Disease relevance of DFNB31

• Mutations in the DFNB31 gene encoding the PDZ scaffold protein whirlin are causative for hearing loss in man and mouse [1].

High impact information on DFNB31

• BAC-mediated transgene correction of the mouse phenotype and mutation analysis identified the causative gene as encoding a novel PDZ protein called whirlin [2].
• Whirlin is known to be essential for the elongation process of the stereocilia of sensory hair cells in the inner ear, though its complete spatial and temporal expression patterns remained elusive [1].
• These findings indicate that whirlin is part of a macromolecular PDZ protein scaffold that functions in the organization of the pre- and/or postsynaptic side of photoreceptor and hair cell synapses [1].
• The results of immunocytochemical staining and electron microscopy revealed that CIP98 is localized both in dendrites and axons [3].
• Interestingly, CIP98 interacts with CASK (calmodulin-dependent serine kinase), a member of the membrane-associated guanylate kinase (MAGUK) family that plays important roles in the molecular organization of proteins at synapses [3].

Biological context of DFNB31

• The whirler (wi) mouse mutant, characterised by deafness and circling behaviour, maps to the corresponding region on the murine chromosome 4, thus suggesting that DFNB31 and whirler may result from orthologous gene defects [4].
• A genetic linkage with polymorphic markers surrounding D9S1776 was detected, thereby identifying a novel deafness locus, DFNB31 [4].
• Mutation screening of DFNB31/WHRNrevealed four nonpathogenic sequence variants and a novel frameshift mutation [c.2423delG] + [c.2423delG] that changed the reading frame and induced a novel stop codon at amino acid 818 ([p.Gly808AspfsX11] + [p.Gly808AspfsX11]) [5].
• In view of its direct association with CASK, CIP98 may be involved in the formation of CASK scaffolding proteins complex to facilitate synaptic transmission in the CNS [3].

Anatomical context of DFNB31

• In the present study, we isolated CIP98, a novel protein (98 kDa) consisting of three PDZ domains and a proline-rich region, which is widely expressed in the central nervous system [3].
• In situ hybridization and immunohistochemical staining patterns demonstrate that CIP98 is expressed strongly in certain types of neurons, i.e. pyramidal cells in layers III-V of the cerebral cortex, projecting neurons in the thalamus and interneurons in the cerebellum [3].

Other interactions of DFNB31

• DFNB31, a recessive form of sensorineural hearing loss, maps to chromosome 9q32-34 [4].
• GRCAH domain identified in this study was conserved among mammalian GRID2IP orthologs and mammalian CIP98/KIAA1526 orthologs [6].

References