Usher syndrome (USH) represents the most prevalent form of inherited recessive deafness associated with blindness. In the inner ear, USH proteins constitute the components of stereocilia bundle and mechanoelectricaltransduction(MET)machinery.WehavepreviouslyidentifiedtheCIB2geneencoding Calcium and Integrin-Binding protein 2 (CIB2) as the cause of USH1 and non-syndromic deafness in diverse populations (Patel et al 2015, Riazuddin et al 2012, Seco et al 2016). CIB2 is expressed in the haircellstereociliainrodents,butitsexactfunctionwasunknown(Riazuddinetal2012).Intheprevious fundingperiod,wegeneratedamousemodelcarryingthehumandeafness-relatedCib2variant(Cib2F91S knock-in) and characterized it together with a mouse line lacking CIB2 (Cib2tm1a). We found that both thesemousestrainsaredeafandhavenoconventionalMETresponsesintheauditoryhaircells,despite thepresenceoftiplinksthatnormallygatetheMETchannelsandapparentlyunchangedlocalizationof mutantCIB2inthestereociliaofCib2F91S/F91Smice.WealsofoundthatCIB2bindstothecomponentsof thehaircellMETcomplex,TMC1andTMC2,andtheseinteractionsaredisruptedbydeafness-causing Cib2 variants. We concluded that CIB2 is essential for the MET function (Giese et al 2017). This novel elementoftheMETmachineryisparticularlyinterestingbecauseitmayberesponsibleforatleastsome ofthemultiplewell-knowneffectsofCa2+onthehaircellmechanotransduction.Here,wewillexplorethe exactroleofCIB2inMET.Towardsthisend,wehavealreadygeneratedanotherknock-inmousestrain (Cib2R186W).R186WvariantdoesnotaffectCIB2interactionwithTMC1/2butimpairsitscalciumbuffering ability. Cib2R186W mice will be compared with Cib2F91S allele that impairs CIB2 interaction with TMC1/2, leadingtothelossofMET.OurstudiesalsoestablishedthatCIB2deficiencyresultsinabnormalgrowth ofthetransducingshorterrowstereociliainthehairbundlewithoutaffectingnon-transducingtallestrow stereocilia (Giese et al 2017). Thus, CIB2 may represent an important molecule, linking MET channel activityandstereociliaactincoreremodeling.Theexistenceofsuchlinkwasestablishedinourparallel study(Velez-Ortegaetal2017).Here,wewilldeterminehowCIB2controlstheheightofthetransducing stereociliaintheauditoryhaircells.Finally,wehavealsofoundthatCIB2deficiencyresultsindecreased numberoftheinnerhaircell(IHC)synapses.Therefore,wewillinvestigatethepotentialmechanismsof CIB2 involvement in the IHC synaptic function. The expected outcomes of this study are to uncover (a) the precise mechanism of deafness associated with CIB2 deficiency and (b) the physiological role of CIB2 protein in hair cell functions, especially in MET and neurotransmission. The potential for positive impactisinherent;?decipheringthefunctionsofUSHproteinsisacriticalsteptowardsthedevelopmentof actualtherapiesforthetreatmentand/orpreventionofthisdebilitating,lifelongdisease.

Public Health Relevance

. Advancement in the understanding of molecular mechanisms of the inner ear is a prerequisitetodevelopingtherapeuticstrategiesforhearingimpairment.Thestudiesoutlinedinthisproposal seek to understand the general function of a calcium binding protein known as CIB2 and its associated pathophysiology due to mutations of CIB2 encoding this protein. Thus the proposed research is developing fundamentalknowledgethatwillhelptoreducetheburdenofhumanhearingloss.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
2R01DC012564-07
Application #
9473538
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Watson, Bracie
Project Start
2012-12-01
Project End
2022-11-30
Budget Start
2017-12-01
Budget End
2018-11-30
Support Year
7
Fiscal Year
2018
Total Cost
Indirect Cost
Name
University of Maryland Baltimore
Department
Otolaryngology
Type
Schools of Medicine
DUNS #
188435911
City
Baltimore
State
MD
Country
United States
Zip Code
21201
Giese, Arnaud P J; Tang, Yi-Quan; Sinha, Ghanshyam P et al. (2017) CIB2 interacts with TMC1 and TMC2 and is essential for mechanotransduction in auditory hair cells. Nat Commun 8:43
Dev Borman, Arundhati; Rachitskaya, Aleksandra; Suzani, Martina et al. (2017) Benign Yellow Dot Maculopathy: A New Macular Phenotype. Ophthalmology 124:1004-1013
Rehman, Atteeq U; Bird, Jonathan E; Faridi, Rabia et al. (2016) Mutational Spectrum of MYO15A and the Molecular Mechanisms of DFNB3 Human Deafness. Hum Mutat 37:991-1003
Fong, Keith S K; Hufnagel, Robert B; Khadka, Vedbar S et al. (2016) A mutation in the tuft mouse disrupts TET1 activity and alters the expression of genes that are crucial for neural tube closure. Dis Model Mech 9:585-96
Hufnagel, Robert B; Zimmerman, Sarah L; Krueger, Laura A et al. (2016) A new frontonasal dysplasia syndrome associated with deletion of the SIX2 gene. Am J Med Genet A 170A:487-91
Seco, Celia Zazo; Giese, Arnaud P; Shafique, Sobia et al. (2016) Novel and recurrent CIB2 variants, associated with nonsyndromic deafness, do not affect calcium buffering and localization in hair cells. Eur J Hum Genet 24:542-9
Waryah, A M; Shahzad, M; Shaikh, H et al. (2016) A novel CHST3 allele associated with spondyloepiphyseal dysplasia and hearing loss in Pakistani kindred. Clin Genet 90:90-5
Simon, Mariella; Richard, Elodie M; Wang, Xinjian et al. (2015) Mutations of human NARS2, encoding the mitochondrial asparaginyl-tRNA synthetase, cause nonsyndromic deafness and Leigh syndrome. PLoS Genet 11:e1005097
Rehman, Atteeq U; Santos-Cortez, Regie Lyn P; Drummond, Meghan C et al. (2015) Challenges and solutions for gene identification in the presence of familial locus heterogeneity. Eur J Hum Genet 23:1207-15
Mašindová, Ivica; Šoltýsová, Andrea; Varga, Lukáš et al. (2015) MARVELD2 (DFNB49) mutations in the hearing impaired Central European Roma population--prevalence, clinical impact and the common origin. PLoS One 10:e0124232

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