SPATIAL DISTRIBUTIONS OF RETINOIC ACID RECEPTOR GENE TRANSCRIPTS IN THE PRENATAL MOUSE INNER-EAR

The expression patterns of the three mouse retinoic acid (RA) receptor gene isotypes (RAR alpha, RAR beta, and RAR gamma) and retinoid X rec eptor gene isotypes (RXR alpha, RXR beta, and RXR gamma) have been inv estigated by in situ hybridization analysis of their RNA transcripts i n the inner ear of mouse fetuses at 18.5 days of gestation. Two RARs ( RAR alpha and RAR gamma) and two RXRs (RXR alpha and RXR beta) present ed an almost ubiquitous transcript distribution with overlapping expre ssion in several regions of the cochlea, such as Kolliker's organ, the organ of Corti, the spiral limbus, and nervous structures. The organ of Corti showed an enhanced in situ labeling with RAR alpha and RXR be ta. By contrast, RAR beta and RXR gamma displayed more restricted expr ession patterns. RXR gamma in particular was strongly expressed in Kol liker's organ and in the spiral ganglion. This expression pattern sugg ests that RA may be involved in the differentiation of several cochlea r cell types. Moreover, the colocalization of several RAR and RXR gene transcripts suggests possible heterodimerization between these recept ors in several regions of the cochlea. (C) 1998 Wiley-Liss, Inc.