EXPRESSION PATTERN OF THE MURINE LIM CLASS HOMEOBOX GENE LHX3 IN SUBSETS OF NEURAL AND NEUROENDOCRINE TISSUES

Murine Lhx3 cDNA isolated from the mouse pituitary cDNA Library encode s a LIM-type homeodomain protein that contains two tandemly repeated L IM domains and the homeodomain, The identities of predicted amino acid sequences between the mouse Lhx3 and Xenopus Xlim-3 genes are 80, 95, and 97% in the LIM domains 1 and 2, and the homeodomain, respectively , and 84% in the entire protein, 5'-RACE procedures and genomic clonin g revealed that two distinct N-terminal sequences arise from. two diff erent exons la and Ib, Exon 1a encodes a sequence similar to that of X lim-3, whereas exon 1b encodes a different N-terminus. It is likely th at there are two transcription initiation sites in the Lhx3 gene. The Lhx3 transcripts were detected by whole mount in situ hybridization as early as day E9.5 post coitum in Rathke's pouch and the dosing neural tube. During subsequent development, Lhx3 expression was observed in the anterior and intermediate but not in the posterior lobes of the pi tuitary, and in the ventral hindbrain and spinal cord. Northern blot a nalysis of adult tissues showed that Lhx3 mRNA persists in the pituita ry. The expression pattern of Lhx3 is well conserved between Xenopus a nd mouse, underscoring the functional importance of this gene as a reg ulator of development. A number of established cell lines of pituitary origin express Lhx3 and therefore constitute a useful tool for furthe r study of Lhx3 gene function. (C) 1995 Wiley-Liss, Inc.