HUMAN MUTATION 17:403�411 (2001)

© 2001 WILEY-LISS, INC.

RESEARCH ARTICLE

Pendred Syndrome, DFNB4, and PDS/SLC26A4Identification of Eight Novel Mutations and PossibleGenotype�Phenotype CorrelationsColleen Campbell,1 Robert A. Cucci,1 Sai Prasad,1 Glenn E. Green,2 J. Bradley Edeal,1

Chad E. Galer,1 Lawrence P. Karniski,3–5 Val C. Sheffield,4,6 and Richard J.H. Smith1*1Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, Iowa2Department of Surgery, Arizona Health Services Center, Tucson, Arizona3Department of Internal Medicine, University of Iowa Hospitals and Clinics, Iowa City, Iowa4Department of Pediatrics, University of Iowa Hospitals and Clinics, Iowa City, Iowa5Department of Veteran Affairs Medical Center, Iowa City, Iowa6Howard Hughes Medical Institute, University of Iowa Hospitals and Clinics, Iowa City, Iowa

Communicated by Mark H. Paalman

Mutations in PDS (SLC26A4) cause both Pendred syndrome and DFNB4, two autosomal reces-sive disorders that share hearing loss as a common feature. The hearing loss is associated withtemporal bone abnormalities, ranging from isolated enlargement of the vestibular aqueduct (di-lated vestibular aqueduct, DVA) to Mondini dysplasia, a complex malformation in which thenormal cochlear spiral of 2½ turns is replaced by a hypoplastic coil of 1½ turns. In Pendredsyndrome, thyromegaly also develops, although affected persons usually remain euthyroid. Weidentified PDS mutations in the proband of 14 of 47 simplex families (30%) and nine of 11multiplex families (82%) (P=0.0023). In all cases, mutations segregated with the disease state inmultiplex families. Included in the 15 different PDS allele variants we found were eight novelmutations. The two most common mutations, T416P and IVS8+1G>A, were present in 22%and 30% of families, respectively. The finding of PDS mutations in five of six multiplex familieswith DVA (83%) and four of five multiplex families with Mondini dysplasia (80%) implies thatmutations in this gene are the major genetic cause of these temporal anomalies. Comparativeanalysis of phenotypic and genotypic data supports the hypothesis that the type of temporal boneanomaly may depend on the specific PDS allele variant present. Hum Mutat 17:403–411,2001. © 2001 Wiley-Liss, Inc.

KEY WORDS: ARNSHL; Pendred syndrome; PDS; deafness, nonsensory autosomal recessive; DFNB4;genotype–phenotype; goiter

DATABASES:

SLC26A4 – OMIM: 274600, 600791 (DFNB4); GDB:5584511; HGMD: PDS

INTRODUCTION

Pendred syndrome (PDS; MIM# 274600) isan autosomal–recessive disorder caused by mu-tations in the PDS gene. The syndrome is char-acterized by sensorineural hearing loss and goiter.Classically, deafness is congenital, and thyro-megaly presents in the second decade. The hear-ing loss is associated with temporal bone

Received 6 November 2000; accepted revised manuscript 19January 2001.

*Correspondence to: Richard J.H. Smith, M.D., MolecularOtolaryngology Research Laboratories, Department of Otolaryn-gology–Head and Neck Surgery, 200 Hawkins Dr., Iowa City, IA52242. E-mail: richard-smith@uiowa.edu

Contract grant sponsors: Office of Research and Development;Department of Veterans Affairs; March of Dimes Birth DefectsFoundation; Contract grant sponsor: NIH; Contract grant num-bers: RO1-DC02842; HG00457.

404 CAMPBELL ET AL.

abnormalities that range from isolated enlarge-ment of the vestibular aqueduct (dilated vesti-bular aqueduct, DVA) to Mondini dysplasia, acomplex malformation in which, in addition toDVA, the normal cochlear spiral of 2½ turns isreplaced by a hypoplastic coil of 1½ turns. Bothabnormalities can be diagnosed by either com-puted tomography or magnetic resonance imag-ing [Phelps et al., 1998].

The thyromegaly seen with Pendred syn-drome is the result of multi-nodular goitrouschanges in the thyroid gland, which can growto massive proportions. Affected persons usu-ally remain euthyroid, with triiodothyronine,free serum thyroxine, and thyrotropin levels inthe normal to high-normal range. However,serum thyroglobulin levels may be elevated andthe perchlorate challenge tends to show exces-sive release of iodine from the thyroid gland.This latter test uses perchlorate to displace in-travenously infused radiolabeled iodide fromthe thyroid gland as a measure of iodideorganification. Normally, because iodide is rap-idly bound to thyroglobulin, the discharge ofunincorporated iodide is less than 10%. In per-sons with Pendred syndrome, the discharge isgreater than 15% and can be as high as 80%[Kabakkaya et al., 1993; Gorli, 1995; Morgansand Trotter, 1958; Reardon et al., 1997].

Mutations in PDS also cause DFNB4 (MIM#600791), a type of autosomal recessive non-syndromic hearing loss (ARNSHL) [Li et al.,1998]. By definition, persons with DFNB4 can-not have associated thyromegaly. No other ab-normal physical finding co-segregates with theirhearing loss. However, imaging studies may re-veal abnormal inner ear development, especiallyDVA [Li et al., 1998].

Whether particular PDS mutations are asso-ciated with specific inner ear malformations isnot known. The phenotypic differences observedbetween Pendred syndrome and DFNB4 may re-flect the functional consequences of PDS allelevariants, the genetic background on which theseallele variants are found, or the effects of exter-nal factors. In the field of hearing research, thereis precedence for each of these interactions. Forexample, depending on the mutation in MYO7A(MIM# 276903), the consequence can be

USH1B (MIM# 276903), DFNB2 (MIM#600060), or DFNA11 (MIM# 601317) [Weilet al., 1995, 1997; Liu et al., 1997]; persons ho-mozygous for the 35delG allele variant of GJB2(MIM# 121011) usually, but not invariably,have severe-to-profound deafness [Green et al.,1999]; and carriers of the A1555G mitochon-drial DNA transition (see MTRNR1; MIM#561000.0001) are at-risk for aminoglycoside-in-duced hearing loss [Prezant et al., 1993].

To determine whether phenotypic and geno-typic data can be correlated in persons with PDSmutations, we completed PDS mutation screen-ing in 72 persons with temporal bone abnormali-ties consistent with either DVA or Mondinidysplasia. In persons in whom mutations wereidentified, we compared the PDS genotype tothe clinical phenotype focusing on results of tem-poral bone computed tomography. We also re-viewed all other reports describing PDSdisease-causing mutations.

MATERIALS AND METHODS

Subject Selection

Persons with DVA or Mondini dysplasia wereascertained clinically based on the presence ofhearing loss and temporal bone computed tomog-raphy or magnetic resonance imaging. In addi-tion to these studies, their evaluation included acomplete history and physical examination. Tobe classified with DVA, enlargement of the vesti-bular aqueduct had to be >1.5 mm at a pointmidway between the endolymphatic sac and thevestibule; to be classified with Mondini dyspla-sia, the cochlea also had to be abnormal, withincomplete partition and a scala communis. Ex-cluded from this study were persons with domi-nant types of hearing loss. In consenting personsmeeting study criteria, PDS mutation screeningwas carried out. All procedures were approvedby the IRB at the University of Iowa.

PDS Mutation Screening

After extracting DNA from whole blood us-ing standard procedures, mutation screening wascompleted by SSCP and direct sequencing of thePDS coding region. In brief, PCR was performedwith 40ng of genomic DNA in a 10 ul reactioncontaining 1 ul buffer (160 mM (NH4)2SO4, 670

PDS GENOTYPE�PHENOTYPE CORRELATIONS 405

mM Tris-HCl pH8.8, 0.1% Tween-20), 1.65 mMMgCl2, 0.4ul of 2.5 mM each dATP, dCTP, dTTP,and GTP, 1 pmol each forward and reverseprimer, 5% w/v Glycerol, and 0.25 U Taq poly-merase (primer sequences available on request).Usual amplification conditions were 94°C for 1min, followed by three sets of 13 cycles each of94°C for 30 sec, 56°C (55°C, set 2; 54°C, set 3)for 30 sec, and 72°C for 30 sec, ending with anextension cycle of 72°C for 10 min, althoughfor some primer pairs adjustments were made tooptimize the PCR reaction. Reaction productswere resolved on either MDE (FMC Biopro-ducts, Rockland, ME) or 6% non-denaturingpolyacrylamide, 10% w/v glycerol gels and visu-alized by silver staining. Sequencing was com-pleted on an Applied Biosystems (ABI, FosterCity, CA) model 373 automated sequencer. Se-quence data were compared to published se-quence for PDS using the Sequencer 3.1 softwareprogram package (Gene Codes, Ann Arbor, MI).

Southern Hybridization

Genomic DNA from select affected personscarrying only a single PDS mutant allele wasrestriction digested with EcoRI, HindIII, or PstIand prepared for Southern blotting, as previ-ously described [Smith et al., 1989]. Hybrid-ization was completed against a battery of nineoverlapping probes covering the coding se-quence of PDS as well as a large portion of in-tronic DNA.

Statistical Analysis

The 2-tailed P values were calculated usingthe Fisher exact test.

RESULTS

Clinical Phenotype

Seventy-two persons from 58 families werediagnosed with DVA or Mondini dysplasia.These persons had hearing loss and temporalbones abnormalities confirmed by either com-puted tomography or magnetic resonance imag-ing. In 47 persons, there were no other affectedfamily members (simplex families). Within thisgroup, 10 persons had unilateral DVA, 23 hadbilateral DVA, and 14 had bilateral Mondinidysplasia. There were no cases of unilateralMondini dysplasia. There were 11 pedigrees inwhich multiple persons were affected (multiplexfamilies) (Table 1).

PDS Mutation Screening

PDS mutation screening was completed on72 affected persons from 58 families. If personswith only unilateral audiometric and temporalbone findings are excluded, these numbers are62 and 48, respectively (Tables 1, 2). Fifteen dif-ferent PDS allele variants were found in 35 per-sons. Of these mutations, seven have beenreported previously and eight are new, bringingto 47 the number of PDS disease-causing muta-tions now known (Table 3). All novel mutationswere confirmed by bi-directional sequencing ofthe relevant exons using a minimum of two dif-ferent PCR amplifications; none was present ina screen of 100 non-affected controls. PDS mu-tations were found in 14 of 47 simplex families(30%) and nine of 11 multiplex families (82%).In all cases, mutations segregated with the dis-ease state in multiplex families (Tables 1, 4, 5).The three most common PDS allele variants,

TABLE 1. Study Population

Simplex families Multiplex families Total familiesTemporal bone anomaly (individuals) (individuals) (individuals)

Total (DVA + Mondini) 47 (47) 11 (25) 58 (72)Total (DVA + Mondini) with PDS mutations 14 (14) 9 (21) 23 (35)DVA (total) 33 (33) 6 (14) 39 (47)

Unilaterals 10 (10) 0 10 (10)Bilaterals 23 (23) 6 (14) 29 (37)

Total DVA with PDS mutations 6 (6) 5 (12) 11 (18)Unilaterals 3 (3) 0 3 (3)Bilaterals 3 (3) 5 (12) 8 (15)

Mondini dysplasiaa 14 (14) 5 (11) 19 (25)Mondini dysplasia with PDS mutations 8 (8) 4 (9) 12 (17)aNo persons had unilateral Mondini dysplasia.

406 CAMPBELL ET AL.

IVS8+1G>A, T416P, and L597S, were foundin seven, five, and three families, respectively(Table 3).

Southern Hybridization

Southern hybridization was completed withgenomic DNA from affected persons in the threemultiplex families segregating only a single PDSallele variant (Table 4). No abnormal hybridiza-tion patterns were detected.

DISCUSSION

Pendrin, the protein encoded by PDS, is ex-pressed in the thyroid gland, kidney, and innerear. Functional studies in Xenopus oocytes and Sf9cells have shown that it transports chloride andiodide, and mediates the exchange of chloride andformate [Scott et al., 1999, 2000]. These differ-ent properties may be important for tissue-spe-cific functions. In the thyroid gland, where it hasbeen immuno-localized to the apical membraneof the thyrocyte [Royaux et al., 2000], pendrinmay allow intracellular iodide to pass into thecolloid space where it can be bound to thyroglo-bulin. In the kidney, it is functionally similar tothe renal chloride/formate exchanger, which isimportant for chloride transport in the proximaltubule. Its role in the inner ear is unknown.

Mutations in PDS cause Pendred syndromeand DFNB4. While these two diseases can bedifferentiated clinically by the association of goi-ter with the former, abnormalities of inner earmorphology, like DVA and Mondini dysplasia,are a shared common feature. Because these tem-poral bone anomalies are congenital, we usedtheir presence as our criteria for subject enroll-ment. We did not routinely obtain any thyroidstudies, which often can be difficult to interpret.Environmental causes of goiter are well knownand can confound phenotyping, as illustrated bya large inbred pedigree from Northeastern Bra-

zil segregating for the 279delT PDS allele vari-ant. All individuals homozygous for this muta-tion had goiters, but so too did 10 of 19heterozygotes WITH 279delT and six of 14 re-lated family members carrying only wild typePDS alleles [Kopp et al., 1999]. In another studyof two Tunisian families with the same PDS mis-sense mutation (L445W), there was again phe-notypic variability with respect to thyroid disease.Eleven L445W homozygotes had goiters, but inseven, perchlorate discharge tests were normal,suggesting another etiology for the thyromegaly.However, of the eight L445W homozygotes whounderwent temporal bone computed tomogra-phy, all had DVA. There were no cases of Mon-dini dysplasia [Masmoudi et al., 2000].

Of the 72 persons from 58 families with ei-ther DVA or Mondini dysplasia who we stud-ied, 35 persons (49%) from 23 families (40%)carried PDS mutations. In the 47 simplex fami-lies (DVA, 33; Mondini, 14), the prevalence ofPDS mutations was only 30% (DVA, six of 33(18%); Mondini, eight of 14, (57%)), but in themultiplex families, the number jumped to 82%(DVA, five of six (83%); Mondini, four of five(80%)) (P=0.0023). In all cases, mutations seg-regated with the disease in multiplex families.

These data suggest that the major geneticcause of DVA and Mondini dysplasia is muta-tions in PDS. Because simplex cases include bothgenetic and non-genetic causes of DVA andMondini dysplasia, a corollary is that most of thesporadic cases of DVA (∼80%) and many of thesporadic cases of Mondini dysplasia (∼40%) arenot genetic and therefore unlikely to recur in afamily (Table 2). This fact can be used to modifyrecurrence risks.

To date, 47 different PDS allele variants havebeen reported in 116 different families, but only12 of these mutations have occurred in morethan one family (Table 3). The most frequent,L236P (16%), T416P (15%), and IVS8+1G>A(14%), account for about half of all PDS dis-ease-causing alleles. In this study, while we foundT416P and IVS8+1G>A in 22% and 30% offamilies carrying PDS mutations, respectively,L236P segregated in only two families (9%). LikeCoyle et al. [1998], we were unable to find twomutations in several families, and observed single

TABLE 2. Percentage of Families With PDS Mutations byTemporal Bone Findings

Temporalbone finding Simplex Multiplex Overall

Unilateral DVA 30 None 30Bilateral DVA 13 83 28Total DVA 18 83 28Mondini dysplasia 57 80 63

PDS GENOTYPE�PHENOTYPE CORRELATIONS 407

mutations more commonly in simplex families(11 of 14 simplex families vs three of nine multi-plex families, P=0.077). Southern hybridizationfailed to identify abnormalities in the three mul-tiplex families segregating for only one PDS al-lele variant (families 2180, 7040, 8210), althoughhaplotype analysis in two of these families (2180,

7040) suggests that a disease-causing intronicor promoter mutation still may be present.

To explore possible genotype–phenotype cor-relations, in an earlier study we tested the func-tional significance of select PDS mutations andfound that neither L236P- nor T416P-contain-ing proteins have demonstrable ability to trans-

TABLE 3. PDS Mutations

Nucleotide Amino acid Families in Other families TotalExon change change this study (references) families

2 85G>C E29Q 1 0 13 279delT X96 0 1 [Kopp et al., 1999] 14 314A>G Y105C 1 0 14 317C>A A106D 1 0 14 336–337insT X180 0 1 [Coyle et al., 1998] 14 412G>T V138F 1 1 [Van Hauwe et al., 1998] 24 IVS4+7A>G X141 0 1 [Lopez-Bigas et al., 1999] 15 416G>C G139A 0 1 [Lopez-Bigas et al., 1999] 15 580C>T T193I 0 1 [Adato et al., 2000] 16 626G>T G209V 2 1 [Lopez-Bigas et al., 1999] 36 707T>C L236P 2 17 [Van Hauwe et al., 1998; 19

Coyle et al., 1998]6 753–756delCTCT X286 0 1 [Coyle et al., 1998] 17 783–784insT X286 1 0 17 811G>C D271H 0 1 [Van Hauwe et al., 1998] 17 917delT X308 0 1 [Usami et al., 1999] 15′ Int 7 IVS7+1G>A Splice donor 0 1 [Coyle et al., 1998] 15′ Int 8 IVS8+1G>A Splice donor 7 9 [Coyle et al., 1998; Everett et al., 1987] 169 1003T>C F335L 1 0 19 1105A>G K369E 0 1 [Usami et al., 1999] 19 1115C>T A372V 0 1 [Usami et al., 1999] 19 1149delC FS383 0 1 [Van Hauwe et al., 1998] 1

10 1151A>G E384G 0 6 [Coyle et al., 1998] 610 1197delT FS400 0 5 [Van Hauwe et al., 1998; Everett

et al., 1987; Fugazzola et al., 2000] 510 1226G>A R409H 0 1 [Van Hauwe et al., 1998] 110 1229C>T T410M 0 1 [Coyle et al., 1998] 110 1246A>C T416P 5 12 [Van Hauwe et al., 1998; Coyle et al., 1998] 1711 1284–1286delTGC A429del 0 1 [Coyle et al., 1998] 111 1334T>G L445W 0 3 [Van Hauwe et al., 1998; Masmoudi et al., 3

2000]12 1334–1335insAGTC X467 0 1 [Coyle et al., 1998] 112 1341delG X454 0 1 [Everett et al., 1987] 113 1440T>A V480D 1 0 113 1489G>A G497S 0 1 [Li et al., 1998] 113 1523C>A T508N 0 1 [Bogazzi et al., 2000] 113 1536–1537delAG X524 0 1 [Coyle et al., 1998] 114 1588T>C Y530H 2 1 [Coyle et al., 1998] 315 1667A>G Y556C 0 1 [Van Hauwe et al., 1998] 115 1694G>A C565Y 0 1 [Van Hauwe et al., 1998] 116 1790T>C L597S 3 0 317 1898delA FS634 0 1 [Van Hauwe et al., 1998] 117 1958T>C V653A 1 0 117 2000T>G F667C 0 1 [Everett et al., 1987] 117 2015G>T G672E 2 1 [Coyle et al., 1998] 319 2111insGCTGG X722 0 1 [Usami et al., 1999] 119 2127delT X719 0 1 [Coyle et al., 1998] 119 2162C>T T721M 0 1 [Usami et al., 1999] 119 2168A>G H723R 0 2 [Van Hauwe et al., 1998; Usami et al., 1999] 219 2182–2183insG Y728X 0 1 [Fugazzola et al., 2000] 1

Novel mutations are shown in boldface type.

408 CAMPBELL ET AL.

port iodide or chloride. In contrast, three otherPDS mutations, V480D, V653A, and the doublemutant I490L/G497S, retain residual transportfunction. These findings led us to propose thatspecific mutations could impact variances seenin thyroid function, with residual PDS activity

offering protection against goiter development[Scott et al., 2000].

To determine whether the degree of inner eardysplasia correlates with the PDS genotype, wereviewed clinical findings in all multiplex fami-lies and those simplex families segregating forthe three most common PDS allele variants inthis study (IVS8+1G>A, T416P, L597S) (Tables4, 6). Among multiplex families in which sev-eral affected persons had imaging studies, therewas concordance for the type of temporal bonemalformation in four of five sibships (concor-dant: 2180, 8230, 8300, 8430; discordant: 8330).Across families, we also found the type of tem-poral bone malformation was similar for familiesin which T416P or L597S was segregating with-out IVS8+1G>A (T416/+ twice; T416/E29Q;T416P/G209V; L597S/+ three times). However,among eight affected persons from the sevenfamilies segregating for the IVS8+1G>A mu-tation, computed tomograms showed one nor-

TABLE 4. Mutations in Multiplex Families

Family Allele one Allele two* Phenotype (individual in family)

2180 T416P + Audiogram - profound (1); moderate (2)Inner ear - DVA (1, 2)Thyroid - normal (1, 2)Other - branchial tag and pit (1)

7040 V138F + Audiogram - profound (1); asymmetric moderate andprofound (2)

Inner ear - MondiniThyroid - normal (9 y/o (1); 11 y/o (2))

7090 IVS8+1G>A G672E Audiogram - profound (1); moderate-to-severe (2)Inner ear - Mondini (1)Thyroid - goiter (1)

8210 IVS8+1G>A + Audiogram - profound (1); moderate (2)Inner ear - DVA (1)Thyroid - normal (6 y/o (1); 3 y/o (2))

8220 G209V T416P Audiogram - mild downsloping to severeInner ear - DVAThyroid - normal (23 y/o)

8230 E29Q T416P Audiogram - mild downsloping to severe (1); moderatedownsloping to profound (2, 3)

Inner ear - DVA (1, 2, 3)Thyroid - normal (17 y/o (1); 14 y/o (2); 8 y/o (3))Other - small ears with over-folded helix (1, 2, 3)

8300 G672E G672E Audiogram - profound (1, 2)Inner ear - DVA (1, 2)Thyroid - normal (6 y/o (1); 2 y/o (2))

8330 A106D IVS8+1G>A Audiogram - profound (1); profound (2)Inner ear - Mondini (1); normal (2)Thyroid - normal (5 y/o fraternal twins)

8430 G209V L236P Audiogram - profound (1); severe (2)Inner ear - Mondini (1, 2)Thyroid - goiter (1); normal (2)Other - abnl malleus (1); preauricular pit (2)

*+, wild-type allele.

TABLE 5. Mutations in Simplex Families

Inner earFamily Allele one Allele two* abnormality

5140 V653A + DVA7050 IVS8+1G>A 783–784insT Mondini7070 Y530H + Mondini7080 IVS8+1G>A + Mondini7100 Y530H + Mondini7220 T416P IVS8+1G>A Mondini8050 L236P V480D Mondini8080 T416P + DVA8090 F335L + DVA8120 Y105C + Mondini8150 L597S + DVA8250 L597S + DVA8290 L597S + DVA8440 IVS8+1G>A + DVA

*+, wild-type allele.

PDS GENOTYPE�PHENOTYPE CORRELATIONS 409

mally developed temporal bone (IVS8+1G>A/A106D), three DVAs (IVS8+1G>A/+ twice;IVS8+1G>A/783-784insT) and four Mondinidysplasias (IVS8+1G>A/+; IVS8+1G>A/A106D; IVS8+1G>A/T416P; IVS8+1G>A/G672E). In family 8330, for example, of the twosiblings carrying the IVS8+1G>A and A106DPDS allele variants, one had Mondini dysplasiawhile the other had normal temporal boneanatomy. Examples of intrafamilial variability alsohave been reported by Phelps et al. [1998] in astudy that included 15 sibships with a clinical di-agnosis of Pendred syndrome. Although 10 sibshipswere concordant for the type of temporal bone mal-formation, five were radiologically discordant; un-fortunately, genotypic data were not included.

We found no concordance for audiogramconfiguration, and noted even interaural dif-ferences in some families (Tables 4, 6; 7040,8080). Most persons were too young to makeclinical comparison of thyroid size meaningful[Reardon et al., 1999]. We were precluded fromdoing a similar comparison of previously re-ported families carrying the three most com-mon PDS mutations (IVS8+1G>A, T416P,L236P; Table 3) as sufficiently detailed pheno-typic data were not available.

Our findings, though limited, confirm that aspectrum of cochlear malformations is associatedwith PDS mutations. It also appears that somePDS mutations may be associated with specifictemporal bone anomalies. Similar results havebeen reported by Masmoudi et al. [2000], whostudied two families segregating for L445W andfound that while there was phenotypic variabil-ity with respect to thyroid findings within eachfamily, in all persons in both families in whomtemporal bone imaging was performed, onlyDVA was found.

Based on these data, we hypothesize that PDSfunction affects fluid homeostasis in the mem-branous labyrinth, which in turn affects devel-opment of the bony labyrinthine. This hypothesisis consistent with RNA in situ hybridizationstudies that show Pds expression in cells through-out the endolymphatic duct and sac and in sev-eral other discrete areas, in particular in a regionnear the spiral prominence that plays a role influid homeostasis and fluid resorption [Everettet al., 1999]. Additional functional studies ofPDS allele variants complemented by detailedclinical evaluations of persons carrying thesemutations are necessary to determine whetherthis hypothesis is correct.

TABLE 6. Phenotypes in Simplex Families With IVS8+1G>A, T416P or L597S Mutations

Family Pt age Allele one Allele two* Phenotype

7050 8 IVS8+1G>A 783-784insT Audiogram - profoundInner ear - DVAThyroid - goiter

7080 5 IVS8+1G>A + Audiogram - profoundInner ear - MondiniThyroid - normal

7220 5 IVS8+1G>A T416P Audiogram - profoundInner ear - MondiniThyroid - goiter

8080 4 T416P + Audiogram - high frequency severe, I; moderate, rInner ear - DVAThyroid - normal

8150 12 L597S + Audiogram - profoundInner ear - DVAThyroid - normal

8250 8 L597S + Audiogram - normal downsloping to severeInner ear - DVAThyroid - normal

8290 6 L597S + Audiogram - mild downsloping to severeInner ear - DVAThyroid - normal

8440 1 IVS8+1G>A + Audiogram - moderateInner ear - DVAThyroid - normal

*+, wild-type allele.

410 CAMPBELL ET AL.

ACKNOWLEDGMENTS

This work was supported by grants from NIH(RO1-DC02842 to R.J.H.S., and HG00457 toV.C.S.), and March of Dimes Birth Defects Foun-dation (to L.P.K.).

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