Worm Breeder's Gazette 11(5): 41
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
myo-2 encodes a myosin heavy chain isoform expressed specifically in pharyngeal muscles. We have been analyzing myo-2 regulatory regions using lacZ fusions. Our experiments have been done by examining -gal expression in L3-adult F1 progeny of injected hermaphrodites. We have identified an enhancer in a 227bp EcoRI-RsaI fragment located about 670bp upstream of the myo-2 translational start site ( ATG). When inserted upstream of a glp-1/lacZ fusion, this enhancer induces -gal activity almost exclusively in the pharyngeal muscles (a small number of animals (<4%) also express -gal in 1-3 large nuclei near the anus; we have not characterized these cells further). The glp-1/lacZ fusion alone is not expressed. Therefore, the myo-2 enhancer appears almost completely specific for pharyngeal muscles. Consistent with this result, both myo-3/lacZ and CeMyoD/lacZ fusions, which are normally active only in body wall muscle, are expressed in pharyngeal and body wall muscles when placed downstream of the myo-2 enhancer. myo-2/lacZ fusions lacking the enhancer are also expressed in pharyngeal muscle. Thus, there are at least two independent pharyngeal specific regulatory elements upstream of myo-2. This downstream element has been localized to 250bp NarI-PvuI fragment just 5' to the ATG translational initiation codon. It does not act as an independent pharyngeal enhancer when inserted upstream of the myo-3 promoter. Rather, this element behaves as a pharyngeal muscle specific promoter. myo-2 regulation is analogous to that of unc-54 (Fire and Harrison, WBG11,2,p.22). In that case, a body wall specific element just upstream of the promoter acts only very weakly as an enhancer, while an internal element 1kb downstream acts independently as a strong body wall muscle specific enhancer. We are currently defining the pharyngeal muscle regulatory sequences more precisely and plan to identify trans-acting factors interacting with them. [See Figure 1]