We present over all views how muscle genes express during muscle development in the worm. Especially results are described on the transcription factors controlling the tropomyosin gene,
tmy-1/lev-11 in pharynx and intestine and CeMyoD gene,
hlh-1 in body wall. The single tropomyosin gene of C. elegans,
tmy-1/lev-11 produces four isoforms of protein: two body wall types from the external promoter and two pharynx types from the internal promoter. The internal promoter of tropomyosin regulates expression of
tmy-1 in the pharynx and intestine. By promoter deletion of
tmy-1 reporters, a 100 bp fragment was identified that contained binding sequences for a GATA factor, for a chicken CdxA homolog and for a forkhead factor. Both the forkhead and CdxA binding sequences contributed to pharyngeal and intestinal expression. In addition, the GATA site also influenced intestinal expression of
tmy-1 reporter. We showed that ELT-2 and PHA-4 proteins interact directly with the GATA and forkhead binding sequences, respectively, in gel mobility shift assays. RNAi knockdown of
elt-2 diminished
tmy-1::gfp expression in the intestine. In contrast to RNAi knockdown of
pha-4, expression of
tmy-1::gfp in
pha-4;
smg-1 mutants was slightly weaker to that of the wild type. Ectopic expression of PHA-4 and ELT-2 by heat shock were sufficient to elicit widespread expression of
tmy1::lacZ reporter in embryos. We present models by which ELT-2, PHA-4 and CdxA control expression from the internal promoter oftmy-1 in intestine and pharynx. Combination of two of three factors controlled tissue-specific expression of the
tmy-1 gene. We found that the essential promoter sequence of the body wall troponin C gene,
pat-10/tnc-1 was similar to one of three enhancers of CeMyoD gene,
hlh-1. We have isolated three
hlh-1 enhancer binding proteins including CeMyoD. Other two are CeTIS11, one of Zn finger protein and a NHR family protein. A NHR family protein also has a binding site of the second intron of
pat-10/tnc-1. This is the reason that NHR stimulates the expression of muscle genes. Interestingly ZYX-1 bound enhancer-binding proteins CeMyoD and CeTIS-11, and also affected muscle gene expressions. ZYX-1 consists N-terminal proline rich and C-terminal three LIM domains. We will present a model on how these enhancer-binding proteins control body wall muscle gene expressions and orchestrate appropriate number and correct stage of muscle proteins.These regulation mechanisms will help to understand how muscle genes are expressed under the control of transcription factors and chemicals.