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Mouse reveals genetic cause for glue ear in children

Scientists have found the first evidence of a genetic cause for the childhood disease otitis media (OM). Also known as glue ear, OM is the most common cause of hearing impairment and surgery in children in the developed world. In the past, genetic studies of human families have shown that a genetic component predisposes children to recurrent OM, but the gene responsible had not been identified.

Now, a mouse model with hearing loss known as Junbo, bred at the Medical Research Council Mammalian Genetics Unit, has allowed scientists to identify one of the rogue genes involved. It has also shed light on how this gene encourages OM. A mouse model is a breed of mouse used by scientists to study the effect and progress of a human disease.

In a paper published today in Public Library of Science Genetics, the researchers describe how the Junbo mouse shares the symptoms of OM experienced by many children. Junbo develops the disease soon after birth and it quickly grows into a more severe form known as chronic suppurative OM. Many children experience an acute form of the disease that causes ear infection and fever. However, a significant number of children will go on to develop a recurrent or a chronic form of the disease often with no overt infection and accompanied by an effusion, a thick glue-like fluid. It is this form of the disease that the Junbo mouse mimics.

Director of the Mammalian Genetics Unit, Professor Steven Brown who led the research team explains: ‘‘Studying children with OM and their families has shown scientists that a genetic factor is at work but until now nothing has been known about the underlying genetic pathways that actually cause the disease. The Junbo mouse has allowed us to find the genetic mutation responsible - a change in the gene Evi1.”

The Evi1 gene encodes a transcription factor, a protein that helps to translate DNA into instructions for the body. In Junbo the Evi1 transcription factor is mutated and the products of the Evi1 gene are found in the cells that line the middle ear when there is inflammation.

Professor Brown concludes: Fifty percent of UK children will have had an episode of OM by the age of twelve months and 35% of 12 to 36 month-olds will have repeated bouts and it has been estimated that five million school days are missed every year due to OM. Because the Junbo mouse provides a model of how OM affects children I hope that it will help researchers to figure out new ways to tackle this disease so that children will suffer less from OM and sore ears in the future.”

Journal Link : Mutation at the Evi1 Locus in Junbo Mice Causes Susceptibility to Otitis Media
http://genetics.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pgen.0020149

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