Fig. 1. Brain expresses a headless form of Myo10. (A) Schematic map of the human Myo10 gene and bar diagrams of the full-length and headless Myo10 transcripts. The headless transcript begins with an alternate exon (gray) that encodes a 5' UTR specific to headless Myo10. Splicing of this 5' UTR to the exon that begins at M₆₄₄ of full-length Myo10, results in a headless transcript lacking the first 643 aa of full-length Myo10. Major domains of the Myo10 protein are indicated by colored boxes, vertical lines on the gene map represent exons. The horizontal red lines indicate the locations of the probes used for northern blotting. (B) Multiple-tissue northern blot incubated with three different Myo10 probes. The blot was originally incubated with a probe targeting the 3' UTR common to both transcripts (right) and detected both a 9 kb band (upper arrowhead) in non-brain tissues and a smaller 7 kb band (lower arrowhead) in brain (Berg et al., 2000). The blot was then stripped and reprobed with a sequence from the 5' UTR of the headless transcript (middle), which detected a 7 kb band in brain but not the full-length 9 kb band in other tissues. The blot was then stripped and reprobed a final time with a sequence from the head domain (left). In addition to the 7 kb band in brain, the headless probe appears to react non-specifically with a faint band in tissues such as liver that is slightly larger than the 9 kb band corresponding to full-length Myo10. (C) Sequence alignment of human EST AI878891 with full-length Myo10 cDNA (NM_012334) show the 5' UTR specific to the headless form (capitalized nucleotides) as well as the initial protein-coding exons of the headless form and their perfect match to the full-length Myo10 exon beginning at M₆₄₄. Exon boundaries are indicated by vertical dotted lines and stop codons in the alternate 5' UTR are highlighted in red. Predicted start methionines at M₆₄₄ and M₇₄₇ are shown in green.