Specific expression of the retinoic acid-synthesizing enzyme RALDH2 duringmouse inner ear development

Retinoid binding proteins and nuclear receptors are expressed in the develo ping mouse inner car. Here. we report that the retinaldehyde dehydrogenase 2 (Raldh2) gene, whose product is involved in the enzymatic generation of r etinoic acid (RA), exhibits a restricted expression pattern during mouse in ner ear ontogenesis. The Raldh2 gene is first expressed at embryonic day (E ) 10.5 in a V-shaped medio-dorsal region of the otocyst outer epithelium. w hich evolves as two separate domains upon otocyst morphogenesis. At E14.5, Raldh2 is expressed in two areas of the utricle epithelium and specific reg ions of the saccule and cochlear mesenchyme. Later, Raldh2 transcripts are restricted to two cochlear areas, the stria vascularis and Reissner membran e. Raldh2 mesenchymal expression did not correlate with migrating neural cr est-derived melanoblasts. These restricted expression domains may correspon d to specific sites of RA synthesis during inner ear morphogenesis. (C) 200 1 Elsevier Science Ireland Ltd. All rights reserved.