Usherin expression is highly conserved in mouse and human tissues

Usher syndrome is an autosomal recessive disease that results in varying degrees of hearing loss and retinitis pigmentosa. Three types of Usher syndrome (I, II, and III) have been identified clinically with Usher type II being the most common of the three types. Usher type II has been localized to three different chromosomes 1q41, 3p, and 5q, corresponding to Usher type 2A, 2B, and 2C respectively. Usherin is a basement membrane protein encoded by the USH2A gene. Expression of usherin has been localized in the basement membrane of several tissues, however it is not ubiquitous. Immunohistochemistry detected usherin in the following human tissues: retina, cochlea, small and large intestine, pancreas, bladder, prostate, esophagus, trachea, thymus, salivary glands, placenta, ovary, fallopian tube, uterus, and testis. Usherin was absent in many other tissues such as heart, lung, liver, kidney, and brain. This distribution is consistent with the usherin distribution seen in the mouse. Conservation of usherin is also seen at the nucleotide and amino acid level when comparing the mouse and human gene sequences. Evolutionary conservation of usherin expression at the molecular level and in tissues unaffected by Usher 2a supports the important structural and functional role this protein plays in the human. In addition, we believe that these results could lead to a diagnostic procedure for the detection of Usher syndrome and those who carry an USH2A mutation.