Usher syndrome is a widespread disease which can result in deafness and blindness. It is inherited autosomal recessively and belongs to one of about 7000 rare genetic diseases. Certain genes can be linked to one of three subtypes of Usher syndrome. Each form of the Usher syndrome, Usher type 1, Usher type 2 and Usher type 3, triggers a different phenotype. Some forms of blindness occur in cause of DNA mutations. In case of Usher syndrome they can result in retinitis pigmentosa. First, perception of colours worsens, later on, bright dark vision deteriorates. After that, this disease can lead to complete blindness. Deafness manifests in all subtypes at a different time. Whilst with Usher type 1 a complete deafness can be expected already in the first years of life. Usher type 2 and 3 affected individuals show a later manifestation of hearing impairment. In addition, early hearing loss in Usher type 1 could lead to a diminished development of speech. Genetic defects, which end up in a disturbed development of stereocilia can also affect the vestibular organ and leads to vestibular dysfunction or a delay in independent sitting or walking. Nowadays, some forms of therapy are being researched, in some cases there are already possibilities to eradicate the phenotype. However, it requires molecular genetic methods which determine the exact causal mutation in a certain gene. In this thesis, two mutations possibly associated to hearing impairment and vision loss could be found. An already known mutation in the MYO7A gene, NM_000260.4:c.1258A>T, which is already related to the Usher syndrome was identified in all affected individuals of one consanguineous family. Additionally, we were able to detect the variant NM_004525.3:c.11972G>C in the LRP2 gene in all affected individuals from a consanguineous family. Some mutations in this gene are known to cause Donnai-Barrow syndrome or Stickler like syndrome. Further analysis has to be performed, to confirm the relation of this mutation with the present disease.
Molecular genetic analyses of consanguineous families with hearing impairment and vision loss
Brugger, B. A. (Author). 2025
Student thesis