compromises normal daily functioning and quality of life. These people have difficulty, for example, ignoring or adapting to buzzing or flickering of fluorescent lights, humming of air conditioners or fans, or the crunching of popcorn by someone sitting next to them in the cinema,” explains Dr. Bar-Shalita.

“In previous studies in the lab we found that these people suffer from pain more than those without sensory modulation dysfunction. Since it is known that sensory modulation dysfunction occurs in   people with autism at a rate of 70-90%, it constitutes a criterion for diagnosing autism, and is associated with its severity. We were interested in exploring pain perception in autism, so we asked: do people with autism hurt more than the general population? This question was hardly studied in the lab before we got started.”

According to the researchers, for many years the prevalent opinion was that ‘people with autism hurt less’ or that they were ‘indifferent to pain’. Actually, ‘indifference to pain’ is one of the characteristics presented in the current diagnostic criteria of autism.

The proof of this was, supposedly, their tendency to inflict pain on themselves by self-harm. 

Dr. Bar-Shalita: “this assumption is not necessarily true. We know that self-harm could stem from attempts to suppress pain, and it could be that they hurt themselves to activate, unconsciously, a physical mechanism of ‘pain inhibits pain’.”

“The results of our study indicate that in most cases, the sensitivity to pain of people with autism is higher than that of most of the population, while at the same time they are unsuccessful at effectively suppressing painful stimuli.” Dr. Tami Bar-Shalita

Dr. Tami Bar-Shalita

Contributing to Advancement of Personalized Treatment

This study is a laboratory pain study approved by the ethics committee of the academic institutions and Rambam Medical Center. The study included 52 adults with high-functioning autism (HFA) and normal intelligence – hitherto the largest reported sample in the world in studies on pain among people with autism. The study made use of psychophysical tests to evaluate pain, commonly used in the area of pain study. These methods examine the link between stimulus and response, while the researcher, using a computer, controls the duration and intensity of stimulus and the examinee is asked to rank the intensity of the pain felt by him on a scale of 0 to 100.

The findings have proven beyond doubt that people with autism hurt more. Furthermore, their pain suppression mechanism is less effective.

The researchers conducted a variety of measurements, aimed among other things at examining whether the hypersensitivity to pain derives from a sensitized nervous system or from suppression of mechanisms that are supposed to enable adjustment and, over time, reduce the response to the stimulus. They found that in the case of people with autism, it is a combination of the two: an increase of the pain signal along with a less effective pain inhibition mechanism.

Dr. Bar-Shalita concludes: “our study constituted a comprehensive, in-depth study of the intensity of pain experienced by people with autism. The prevalent belief was that they are supposedly ‘indifferent to pain’, and there are reports that medical and other professional staff treated them accordingly. The results of our study indicate that in most cases, the sensitivity to pain of people with autism is higher than that of most of the population, while at the same time they are unsuccessful at effectively suppressing painful stimuli. We hope that our findings will benefit the professionals and practitioners handling this population and contribute to the advancement of personalized treatment.”

In additional articles soon to be published, the researchers have examined the brain activity of people with autism during pain stimuli, and sub-groups within this population concerning their perception of pain.