Zebrafish Lmx1b.1 and Lmx1b.2 are required for maintenance of the isthmic organizer.

The mesencephalic and metencephalic region (MMR) of the vertebrate central nervous system develops in response to signals produced by the isthmic organizer (IsO). We have previously reported that the LIM homeobox transcription factor Lmx1b is expressed within the chick IsO, where it is sufficient to maintain expression of the secreted factor wnt1. In this paper, we show that zebrafish express two Lmx1b orthologs, lmx1b.

cBlimp-1 expression in chick limb bud development.

Blimp is a transcriptional repressor that has been identified in humans, mice and frogs. Here, we describe the cloning of the gene that encodes for the chick homolog of Blimp, cBlimp-1, and the tempo-spatial expression pattern of cBlimp-1, during chick development. cBlimp-1 whose gene product shares a high level of identity with its homologs from other organisms, was found to be expressed in the apical ectodermal ridge and posterior dorsal ectoderm of developing limb buds.