Alternative transcripts expressed by small bristles, the Drosophila melanogaster nxf1 gene.

The tissue-specific accumulation of small bristles (Dm nxf1) transcripts at different developmental stages of Drosophila melanogaster was analyzed by Northern blots and RT PCR. We identified four distinct transcripts: ubiquitous (3.5kb); ovary and early embryo specific (3.3kb); testis specific (1.9kb and 2.8kb) and nervous system specific (5.1kb). The pattern of Dm nxf1 gene expression in ovaries and early embryos (0-2h) is similar: the sizes of transcripts range from 3.0 to 3.5kb. We propose that this size variability may reflect the different extent of cytoplasmic polyadenylation. In testes, the 2.8-kb transcript originates from alternative termination of transcription and the 1.9-kb transcript is supposed to originate from an alternative transcription start. During ontogenesis, the 5.1-kb transcript can be clearly detected in 10- to 18-h-old embryos, most prominently in the nervous ganglia of larvae, and it represents a major species in imago head extracts. We found that the 5.1-kb transcript, similarly to the nxf1 heavy transcripts in Homo sapiens and Mus musculus, results from the retention of intron 5-6 that corresponds to the intron 10-11 in Hs nxf1 and Mm nxf1 genes.