Proceedings of The Physiological Society
Durham University (2010) Proc Physiol Soc 21, C16 and PC16
Heritability of mechanosensory traits in humans
H. Frenzel1, J. Bohlender2, K. Pinsker2, M. Gross2, G. R. Lewin1
1. Department of Neuroscience, Max-Delbr?ck-Center for Molecular Medicine (MDC) Berlin-Buch, Berlin, Germany. 2. Clinic for Audiology and Phoniatrics, Charit? - Universit?tsmedizin Berlin, Berlin, Germany.
The aim of this study was to explore the genetics of different sensory traits in humans with a focus on traits that rely on the transduction of mechanical stimuli. In a classical twin study, the heritability of the different traits was determined. One hundred twin pairs participated in the study, of which 66 were monozygotic and 34 were dizygotic. Heritability values were estimated by structural equation modeling (1). Two aspects of touch sensitivity were investigated, the vibration detection threshold and tactile acuity. For vibration detection threshold determination, a sinusoidal 125 Hz vibration was applied proximal to the nail of the little finger and the detection threshold determined as an amplitude. For the vibration detection threshold a very robust heritability value of 0.52 (0.33 - 0.67, 95 % confidence interval (CI)) was estimated. In the tactile acuity test, the ability to detect the orientation of gratings of different spacing with the fingertip of the little and index fingers was assessed and a threshold in mm determined. The estimated heritability value was 0.27 (0.05 - 0.46 95 % CI). This is the first report about a genetic contribution to the variation of touch sensitivity in humans. Three parameters of hearing were investigated, the pure tone threshold in decibel (dB) and the strength as well as the reproducibility of the otoacoustic emissions, the latter two being measures of outer hair cell function. The heritability estimates for all three measures were very high at 0.80 (0.67 - 0.87, 95 % CI), 0.76 (0.62 - 0.85, 95 % CI) and 0.88 (0.80 - 0.93, 95 % CI), respectively. A third mechanosensory system was tested, the vascular baroreflex, a system that senses and balances short term changes in blood pressure. Baroreflex slope, a measure of the strength of reflex reactions showed a heritability value of 0.39 (0.17 - 0.57, 95 % CI) and estimated heritability of baroreflex sequence frequency, which is the number of baroreflex reactions in a certain period of time at rest, was 0.56 (0.34 - 0.71, 95 % CI). We found significant correlation between some of these mechanosensory traits on a phenotypic level, e.g. between tactile acuity and pure tone thresholds (r = 0.16; p < 0.05, t-test). One of the investigated systems does not require transduction of mechanical stimuli, the cutaneous thermosensory system. We could determine values for the heritability of cold and warmth detection thresholds, 0.40 (0.16 - 0.60, 95 % CI) and 0.37 (0.14 - 0.56, 95 % CI), respectively. In contrast, we did not find a significant heritability of heat and cold-pain thresholds. These results show that most of the investigated traits and all of the mechanosensory traits show significant heritability. Genetic influences on these traits are thus assessable by routinely used medical testing equipment. We demonstrated the usability of the employed tests for use in genome-wide approaches.
Where applicable, experiments conform with Society ethical requirements