In a study of 50 pairs of fraternal twins with hearing loss, the scientists uncovered evidence linking the hearing loss to a particular region of DNA that previously was tied to a hereditary form of progressive deafness that begins much earlier in life.

The work is believed to be the first genomic screening in search of genes associated with hearing loss using a sample of elderly people drawn from the general population. The 50 sets of twins were drawn from a group of twins who are veterans of World War II and the Korean War.

The results suggest "that this region may contain an important locus for hearing loss in the general population," said Terry E. Reed, Ph.D., professor of medical and molecular genetics at the IU School of Medicine.

The region of DNA identified by the IU study, a section of chromosome 3 named DFNA18, was implicated in a 2001 study of hereditary deafness in a large German family. It's possible the two studies are pointing to the same gene or genes, with variation in the genes resulting in differences in susceptibility to hearing loss, Dr. Reed said.

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In his dissertation work, Jonas Nilsson looked for a naturally occurring retardant mechanism for ErbB receptors. He worked on a banana fruit fly protein, Kekkon-1, which serves to slow down the fly ™s equivalent of the ErbB receptor. A similar protein was cloned for humans and then described and named leucin-rich and immunoglobulin-like protein 1 (LRIG1). The findings showed that LRIG1 belongs to a protein family of its own, with three family members, LRIG1, LRIG2 and LRIG3. Studies of LRIG1 showed that it binds to ErbB receptors and accelerates their degradation, thus slowing down their activity. LRIG2 and LRIG3 evince great similarities to LRIG1, which indicates that they may perform similar functions in the cell, but this has not yet been demonstrated. However, studies of brain tumors showed that the expression of LRIG proteins is associated with improved survival rates in patients. Further, it was shown that the expression of LRIG3 is an independent prognostic marker in malignant brain tumors.

In summary, by way of analogies to the banana fruit fly protein Kekkon-1, Jonas Nilsson ™s dissertation identifies a new family of genes, confirms his theories that it functions as a retardant of the tumor protein ErbB1, and finally shows that the expression of LRIG proteins is associated with increased survival in patients with malignant brain tumors.

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