ANALYSIS OF THE MURINE HOXA-9 CDNA - AN ALTERNATIVELY SPLICED TRANSCRIPT ENCODES A TRUNCATED PROTEIN LACKING THE HOMEODOMAIN

Hoxa-9 is one of the homeo box (Hox) genes exhibiting similarity to th e Drosophila Abdominal B gene. So far, only partial nucleotide sequenc es have been reported for mouse Hoxa-9 cDNA (Rubin et al., (1987) Mol. Cell. Biol. 7, 3836-3841). Here, we have determined the nucleotide se quence of the 5'-region of mouse Hoxa-9 cDNA and its genomic structure . Mouse Hoxa-9 cDNA contains a complete ORF encoding a protein of 271 aa exhibiting 96.7% identity to its human counterpart. Interestingly, an alternatively spliced transcript (Hoxa-9T) was identified by RT-PCR . Sequence analysis revealed that 173 bp within the Hoxa-9 ORF was mis sing from the Hoxa-9T cDNA. This additional splicing would potentially result in a frameshift, leading to the production of a truncated prot ein lacking the homeobox. Northern blot analysis revealed that the pro be containing the homeodomain hybridized to two major transcripts (2.5 and 1.9 kb) in the trunk region of 12.5 dpc embryos, and adult kidney and large intestine. On the other hand, the probe containing the addi tional intron detected only 2.5 kb transcript in the same tissues, ind icating that 1.9 kb transcript corresponds to Hoxa-9T mRNA. We have al so determined the transcriptional start site of Hoxa-9T. (C) 1998 Else vier Science B.V.