Localization of the bronx waltzer (bv) deafness gene to mouse
Tracy J. Bussoli, Annemarie Kelly, Karen P. Steel
MRC Institute of Hearing Research, University Park, Nottingham NG7 2RD, UK
Received: 3 March 1997 / Accepted: 30 May 1997
Abstract. The bronx waltzer (bv) mutation is an autosomal reces-
sive mutation that is manifested as head tossing and circling in the
mouse. The mutation affects the inner hair cells (IHCs) and pillar
cells in the organ of Corti of the cochlea and the maculae and
cristae of the vestibular part of the inner ear. IHCs begin to de-
generate by a controlled mechanism of cell death as early as ges-
tational day 17 (G17) in the basal coil of the cochlea, and few
surviving IHCs are seen in the adult. As a first step towards the
identification of bv, we analyzed a total of 20 loci in 118 mice from
an intraspecific backcross giving the gene order: centromere–
D5Mit1–D5Mit73–D5Mit55–[D5Mit12, Nds4 (Afp)]–D5Mit87–
[D5Mit205, 20, 88, 208, 93–D5Mit338]–D5Mit25–D5Mit209–bv–
D5Mit188–D5Mit367–D5Mit95–D5Mit43–D5Mit102. A total of
701 mice were then analyzed for the markers D5Mit93 and
D5Mit95, defining a region of 12.08 cM flanking bv. Mice that
were recombinant between D5Mit93 and D5Mit95 were analyzed
for D5Mit338, D5Mit25, D5Mit209, bv, D5Mit188, and D5Mit367.
bv maps 0.14 cM distal of the marker D5Mit209 and 1.14 cM
proximal of the marker D5Mit188 in 701 backcross progeny.
One in 1000 people is born with a significant hearing impairment,
and about half of these are due to a genetic defect, making this
condition the most commonly inherited human sensory defect
(McKusick 1992). In 70% of human cases the deafness exists as
the sole clinical distinguishing feature, unassociated with the broad
range of clinical signs seen in syndromic deafness (Bergstrom et
al. 1971). In the majority of cases of nonsyndromic deafness, the
mode of inheritance is autosomal recessive, and the mutations
often affect the neuroepithelium including the organ of Corti. Con-
certed efforts are being made to localize the genes responsible for
nonsyndromic deafness within the human population, but the
mouse also provides a good model for deafness, and many groups
are putting efforts into localizing deafness genes in the mouse
(Steel 1995). The bronx waltzer mouse is one such autosomal
recessive model in which the mutation affects the neuroepithelia.
The bronx waltzer mutation arose spontaneously and causes
hearing impairment and vestibular defects in mice (Deol and
Gluecksohn-Waelsch 1979). Homozygous mice show typical
‘shaker-waltzer’ type behavior, which is manifested by hyperac-
tivity, jerking of the head, and circling. The mutation primarily
affects the inner hair cells (IHCs), and secondary effects include
outer hair cell (OHC) and pillar cell disorganization (Deol 1981;
Demeˆmes and Sans 1985; Whitlon et al. 1996; Bussoli 1996).
IHCs are present at gestational day 17 (G17) but begin to degen-
erate in the basal coil between G17 and birth (Bussoli et al. in
preparation) until in the adult about 20–25% have been estimated
to remain (Lenoir and Pujol 1984). Electrophysiological responses
are abnormal in this mutant with absent or small compound action
potential responses (CAP), small cochlear microphonic responses
(CM), and small positive summating potentials (SP) compared
with heterozygous controls (Bock et al. 1982).
The organ of Corti abnormality in bronx waltzer is unique
among mouse mutants described to date, as it involves a primary
defect of the inner hair cells, while most neuroepithelial mutants
show primary defects in both inner and outer hair cells. The im-
portance of the inner hair cells as the cells mainly, if not exclu-
sively, responsible for initiating cochlear nerve action potentials
suggests that the bronx waltzer gene will be a particularly inter-
esting gene to clone and identify. Because there is no obvious
candidate gene and no obvious biochemical product associated
with this mutation, we have decided to adopt a positional cloning
strategy as a first step towards cloning the bronx waltzer gene.
Unpublished data from a small backcross suggested that bv might
be on Chr 5 (R. Brister, personal communication) so we looked for
linkage to Chr 5 markers as a first step. In this study, we have used
an intraspecific backcross of 706 mice to generate a detailed ge-
netic linkage map around the bv locus and show that it does lie on
Chr 5. The BXD recombinant inbred strains were also used to
generate a linkage map around some of the SSLP markers that
were close to bv.
Materials and methods
Mice carrying the bv mutation were originally obtained from M.S.
Deol. Details of the genetic background were not available, and the mice
were maintained at Nottingham on their original background.
Preparation of DNA and PCR.
Genomic DNA was prepared from tail
and ear pinna skin. The polymerase chain reaction (PCR) was carried out
with 0.25–0.5 g of mouse genomic DNA, 1 × PCR buffer (Promega), 2
, 0.2 m
PCR primers (Research Genetics,
Huntsville), and 2.5 units Taq polymerase (Perkin Elmer, Applied Biosys-
tems, Cheshire, UK) in a 20-l volume. Cycle parameters were 94°C for
15 s, 55°C for 2 min, and 72°C for 2 min for 40 cycles. PCR products were
analyzed by electrophoresis on 3% Metaphor agarose gels stained with
Genetic background of bronx waltzer stocks.
35 primer pairs (Re-
search Genetics) along the length of Chr 5 at an average spacing of 2 cM
were chosen to amplify DNA from bronx waltzer and the mouse strains
C3H/HeJ, C57BL/6J, BALBc, CBA/Ca, 101/H (these strains were all
available for outcrossing). The PCR product sizes from bronx waltzer and
these strains were compared. The most divergent laboratory strain was used
in the intraspecific backcross.
Correspondence to: K.P. Steel
© Springer-Verlag New York Inc. 1997Mammalian Genome 8, 714–717 (1997).