Pendred syndrome model, pdsm, a spontaneous mouse mutation in the Slc26a4 gene with associated inner ear abnormalities.

 Leona H Gagnon, Sandra Gray and Kenneth R Johnson

Source of Support:

DC04301 RR01183

Mutation (allele) symbol:

pdsm

Mutation (allele) name:

Pendred syndrome model

Gene symbol:

Slc26a4

Strain of origin:

BXA7/PgnJ

Current strain name:

BXA7/PgnJ -Slc26a4pdsm/J

Stock #:  00

6816 (view JAX® Mice Data Sheet for additional information including Price and Supply Information)

Phenotype categories:

neurological/behavioral: motor capabilities/coordination/movement anomalies/deafness/head bobbing

Origin and Description

The recessively inherited spontaneous mouse mutation Pendred syndrome model (pdsm) occurred in the inbred BXA-7/PgnJ mouse strain. The mutant phenotype and inner ear pathology is very similar to that of the mouse strain previously described with a targeted disruption of Slc26a4 (Pds) gene (Everett LA., et al 2001). Pdsm mutants are identified at weaning age (3 weeks) by their overt head bobbing and circling behavior and occasional head tilt. The mouse colony is maintained by sister/brother mating of a heterozygous (+/pdsm) female with a homozygous (pdsm/pdsm) mutant male.

A routine pathological screen performed on three mutants and two controls (15-37 weeks), detected inner ear abnormalities including reduced or absent otoconia, hair cells and spiral ganglion cells. Serial cross-sections of the inner ears from a pdsm/pdsm mutant and a +/pdsm control (12 weeks) mice confirmed these abnormalities as well as revealed a malformation of the tectorial membrane, degeneration of the organ of Corti and a displacement of Reissner's membrane enlarging the scala media (fig.1). Whole mount preparations of the inner ears showed a reduction of otoconia in the utriclar and saccular maculae (fig 2), and a variable but always reduced number of cochlear turns, or Mondini malformation, in pdsm/pdsm mutants (fig 3).

Eight mutant mice and six controls were assessed for hearing by auditory brainstem response (ABR) at 29 and 80 days of age. Homozygous mutants were completely deaf with no response to the loudest test stimuli (100dB SPL), while the control littermates retained good hearing.

Partial testicular atrophy was observed in the male mutants evaluated (n=2). Further evaluation of the testis and sperm from two additional mutants revealed that the total concentration and motility of sperm were greatly reduced. However, enough normal sperm must be produced because male fertility in the inbred colony is not significantly altered.

Since human Pendred syndrome patients commonly have thyromegaly due to a lack of sufficient thyroid hormone, the pdsm mice were evaluated for T4 (ug/dl) levels via blood serum chemistry analysis. Pdsm mice did not display any signs of hypothyroidism as determined from either the blood serum chemistry (n=22) or histological analysis (n=5) of the thyroid gland at any age examined (4-53 weeks).

Genetic Analysis

An intercross was performed with CAST/EiJ mice and 48 mutant F2 animals were analyzed. Using our standard mapping practice, the mutation was mapped to a region of chromosome 12 between markers D12Mit136 (30.7 Mb) and D12mit154 (39.6 Mb). Included in this region is the gene Slc26a4 (32.1 Mb, position based on NCBI build 36), already identified as the gene responsible for Pendred syndrome in humans (Everett, et al., 1997). This gene was considered a likely candidate because a targeted disruption of Slc26a4 in mice causes a similar phenotype (Everett et al.,2001).

In order to evaluate the new mutation at the DNA level, PCR primers were designed to amplify each exon of the Slc26a4 gene, and PCR products were sequenced at The Jackson Laboratory core sequencing facility. The entire coding sequence, except for a small GC-rich region of exon 2, was then compared to the mouse sequence publicly available. A single base change from T>A was detected in exon 7 in mutant mouse DNA. This base change modifies the amino acid codon from TGT (cysteine) to TGA , a premature stop codon (fig4).

Acknowledgements

We thank Debra Thompson for identification of the original mutant mice, Jane Farley for the sperm and testis analysis, Susan Grindle for blood chemistry analysis and Chantal Longo-Guess and Heping Yu for performing the ABR.

References

Everett LA, Glaser B, Beck JC, Idol JR, Buchs A, Heyman M, Adawi F, Hazani E, Nassir E, Baxevanis AD, Sheffield VC,Green ED. Pendred syndrome is caused by mutations in a putative sulphate transporter gene (PDS). Nat Genet. 1997 Dec;17(4):411-22

Everett LA; Belyantseva IA; Noben-Trauth K; Cantos R; Chen A; Thakkar SI; Hoogstraten-Miller SL; Kachar B; Wu DK; Green ED, Targeted disruption of mouse Pds provides insight about the inner-ear defects encountered in Pendred syndrome. Hum Mol Genet 2001 Jan 15;10(2):153-6