A CONSERVED FAMILY OF ELAV-LIKE GENES IN VERTEBRATES

A large family of genes encodes proteins with RNA recognition motifs t hat are presumed to bind RNA and to function in posttranscriptional re gulation. Neural-specific members of this family include elav, a gene required for correct differentiation and maintenance of neurons in Dro sophila melanogaster, and a related gene, HuD, which is expressed in h uman neuronal cells. I have identified genes related to elav and HuD i n Xenopus laevis, zebrafish, and mouse that define a family of four cl osely related vertebrate elav-like genes (elrA, elrB, elrC, and elrD) in fish, frogs, and mammals. In addition to protein sequence conservat ion, a segment of the 3'-untranslated sequence of elrD is also conserv ed, implying a functional role in elrD expression. In adult frogs, elr C and elrD are exclusively expressed in the brain, whereas elrB is exp ressed in brain, testis, and ovary, During Xenopus development, elrC a nd elrD RNAs are detected by late gastrula and late neurula stages, re spectively, whereas a nervous system-specific elrB RNA species is expr essed by early tadpole stage. Additional elrB transcripts are detected in the ovary and early embryo, demonstrating a maternal supply of mRN A and possibly of protein These expression patterns suggest a role for different elav-like genes in early development and neuronal different iation. Surprisingly, elrA is expressed in all adult tissues tested an d at all times during development. Thus, the widely expressed elrA is expected to have a related function in ail cells.