Figure 1. Retrovirus-mediated lineage analysis of the E11.5 mouse inner ear.

A, schematic of the proviral form of the replication defective BOLAP murine retrovirus. PLAP is the genetically encoded lineage label. The 24-bp oligonucleotide library consists of approximately10⁷ unique 24-bp sequence tags. Abbreviations: LTR, long terminal repeat; neo, TnS neomycin resistance gene; SV40, simian virus 40 polyadenylation signal. B, lateral view of an E11.5 mouse embryo whose left otic vesicle was filled by transuterine microinjection with dye-tinged retroviral inoculum. The endolymphatic duct (ed) and cochlear duct (cd) are evident. Abbreviations: 4^th, nascent 4^th ventricle of the hindbrain; fb, forebrain; lb, limb bud; mb, midbrain. C, schematic of the P6 mouse inner ear showing the approximate locations of the sensory organs in gray. Abbreviations: A, anterior; asc, anterior semicircular canal; c, crista ampularis; D, dorsal; es, endolymphatic sac; m, maculae; oC, organ of Corti; psc, posterior semicircular canal; s, saccule; u, utricle. D–F, analysis of a clone. D (left), a confocal image of a control P6 posterior crista demonstrating sensory hair cells (myosin7a [Myo7A], green), filamentous actin (F-actin; phalloidin, red), and cell nuclei (DAPI, blue). The white line demarcates the boundary between the sensory epithelium and the underlying mesenchyme (left). The white arrow indicates the position of the neural crest-derived melanin-expressing cells most proximal to the sensory epithelium of the crista (bright field image not shown). D, (right), PLAP-positive cells detected in a P6 posterior crista. The black line demarcates the sensory/nonsensory boundary. The black arrow indicates the position of the neural crest-derived melanin-expressing cells most proximal to the sensory epithelium. The larger purple cell (large red oval) is in the hair cell region. The small purple cell (small red oval) is in the supporting cell layer. The blue oval is a negative control pick. E, enlarged images of the hair cell and supporting cell outlined in D (right). F, sequence of the 24-bp oligonucleotide tags amplified from the hair cell (Pick 1) and supporting cell (Pick 2). The hair cell and supporting cell in the posterior crista share the same sequence tag suggesting they originated from a common progenitor and are lineally related.