WDR1 presence in the songbird basilar papilla

Abstract

WD40 repeat 1 protein (WDR1) was first reported in the acoustically injured chicken inner ear, and bioinformatics revealed that WDR1 has numerous WD40 repeats, important for protein-protein interactions. It has significant homology to actin interacting protein 1 (Aip1) in several lower species such as yeast, roundworm, fruitfly and frog. Several studies have shown that Aip1 binds cofilin/actin depolymerizing factor, and that these interactions are pivotal for actin disassembly via actin filament severing and actin monomer capping. However, the role of WDR1 in auditory function has yet to be determined. WDR1 is typically restricted to hair cells of the normal avian basilar papilla, but is redistributed towards supporting cells after acoustic overstimulation, suggesting that WDR1 may be involved in inner ear response to noise stress. One aim of the present study was to resolve the question as to whether stress factors, other than intense sound, could induce changes in WDR1 presence in the affected avian inner ear. Several techniques were used to assess WDR1 presence in the inner ears of songbird strains, including Belgian Waterslager (BW) canary, an avian strain with degenerative hearing loss thought to have a genetic basis. Reverse transcription, followed by polymerase chain reactions with WDR1-specific primers, confirmed WDR1 presence in the basilar papillae of adult BW, non-BW canaries, and zebra finches. Confocal microscopy examinations, following immunocytochemistry with anti-WDR1 antibody, localized WDR1 to the hair cell cytoplasm along the avian sensory epithelium. In addition, little, if any, staining by anti-WDR1 antibody was observed among supporting cells in the chicken or songbird ear. The present observations confirm and extend the early findings of WDR1 localization in hair cells, but not in supporting cells, in the normal avian basilar papilla. However, unlike supporting cells in the acoustically damaged chicken basilar papilla, the inner ear of the BW canary showed little, if any, WDR1 up-regulation in supporting cells. This may be due to the fact that the BW canary already has established hearing loss and/or to the possibility that the mechanism(s) involved in BW hearing loss may not be related to WDR1.

WDR1 expression in normal and noise‐damaged Sprague‐Dawley rat cochleae

“…The findings that WDR1 is overexpressed and colocalized with cofilin/ADF after acoustic overstimulation suggest that WDR1 may play a role either in restoring cytoskeletal integrity in supporting cells or in a cell signaling pathway required for regeneration (Adler et al, 1999; Lomax et al, 2001; Oh et al, 2002). Our most recent work on the inner ear of the Belgian Waterslager (BW) canary, an avian strain with degenerative hearing loss thought to have a genetic basis, has demonstrated WDR1 expression in HCs, but not in supporting cells (Adler et al, 2008). However, upregulation of such expression remains to be seen, due to the fact that the BW canary has already established hearing loss and/or to the possibility that the mechanism involved in BW hearing loss may not be related to WDR1 (Adler et al, 2008).…”

“…This antibody has been shown to label avian auditory HCs, homogene cells, and cuboidal cells (Adler et al, 1999; Oh et al, 2002). The specificity of the WDR1 antibody in avian cochlea has been demonstrated by disappearance of the WDR1 bands on western blotting after preincubation with blocking peptide (Adler et al, 2008). In the mammalian cochlea, however, the specificity of the WDR1 antibody has yet to be tested.…”

“…Other inner ear structures such as the tectorial membrane (Cotanche, 1987b), the dark cells of the tegmentum vasculosum (Ryals et al, 1995), and the nerve fibers underlying the auditory epithelium (Ofsie and Cotanche, 1996; Wang and Raphael, 1996) show evidence of structural repair. Consequently, birds are able to regain most of their lost hearing as well as the structure of the inner ear itself (McFadden and Saunders, 1989; Cotanche, 1999; Dooling et al, 2006; Adler et al, 2008).…”

“…As mentioned above, the expression of WDR1 is increased in the avian auditory HC region in birds after acoustic overstimulation, whereas the majority of other genes are either downregulated or unaffected (Gong et al, 1996; Adler et al, 1999; Lomax et al, 2001). Besides, WDR1 has drawn attention because of its potential relationship with cofilin/actin depolymerizing factor (ADF), an important component in the highly regulated process of actin polymerization and depolymerization, has been suggested (Adler et al, 2008). Our previous work has elucidated the colocalization of WDR1 with actin and cofilin in HCs in the avian auditory epithelium (Oh et al, 2002).…”

Autoantibody against WD repeat domain 1 is a novel serological biomarker for screening of thyroid neoplasia

“…Rabbit polyclonal AWA was produced by Dr. Hiroshi Abe and kindly provided for us. Because significant sequence identity in numerous species was demonstrated in WDR1, the full‐length clone of Xenopus WDR1 was selected for immunizing rabbits.…”