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Similar phenotypes caused by mutations in OTOG and OTOGL
Anne M M Oonk1, Joop M Leijendeckers, Patrick L M Huygen
11Department of Otorhinolaryngology, Hearing & Genes, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; 2Radboud University Nijmegen Medical Centre, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands; 3Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; 4Programa de Medicina Molecular i Genètica, Hospital Vall d'Hebron, Barcelona, Spain; 5Unitat de Genètica, Universitat Pompeu Fabra, Barcelona, Spain; 6Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain; 7Unidad de Genética Molecular, Hospital Universitario Ramón y Cajal, IRYCIS, Madrid, Spain; 8John P. Hussman Institute for Human Genomics, University of Miami, Miami, Florida, USA; 9Dr. John T. Macdonald Department of Human Genetics, University of Miami, Miami, Florida, USA; 10Division of Pediatric Genetics, Ankara University School of Medicine, Ankara, Turkey; and 11Department of Human Genetics, Radboud University Nijmegen Medical Centre, The Netherlands.
Objectives:
Recently, OTOG and OTOGL were identified as human deafness genes. Currently, only four families are known to have autosomal recessive hearing loss based on mutations in these genes. Because the two genes code for proteins (otogelin and otogelin-like) that are strikingly similar in structure and localization in the inner ear, this study is focused on characterizing and comparing the hearing loss caused by mutations in these genes.
Design:
To evaluate this type of hearing, an extensive set of audiometric and vestibular examinations was performed in the 13 patients from four families.
Results:
All families show a flat to downsloping configuration of the audiogram with mild to moderate sensorineural hearing loss. Speech recognition scores remain good (>90%). Hearing loss is not significantly different in the four families and the psychophysical test results also do not differ among the families. Vestibular examinations show evidence for vestibular hyporeflexia.
Conclusion:
Because otogelin and otogelin-like are localized in the tectorial membrane, one could expect a cochlear conductive hearing loss, as was previously shown in DFNA13 (COL11A2) and DFNA8/12 (TECTA) patients. Results of psychophysical examinations, however, do not support this. Furthermore, the authors conclude that there are no phenotypic differences between hearing loss based on mutations in OTOG or OTOGL. This phenotype description will facilitate counseling of hearing loss caused by defects in either of these two genes.
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