Cloning, characterization, and mRNA expression analysis of novel human fetal cochlear cDNAs.

To identify novel genes that are expressed specifically or preferentially in the cochlea, we constructed a cDNA library enriched for human cochlear cDNAs using a suppression subtractive hybridization technique. We analyzed 2640 clones by sequencing and BLAST similarity searches. One hundred and fifty-five different cDNA fragments mapped in nonsyndromic hearing impairment loci for which the causative gene has not been cloned yet. Approximately 30% of the clones show no similarity to any known human gene or expressed sequence tag (EST). Clones mapping in nonsyndromic deafness loci and a selection of clones that represent novel ESTs were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR) of RNA derived from 12 human fetal tissues. Our data suggest that a quarter of the novel genes in our library are preferentially expressed in fetal cochlea. These may play a physiologically important role in the hearing process and represent candidate genes for hereditary hearing impairment.