Am. J. Hum. Genet. 55:685-694, 1994 A New Nonsyndromic X-linked Sensorineural Impairment Linked to Xp2 1.2 Anil K. Lalwani, J. Rodney Brister, Jorgen Fex, Kenneth M. Grundfast, Anita T. Pikus, Barbara Ploplis, Theresa San Agustin, Hana Skarka, and Edward R. Wilcox

Laboratory of Molecular Genetics, National Institute on and Other Communication Disorders, National Institutes of Health, Public Health Service, Bethesda

Summary affects 4-11 of 10,000 children (Bodurtha and Nance X-linked deafness is a rare cause of hereditary hearing im- 1988). During the past 25 years, the proportion of hearing pairment. We have identified a family with X-linked dom- impairment attributed to heredity has steadily increased, inant sensorineural hearing impairment, characterized by as environmental and infectious etiologies have been incomplete penetrance and variable expressivity in carrier effectively controlled. A recent survey, the 1988-89 Gal- females, that is linked to the Xp21.2, which contains the laudet University Annual Survey of Hearing Impaired Chil- Duchenne muscular dystrophy (DMD) locus. The audi- dren and Youth, attributed 62.8% of early-onset deafness tory impairment in affected males was congenital, bilat- to genetic causes (Marazita et al. 1993). The majority eral, profound, sensorineural, affecting all frequencies, (- 80%) of hereditary deafness is inherited in a recessive and without evidence of radiographic abnormality of the manner, and a dominant mode of inheritance is implicated temporal . Adult carrier females manifested bilateral, in 15%-20% of cases (Grundfast and Lalwani 1992). mild-to-moderate high-frequency sensorineural hearing X-linked deafness is a less common form of hereditary impairment of delayed onset during adulthood. Eighteen hearing impairment, accounting for only -1.7% of ge- commercially available polymorphic markers from the X netic cases (Fraser 1965). Empirical observations have doc- chromosome, generating a 10-15-cM map, were initially umented that males who are deaf outnumber females who used for identification of a candidate region. DXS997, lo- are deaf. A variety of X-linked syndromes or contiguous- cated within the DMD gene, generated a two-point LOD gene syndromes have been associated with deafness, in- score of 2.91 at 9 = 0, with every carrier mother hetero- cluding mental retardation, , congenital zygous at this locus. Recombination events at DXS992 (lo- adrenal hypoplasia, hypogonadism, and choroideremia cated within the DMD locus, 3' to exon 50 of the dys- (Myhre et al. 1982; Mattei et al. 1983; Francke et al. 1987; trophin gene) and at DXS1068 (5' to the brain promoter Davies et al. 1988; Zachmann et al. 1992; Fries et al. 1993; of the dystrophin gene) were observed. No recombination Malmgren et al. 1993; Saugier-Veber et al. 1993). Com- events were noted with the following markers within the pared with syndromic X-linked deafness, nonsyndromic DMD locus: 5`DYS II, intron 44, DXS997, and intron 50. X-linked deafness is less common. In the majority of the There was no clinical evidence of Duchenne or Becker pedigrees with nonsyndromic X-linked deafness, the hear- muscular dystrophy in any family member. It is likely that ing impairment is of prelingual onset (Reardon et al. this family represents a new locus on the X chromosome, 1992b) and is categorized as either X-linked fixation of the which when mutated results in nonsyndromic sensorineu- stapes with perilymphatic gusher associated with mixed ral and is distinct from the heterogeneous hearing impairment (DFN3; perilymphatic gusher-deaf- group of X-linked hearing losses that have been pre- ness syndrome [MIM 304400; McKusick 1993]) (Nance et viously described. al. 1970, 1971) or congenital sensorineural deafness (MIM 304500; McKusick 1993) (Fraser 1965). Both forms of Introduction nonsyndromic hearing impairment have been linked to Xql3-q21.2 (Bach et al. 1992; Reardon et al. 1992a). It is Hereditary hearing impairment is responsible for 50%- possible that these two clinically different forms of deaf- 60% of cases of profound early-onset deafness, which ness arise from mutations within the same gene (Reardon et al. 1992b). High-frequency sensorineural deafness Received January 12, 1994; accepted for publication June 17, 1994. (MIM 304600; McKusick 1993) (Livan 1961; Wellesley Address for correspondence and reprints: Edward R. Wilcox, Labora- and Goldblatt 1992) and progressive sensorineural deaf- tory of Molecular Genetics, NIDCD, NIH, Building 36, Room SD-08, ness (MIM 304700; McKusick 1993) (Mohr and Mageroy 9000 Rockville Pike, Bethesda, MD 20892. © 1994 by The American Society of Human Genetics. All rights reserved. 1960; Pelletier and Tanguay 1975) have postlingual onset 0002-9297/94/5504-001 1$02.00 and have not been linked to a specific region of the X chro-

685 I

1 2

a b c DXS989

a b c DXS992

a b c DXS997

a b c DXS1068

a b c DXS993

I - --- I 1

1 2 3 4 5

d a b b C eO d a b c e e d a c cl e e d a c Icl e e d a c IjC e e

g i . I

1 2 4 5 6 7 8 9 10 11 12

d b b b a ad e c 0 f 41 e c e d b b b a a d e e .c e f d a c c a a d e e c e f d a c c a a d e e c e f d a c c a ad e e c e f 6 7 e e e e Ic e IV e Ic e 1 2 3 4

Profound, bilateral a d C f C sensorineural hearing loss a d 0

O Delayed onset, high frequency a d sensorneural hearing loss a a C e ~ ~ ~ ~It~ ~ ~ ~ - - Mild-moderate aenaorineumil a a e e tM hearing loss

Hearing loss, unknown ( ) severity

NK Proband

Figure I Pedigree of family 47 with X-linked nonsyndromic sensorineural hearing loss. Subject numbers are shown below the pedigree symbols. Genotype analysis of family members for five fully informative markers (DXS989, DXS992, DXS997, DXS1068, and DXS993) from Xp shows the centromeric and telomeric crossovers around DXS997. The first-generation paternal chromosome has been assigned all a alleles. The maternal chromosomes have been assigned all b and c alleles. Subsequent generations have been assigned appropriate alleles for each locus, on the basis ofthe inherited genotype ofeach individual. This analysis shows that the c allele at DXS997 is present in all affected and carrier individuals, with crossovers on either side. Lalwani et al.: Nonsyndromic X-linked SNHI Linked to Xp21.2 687 mosome. There is a report of one family with congenital 22.3 sensorineural X-linked deafness that is not linked to Xql3- DXSW q21.2 (Reardon et al. 1991; pedigree 7). There are no re- .13 222 U ported differences, in the clinical features of this family, 22.1 DUDW UTR .03 DXS8 /- DXSS DX80G2 from other reported families with congenital sensorineural .13 21.3 deafness. In this report, we identify a novel form of X- 21.2 DXSW7 linked nonsyndromic deafness linked to Xp21.2, which .08s 21.1 \DMD44 .08. DMD5 DYSII contains the Duchenne muscular dystrophy (DMD) locus. .09 DXBDMDS'DYSIID8 AM DX85#B .01 DXBIO68 11o .09 Patients, Material, and Methods DXS1 11.23 .11 1122 1121 Patients 11.1 .13 DX8100 11.1 Twenty-nine members of three generations of a four- 11.2 generation family (family 47) including five affected males .0. 12 four affected females were available for examination DXSOBS and 1 I3 j DX8441 DXS73SI DXVS 1/4 (fig. 1). Complete audiologic assessment, including pure- .03 tone thresholds, speech-reception thresholds, and speech discrimination scores, was performed in standard sound- .15 21.1 I 21.2 isolated diagnostic suites. Additional tests in selected pa- DXS178* tients included auditory brain stem response and oto- -21.3 25 acoustic emission test. One affected male underwent com- I .;22.1 puted tomography of the temporal bone, for evaluation of .22.2 -DXSIOOI the inner ear. G-banding of prometaphase chromosomes .09 223 providing 850-band resolution was performed on four of -DX77 i 24 the affected males. DXSO4I .13 .25 Samples DX898 I Twenty to 40 ml of venous blood was collected from ,.19 26 DXS1I14 each consenting individual. Genomic DNA was prepared DX8292 from leukocytes. Lymphoblastoid cell lines were estab- 0x8998 I .2? lished and stored in liquid nitrogen as a permanent source of material (Anderson and Gusella 1984). 28 DXSI108 PCR Analysis Eighteen commercially available primer pairs detecting Figure 2 Physical and genetic map of the X chromosome, show- ing the relative positions of the microsatellite polymorphic markers used microsatellite polymorphisms on the X chromosome (Re- to establish linkage. Sex-averaged recombination fractions are taken search Genetics) and generating a 5-15-cM map were ini- from published sources (NIH/CEPH Collaborative Mapping Group tially used as a basis for identification of a linkage region 1992; Wiessenbach et al. 1992; Matise et al. 1994; Donnelly et al., in (fig. 2). The family was also typed for the following mark- press). ers or locations from the DMD region: 5'DYSII from the brain dystrophin promoter (Feener et al. 1991), intron 44 gM of each dNTP, 0.05 U of thermostable AmpliTaq (Clemens et al. 1991), DXS997, intron 50 (Clemens et al. DNA polymerase (Perkin Elmer Cetus), and 1 X PCR Per- 1991), and DXS992, DXS985, and 3'UTR (Beggs and Kun- kin Elmer Cetus PCR buffer. The samples were initially kel 1990; Oudet et al. 1990). Additional primers for poly- denatured at 950C for 5 min and underwent 35 amplifica- morphic markers from the Xql3-21.1 region were also tion cycles (940C for 1 min, 550C for 1 min, and 720C for prepared on an Applied Biosystems 394 DNA/RNA syn- 1 min) followed by final extension for 7 min at 720C. Five thesizer (Applied Biosystems), to evaluate possible linkage microliters of loading buffer (10:1 formamide-bromophe- to this region that includes the gene for the perilymphatic nol blue:xylene cyanole FF) were added to the reaction gusher-deafness syndrome (DFN3). Markers important for mixture after PCR. The samples were denatured for 5 min establishing or excluding linkage were run twice to con- at 950C, and 4 jl were loaded onto Sequagel-6 gel (6% firm genotypes. PCR reactions were carried out using a denaturing polyacrylamide/urea gel; National Diagnos- PCR kit (Perkin Elmer Cetus), in a final volume of 10 gI tics). After electrophoresis, the gels were dried for 1 h at containing 20 jg of genomic DNA, 1 pmol of each primer, 80'C and were autoradiographed for 4-12 h at room tem- 0.2 pmol of one primer end-labeled with [y_32p] dATP, 25 perature. 688 Am. J. Hum. Genet. 55:685-694, 1994

AUDIOGRAM Hearing Levels re: ANSI 1969 (R1i971) Frequency in Hertz 125 250 500 750 1000 1500 2000 e 4000 8000 T~oI I 3om mmoo -10l ll -10 0

1120 10 20 20 10 __i 30

3020 40_01I_ _ 40 50 60~~~~~~~~~ 0 60 60~~~~~~~~~~~~~~~7 70 70 80 8 80 90 90 100 10S.1(M)SMsItM.iagew69 AkLl. lin1} MK1 LEVEL n d 110 MASKING LEVEL In dB 4 -

Figure 3 Audiogram of a 69-year-old male (11-4) showing profound bilateral sensorineural hearing impairment

Linkage Analysis out evidence of radiographic abnormality of the temporal LINKAGE program package version 5.01 adapted for bone (fig. 3). Karyotyping at 850-band resolution showed the National Institutes of Health Convex computer was no deletions or structural abnormalities in four affected used to perform both pairwise and multipoint linkage males. Carrier females manifested bilateral, mild-to-mod- analysis (Lathrop et al. 1984). Dominant X-linked inheri- erate (20-50 dB) high-frequency, sensorineural hearing im- tance with incomplete (80%) penetrance in the carrier fe- pairment, which appeared earliest in a 35-year-old carrier male was assumed. Affection status of carrier females with- female (fig. 4). The hearing impairment first became evi- out hearing impairment who were <30 years of age was dent in the third decade of life and was present in 80% assumed to be unknown. SLINK simulation was run to (four of five) of the adult carrier females. A 16-year-old determine the maximum LOD score obtainable with this carrier female (IV-7) demonstrated mild-to-moderate, bi- family (Ott 1989; Weeks et al. 1990). Two-point linkage lateral sensorineural hearing impairment (fig. 5). analysis between each marker and the disease gene was Initial screening with commercially available primer performed using MLINK, and a multipoint linkage analy- pairs was successful in identifying a region of linkage. sis was performed using LINKMAP from the LINKAGE DXS997 located within the DMD locus on the short arm program package. Locus order and interloci distances of the X chromosome was fully informative, demonstrated were determined from the literature (fig. 2) (NIH/CEPH no crossovers, and gave a two-point LOD score of 2.91 Collaborative Mapping Group 1992; Wiessenbach et al. (table 1). This is the maximum possible LOD score for the 1992; Matise et al. 1994; Donnelly et al., in press). pedigree determined from SLINK analysis when autoso- mal dominant inheritance with 80% penetrance is as- Results sumed. Because of the small size of the family, the true penetrance is uncertain. If either a lesser penetrance of We describe a family with X-linked dominant sensori- 60% or a higher penetrance of 99% is assumed, the respec- neural hearing impairment, with incomplete penetrance tive LOD scores for DXS997 are 2.82 and 3.00, which con- and variable expressivity in carrier females. The auditory tinue to be supportive of linkage. impairment in affected males was congenital, bilateral, pro- The family was typed with additional markers identified found, sensorineural, affecting all frequencies, and with- from this region of the X chromosome, including DXS7, AUDIOGRAM Hearing Levels re: ANSI 1969 (R1i971) Frequency in Hertz 125 250 500 750 1000 15oo 2000 3ooo 4000 6ooo 8000

-10 L |10z -10 0 30 10 20 20 40 30 40 60~~~~~~~~~~~~~~~3 50 45o L ~ ~~~~~~I I so 60 70~~~~~~~~~~~~~~~760 L t r I 170 1~ V 70

80 I 80 1 I R0 L I la < l j l 80 ]I I

. . c9 90

.I M.,C. 100 1 nA _(F) age72 _LL I I...I _____ MASKING LEVEL In dB Figure 4 Audiogram of a 72-year-old female (11-2) showing mild-to-moderate bilateral high-frequency hearing impairment

AUDIOGRAM Hearing Levels re: ANSI 1969 (R1971) Frequency in Hertz

MASKING LEVEL In dB Figure 5 Audiogram of a 16-year-old female (IV-4) showing mild-to-moderate sensorineural hearing loss 690 Am. J. Hum. Genet. 55:685-694, 1994 Table I Family 47: Pairwise LOD Scores

LOD SCORE AT 0 = MAXIMUM Locus 0 .025 .05 .1 .2 .3 .4 MAXIMUM 0 LOD SCORE

DXS996 ...... -4E + 19 -1.19 -.653 -.185 .128 .168 .1 .275 .172 DXS207 ...... -4E + 19 -.751 -.481 -.242 -.068 -.015 -.002 .5 0 DXS987 ...... -4E + 19 -.415 -.158 .052 .164 .147 .082 .225 .167 DXS999 ...... -4E + 19 .441 .663 .799 .749 .55 .287 .125 .81 DXS989 ...... -4E + 19 -.914 -.368 .114 .437 .454 .3 .25 .471 DMD3'UTR ...... -2.74 .15 .394 .577 .623 .509 .299 .175 .632 DXS985 ...... -3.97 -.749 -.468 -.208 -.001 .066 .06 .35 .07 DXS992 ...... -3.42 -.254 -.027 .135 .182 .136 .068 .175 .184 DMDS0 ...... 2.91 2.79 2.66 2.41 1.87 1.28 .648 0 2.91 DXS997 ...... 2.91 2.79 2.66 2.41 1.87 1.28 .648 0 2.91 DMD 44 ...... 1.24 1.19 1.13 1.01 .77 .516 .258 0 1.24 DMDS'DYSII ...... 2.91 2.79 2.66 2.41 1.87 1.28 .648 0 2.91 DXSS38 ...... 1.27 1.21 1.15 1.03 .774 .512 .252 0 1.27 DXS1068 ...... -4E + 19 1.2 1.39 1.46 1.26 .91 .472 .1 1.46 DSX1110 ...... 986 .932 .877 .768 .548 .337 .15 0 .986 DXS993 ...... -4E + 19 -.393 .107 .501 .662 .542 .296 .2 .662 DXS 7 ...... -4E + 19 -1.2 -1.43 -.902 -.444 -.23 -.1 .5 0 DXS1003 ...... -4E + 19 -.393 .107 .501 .662 .542 .296 .2 .662 DXS991 ...... -4E + 19 -3.38 -2.53 -1.72 -.997 -.596 -2.87 .5 0 DXS983 ...... -4E + 19 -.07 .167 .339 .374 .279 .142 .15 .383 DXS986 ...... -4E + 19 -1.15 -.622 -.167 .127 .16 .094 .275 .164 DXS441 ...... -4E + 19 -2.32 -1.74 -1.18 -.661 -.379 -.177 .5 0 DXYS1/4 ...... -4E + 19 -5.33 -3.89 -2.5 -1.24 -.634 -.251 .5 0 DXS738 ...... -4E + 19 -.823 -.55 -.302 -.109 -.036 -.007 .5 0 DXS990 ...... 048 .118 .163 .208 .205 .148 .074 .15 .217 DXS178 ...... -4E + 19 -5.15 -3.88 -2.59 -1.36 -.693 -.273 .5 0 DXS3 ...... -4E + 19 -3.64 -2.51 -1.46 -.58 -.21 -.051 .5 0 DXS1 106 ...... -4E + 19 -1.77 -1.22 -.711 -.294 -.116 -.03 .5 0 DXS1001 ...... -4E + 19 -4.21 -3.03 -1.88 -.827 -.322 -.073 .5 0 DXS425 ...... -4E + 19 -.533 -.27 -.047 .095 .11 .071 .275 .113 DXS737 ...... -4E + 19 -3.35 -2.48 -1.64 -.869 -.463 -.199 .5 0 DXS994 ...... -4E + 19 -4.19 -3.03 -1.93 -.943 -.458 -.175 .5 0 DXS984 ...... -4E + 19 -2.35 -1.66 -.968 -.34 -.068 .029 .425 .033 DXS1114 ...... -4E + 19 -4.57 -3.39 -2.24 -1.15 -.576 -.22 .5 0 DXS292 ...... -4E + 19 -4.21 -3.02 -1.87 -.813 -.311 -.069 .5 0 DXS998 ...... 359 .335 .31 .261 .165 .081 .022 0 .359 DXS1108 ...... -4E + 19 -.896 -.374 .062 .316 .3 .17 .225 .328

DXS993, DXS1110, DXS1068, DXS538, DMD, DXS992, with the centromeric crossover occurring somewhere be- and DXS985. CA polymorphisms from DXS538, the 5' re- tween DXS538 and DXS1068 and with the telomeric gion of DMD (5'DYSII, near the brain promoter), intron crossover occurring somewhere between introrit 50 and 44, and intron 50 demonstrated no crossovers. Fully infor- DXS992 (fig. 1). Multipoint linkage analysis generated a mative markers (5'DYSII and intron 50) gave LOD scores LOD score of 2.91 at DXS997. of 2.91; intron 44 and DXS538 were not fully informative Markers fronm Xql3-q21 were also run, to exclude the but demonstrated no crossovers (table 1). DXS1068, lo- region linked to X-linked fixation of the stapes with peri- cated centromeric or 5' to the dystrophin gene and DX538, lymphatic gusher, associated with mixed hearing impair- did demonstrate one crossover; this marker is within 1.6 ment (DFN3; perilymphatic gusher-deafness syndrome cM of 5'DYSII and DXSS38 (Donnelly et al., in press). Sim- [MIM 304400; McKusick 1993]) and congenital sensori- ilarly, crossovers were observed at markers DXS992, neural deafness (DFN2 [MIM 304500; McKusick 1993]). DXS985, and DMD 3UTR, which are all telomeric or 3' These markers include DXS441, DXYS1/4, DXS738, to intron 50 and within the dystrophin gene. Therefore, DXS983, DXS986, and DXS990. All except DXS990, a the region of linkage is between DXS538 and intron 50, weakly informative marker, demonstrated a LOD score of Lalwani et al.: Nonsyndromic X-linked SNHI Linked to Xp21.269 691

Multipoint LOD Score in the region of Xq2l

0

(In O co iQm 12O o0 0~~~~~~~~~~~~~~~~~G 9. q

Ar -O..* -5 . 0 t ... I*. . U 01 .0 a 0

0

-4 . .III. IIaII. I .II 9 I I I I a I I a a I . . . I -15 II I I

0 -.04 .08 .12 .16 .2 .24 .28 .32

recombination distance

Figure 6 Exclusion of the Xq2l region by multipoint linkage analysis using polymorphic microsatellite markers from this region. Map distances are given in recombination units as shown in fig. 2. DXS991 was arbitrarily set as the zero point on the map. This composite map has been produced from six-point analysis.

-oo at 0 = 0. Multipoint linkage analysis effectively ruled trophin (Hoffman et al. 1987; Koenig et al. 1988). Muta- out linkage in this region, with >10,000:1 odds against tions within the dystrophin gene are responsible for (1) linkage (fig. 6). DMD, (2) the milder, Becker muscular dystrophy (BMD) (Kunkel 1986; Monaco et al. 1986; Koenig et al. 1987), (3) X-linked dilated (Muntoni et al. 1993), Discussion cardiomyopathy and (4) isolated elevation of creatinine phosphokinase

A family has been identified with nonsyndromic senso- (Koenig et al. 1989). rineural hearing impairment that is linked to Xp2l1.2. This Interestingly, two other loci associated with nonsyn- chromosomal region contains the DMD locus. Markers dromic deafness have also been linked to muscular dystro- within the DMD locus generated the maximum two-point phies. A dominant form of nonsyndromic hearing impair-

LOD score of 2.91. For X-linked disorders, a LOD score ment has been linked to the same region of 5q31 as has of 2 is usually considered significant, because the prior dominant limb-girdle muscular dystrophy (Leon et al. odds for linkage are higher. The DMD locus spans 2.3 mil- 1992). Similarly, a recessive form of nonsyndromic hearing lion bp (Kenwrick et al. 1987; Van Ommen et al. 1987; impairment has been linked to the same region of 13q12

Burmeister et al. 1988; Ahn and Kunkel 1993) and has a as has severe childhood autosomal recessive muscular dys- recombination frequency of -9%-14%, which is sixfold trophy (SCARMD) (Azibi et al. 1993; Guilford et al. 1994). higher than the average rate for other regions of compara- The gene responsible for SCARMD likely affects the ex- ble size (Abbs et al. 1990; Oudet et al. 1991, 1992; Don- pression or function of 50-kD dystrophin-associated gly- nelly et al., in press). The only gene identified within the coprotein (DAG), which is known to be absent in these

DMD locus to date encodes the cytoskeletal protein dys- patients (Matsumura et al. 1992). 50-kD DAG is one of 692 Am. J. Hum. Genet. 55:685-694, 1994 several proteins involved in the formation of a transmem- quency within the Duchenne muscular dystrophy gene. Ge- brane complex linking dystrophin to the extracellular sur- nomics 7:602-606 face (Ahn and Kunkel 1993). The linkage of nonsyndromic Ahn AH, Kunkel LM (1993) The structural and functional diver- deafness to muscular dystrophy and regions containing sity of dystrophin. Nature Genet 3:283-291 dystrophin or DAG suggests that mutations in cytoskeletal Allen NR (1973) Hearing acuity in patients with muscular dys- proteins may play an important role in the pathophysiol- trophy. Dev Med Child Neurol 15:500-505 ogy of Anderson MA, Gusella JF (1984) Use of cyclosporin A in estab- hearing impairment. lishing Epstein-Barr virus-transformed human lymphoblastoid The linkage data suggest several possibilities regarding cell lines. In Vitro 20:856-858 the relationship between sensorineural hearing impair- Azibi K, Bachner L, Beckmann JS, Matsumura K, Hamouda E, ment in the reported family and the DMD locus. One pos- Chaouch M, Chaouch A, et al (1993) Severe childhood autoso- sibility is that a novel gene is located within Xp21.2, a gene mal recessive muscular dystrophy with the deficiency of the that when mutated results in nonsyndromic sensorineural 50KDA dystrophin-associated glycoprotein maps to chromo- hearing loss. This new gene may be located either in the some 13q12. Hum Mol Genet 2:1423-1428 large intronic regions of the dystrophin gene (Den Dunnen Bach I, Brunner HG, Beighton P, Ruvalcaba RHA, Reardon W, et al. 1989) or between DXS1068 and the brain promoter Pembrey ME, van der Velde-Visser SD, et al (1992) Microde- of dystrophin. Alternatively, the dystrophin gene itself letions in patients with gusher-associated, X-linked mixed may be mutated. The finding of deafness without associ- deafness (DFN3). AmJ Hum Genet 51:38-44 ated manifestations of DMD or BMD may be explained Beggs AH, Kunkel LM (1990) A polymorphic CACA repeat in by a dystrophin mutation-either in an the 3' untranslated region of dystrophin. Nucleic Acids Res 18: (a) unidentified 1931 -specific dystrophin promoter, in an isoform of Bodurtha JN, Nance WE (1988) Genetics of hearing loss. In: Al- dystrophin that is unique to the cochlea, or (b) within dys- bert PW, Ruben RJ (eds) Otologic medicine and surgery. Vol trophin-which results only in hearing loss. 1. Churchill Livingstone, New York, pp 831-852 Auditory dysfunction has not been implicated in pa- Burmeister M, Monaco AP, Gillard EF, Van Ommen GJB, Affara tients with either DMD or BMD. However, earlier studies NA, Ferguson-Smith MA, Kunkel LM, et al (1988) A 10- of the auditory system in DMD patients were performed megabase physical map of human Xp2l, including the Du- >20 years ago and were limited to assessing pure-tone chenne muscular dystrophy gene. Genomics 2:189-202 hearing levels. The most recent study of auditory function, Clemens PR, Fenwick RG, Chamberlain JS, Gibbs RA, de An- in a population of 51 DMD patients, 24 of whom were drade M, Charkraborty R, Caskey CT (1991) Carrier detection ambulatory, was carried out in 1973. This study demon- and prenatal diagnosis in Duchenne and Becker muscular dys- strated both normal mean pure-tone hearing level for six trophy families, using dinucleotide repeat polymorphisms. Am frequencies between 250 and 6,000 Hz and delayed re- J Hum Genet 49:951-960 sponse to auditory stimulus as a result of delayed muscular Davies KE, Smith TJ, Bundey S, Read AP, Flint T, Bell M, Speer response and not as a result of A (1988) Mild and severe muscular dystrophy associated with prolonged auditory-nerve deletions in Xp2l of the human X chromosome. J Med Genet latency (Allen 1973). Contemporary audiologic testing of 25:9-13 higher-frequency (>8,000 Hz) regions of the cochlea, of Den Dunnen JT, Grootscholten PM, Bakker E, Blonden LAJ, micromechanics of the cochlear partition using otoacous- Ginjaar HB, Wapenaar MC, van Paassen HMB, et al (1989) tic emissions (Kemp 1978), and of retrocochlear function Topography of the Duchenne muscular dystrophy (DMD) with brain stem auditory evoked responses may reveal au- gene: FIGE and cDNA analysis of 194 cases reveals 115 dele- ditory dysfunction in DMD patients. In a similar study of tions and 13 duplications. Am J Hum Genet 45:835-847 the visual system of DMD patients with a sensitive physio- Donnelly A, Kozman H, Gedeon AK, Webb S, Lynch M, Suther- logic measurement of retinal function, i.e., the electroreti- land GR, Richards RI, et al. A linkage map of microsatellite nogram (ERG), Pillers et al. (1993) demonstrated variable markers on the human X chromosome. Genomics (in press) to clinically silent abnormalities of the ERG. Feener CA, Boyce FM, Kunkel LM (1991) Rapid detection of CA polymorphisms in cloned DNA: application to the 5' region of the dystrophin gene. Am J Hum Genet 48:621-627 Acknowledgments Francke U, Harper JF, Darras BT, Cowan JM, McCabe ERB, We thank the family for their willingness to participate in this Kohlschiitter A, Seltzer WK, et al (1987) Congenital adrenal study of hereditary hearing impairment. We thank Dr. Mark hypoplasia, myopathy, and glycerol kinase deficiency: molecu- Schneider for his helpful discussion and for critically reviewing lar genetic evidence for deletions. Am J Hum Genet 40:212- the manuscript. 227 Fraser GR (1965) Sex-linked recessive congenital deafness and References the excess of males in profound childhood deafness. 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