[Evidence of a novel gene for the LAV-syndrome].
BACKGROUND
Both LAV- (large or enlarged vestibular aqueduct) and Pendred-syndrome are autosomal recessive diseases. In contrast to Pendred-syndrome, LAV-syndrome is characterised only by an enlarged vestibular aqueduct. Pendred-syndrome is a more complex disease. Classically it is characterised by sensorineural hearing loss and enlargement of the thyroid gland. Up to now, only mutations in SLC26A4 gene are known as being responsible for both syndromes. The gene for Pendred-syndrome (SLC26A4) has been localised by linkage analysis of chromosome 7q31. This protein is expressed in the inner ear, thyroid gland, kidney, and placenta. Functional analysis of the gene product (pendrin) in Xenopus laevis oocytes revealed that pendrin acts as an iodide/chloride and chloride/formate exchanger.


METHODS
Each of the exons and flanking splice regions of the SLC26A4 gene were analysed by direct sequencing. Haplotype analysis was undertaken with microsatellite markers spanning a 5 Mbp area around the localisation of the SLC26A4 gene.


RESULTS
In sequence analysis of 42 patients with bilateral enlargement of the vestibular aqueduct, no mutation could be identified in 30 % of cases. In some of these cases, a linkage to the gene localisation on chromosome 7q31 could not be detected.


CONCLUSIONS
Our results indicate evidence for a second gene involved in the development of LAV-syndrome.
Birkenhäger
R
R
Universitätsklinik für Hals-, Nasen- und Ohrenheilkunde und Poliklinik, Universitätsklinikum Freiburg, Killianstrasse 5, D-79105 Freiburg. birkenhaeger@hno.ukl.uni-freiburg.de
Zimmer
A J
AJ
Maier
W
W
Klenzner
T
T
Aschendorff
A
A
Schipper
J
J
D000293:Adolescent; D002648:Child; D002869:Chromosome Aberrations; D002874:Chromosome Mapping; D002897:Chromosomes, Human, Pair 7; D004252:DNA Mutational Analysis; D003638:Deafness / Q000000981:diagnostic imaging / Q000235:genetics*; D005091:Exons; D005786:Gene Expression Regulation / Q000502:physiology; D005808:Genes, Recessive; D006239:Haplotypes; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics*; D018895:Microsatellite Repeats; D010375:Pedigree; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D000076988:Sulfate Transporters; D014057:Tomography, X-Ray Computed; D014723:Vestibular Aqueduct / Q000002:abnormalities* / Q000000981:diagnostic imaging; D015837:Vestibular Diseases / Q000000981:diagnostic imaging / Q000235:genetics*
D026901:Membrane Transport Proteins; C085609:SLC26A4 protein, human; D000076988:Sulfate Transporters