Differential expression of LIM domain-only (LMO) genes in the developing mouse inner ear

The vertebrate inner ear, a complex sensory organ with vestibular and auditory functions, is derived from a single ectoderm structure called the otic placode. Currently, the molecular mechanisms governing the differentiation and specification of the otic epithelium are poorly understood. We present here a detailed expression study of LMO1-4 in the developing mouse inner ear using a combination of in situ hybridization and immunohistochemistry. LMO1 is specifically expressed in the vestibular and cochlear hair cells as well as the vestibular ganglia of the developing inner ear. LMO2 expression is detected in the periotic mesenchyme of the developing mouse cochlea from E12.5 to E14.5. The expression of LMO3 expression is first observed in the cochlea at E13.5 and becomes confined to the lesser epithelial ridge (LER) from E14.5 to E17.5. LMO3 is also expressed in some of the vestibular ganglion cells. LMO4 is initially expressed in the dorsolateral portion of the otic vesicle and its expression persists in the semicircular canals, macula, crista, and the spiral ganglia throughout embryogenesis. Thus, the regionalized expression patterns of LMO1-4 are closely associated with the morphogenesis of the inner ear.