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01.05.2012 23:00

Gene mutation leads to the loss of two senses: touch and hearing

Barbara Bachtler Press office
Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch

Those who hear well can also feel well. But those who hear poorly also have a poorer sense of touch. How this is connected, now Dr. Henning Frenzel and Prof. Gary R. Lewin from the Max Delbrück Center (MDC) Berlin-Buch discovered that both senses have a common genetic basis. In patients with Usher syndrome, a hereditary form of hearing impairment with visual impairment, they discovered a gene mutation that is also the cause of the affected person's poor sense of touch. The investigation was preceded by various studies, including one with unidentifiable and dizygotic healthy twins (PloS Biology, doi: 10.1371 / journal.pbio.1001318). In total, the researchers examined 518 volunteers.

Those who hear well can also feel well. But those who hear poorly also have a poorer sense of touch. How this is connected, now Dr. Henning Frenzel and Prof. Gary R. Lewin from the Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch discovered. They were able to show that both senses have a common genetic basis. In patients with Usher syndrome, a hereditary form of hearing impairment with visual impairment, they discovered a gene mutation that is also the cause of the affected person's poor sense of touch. The investigation was preceded by various studies, including one with unidentifiable and dizygotic healthy twins (PloS Biology, doi: 10.1371 / journal.pbio.1001318) *. In total, the researchers examined 518 volunteers.

Hearing and touch are two different sensory systems in all vertebrates and therefore also in humans. In both cases, however, mechanical stimuli are converted into electrical signals. When hearing, the sound waves trigger vibrations that bend the hair cells in the inner ear, which convert the mechanical stimulus into electrical signals. They enter the brain via the auditory nerve. Something similar happens when you touch it: the mechanical stimulus - sliding your fingers over a rough or smooth surface, perceiving vibrations - is picked up by sensors in the skin, converted into an electrical stimulus and passed on to the brain.

100 pairs of twins examined
In recent years, around 70 genes have been identified in humans that cause hearing loss (deafness) when they are mutated. "Strangely enough, no genes that influence the sense of touch have yet been found," said Prof. Lewin. To see whether there is also an inheritable component in the sense of touch, the researchers first examined 100 pairs of twins - 66 pairs of identical twins and 34 pairs of dizygotic twins. Identical twins are genetically identical; dizygoti twins have a 50 percent genetic match. The tests showed that more than 50 percent of the subjects' different tactile abilities are determined by genes. The hearing and touch tests also showed that there is a connection between the sense of hearing and touch.

The researchers therefore suspected that genes that influence the sense of hearing may also have an influence on the sense of touch. In the next step they therefore went to a school for the hearing impaired in Berlin. There they examined the tactile ability of 39 adolescents who were hard of hearing from birth. They compared the findings obtained with the data from their twin study and found that not all hearing-impaired adolescents had a poor sense of touch. "But in a noticeably large number of these young people, the sense of touch was only weakly developed," explains Prof. Lewin.

Since the effort would have been too great to find out in the young hearing impaired which of the around 70 genes that impair the sense of hearing may also worsen the sense of touch, the researchers examined patients with Usher syndrome in a further step. This is an inherited form of hearing loss in which patients become additionally blind over time. The disease, in which the patients have various degrees of hearing impairment, has been genetically researched very well. Nine genes play a role here, the mutations of which trigger the disease.

In a special consultation at Charité - Universitätsmedizin, the researchers examined patients with Usher syndrome from all over Germany as well as patients at the La Fe University Clinic in Valencia, Spain, who were recorded in a gene file. The research showed that not all patients with Usher syndrome have a poor sense of touch. The researchers were able to show that only the patients with Usher syndrome who have a mutation in the USH2A gene have a less sensitive sense of touch. This mutation is also responsible for the hearing loss in these 19 patients. The 29 Usher syndrome patients in whom this mutation could not be detected can feel normally. The researchers thus provided evidence that there is a common genetic basis for the senses of hearing and touch. They suspect that even more genes will be discovered in the future that influence these two senses at the same time.

Women hear better and are more sensitive than men
And the researchers found another interesting detail in their five-year study. "If women complain that their husbands do not hear them properly, then there is indeed something to it," says Prof. Lewin. "The studies with a total of 518 people, including 295 women, have actually shown that women hear better and are more sensitive than men."

* A genetic basis for mechanosensory traits in humans
Henning Frenzel1, Jörg Bohlender2, Katrin Pinsker2, Bärbel Wohlleben2, Jens Tank3, Stefan G. Lechner1, Daniela Schiska2, Teresa Jaijo5, Franz Rueschendorf4, Kathrin Saar4, Jens Jordan3, José M. Millán5 and Manfred Gross2, Gary R. Lewin1,6

1 Department of Neuroscience, Max Delbrück Center for Molecular Medicine, Robert-Rössle-Str. 10, Berlin-Buch D-13092 Germany, 2Department of Audiology and Phoniatrics, Charité, Universitätsmedizin, Berlin, Augustenburger Platz 1, Berlin D-13353 Germany. 3Institute of Clinical Pharmacology, Hannover Medical School, Carl-Neuberg-Str. 1, Hannover D-30625, Germany, 4 Experimental genetics of cardiovascular disease, Max Delbrück Center for Molecular Medicine, Robert-Rössle-Str. 10, Berlin-Buch D-13092 Germany, 5Genetics Unit, Hospital Universitario La Fe, Avda. de Campanar, 21, 46009 and CIBERER, Valencia, Spain
6 Author for Correspondence

Contact:
Barbara Bachtler
Press office
Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch
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e-mail: [email protected]
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Additional Information:

http://www.nature.com/neuro/journal/v15/n1/pdf/nn.2985.pdf


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