Disease relevance of Herculin

• When expressed under the control of the simian virus 40 early promoter, transfected herculin renders murine NIH 3T3 and C3H/10T1/2 fibroblasts myogenic [1].

High impact information on Herculin

• The spatial and temporal expression pattern of the muscle regulatory gene Myf-6 (MRF4/herculin) has been investigated by in situ hybridization during embryonic and fetal mouse development [2].
• All of these affect the expression of myogenin, one of the recently discovered family of myogenesis controlling genes, and FGF and TGF-beta have been shown to inhibit the expression of MyoD1 (and probably myf-5 and herculin) as well [3].
• In doing so, it also activates expression of myogenin, MyoD, and endogenous herculin in NIH 3T3 recipients [1].
• The herculin gene is physically linked to the Myf-5 gene on the chromosome; only 8.5 kilobases separate their translational start sites [1].
• In adult mice, herculin is expressed in skeletal muscle but is absent from smooth muscle, cardiac muscle, and all nonmuscle tissues assayed [1].

Biological context of Herculin

• A putative 27-kDa protein is encoded by three exons contained within a 1.7-kilobase fragment of the herculin gene [1].
• In this work, we have initiated studies to identify DNA sequences that govern Myf-5 and MRF4 (herculin, myf-6) transcription [4].
• Myogenin gene activity declined rapidly (t1/2: approximately 2 min), comparable to the rate of acetylcholine receptor (AChR) gene inactivation, while other myogenic bHLH genes either lost activity more slowly (MyoD) or not at all (myf5, herculin) [5].

Anatomical context of Herculin

• On myotube formation, herculin reaches high levels; concomitantly, the epsilon subunit gene becomes a common MDF target and begins to be expressed [6].
• Using a ribonuclease protection assay, we found that exponentially growing RMo myoblasts contained no detectable myogenin or herculin mRNA, while differentiating myoblasts contained high levels of myogenin mRNA but no herculin mRNA [7].

Gene context of Herculin

• 2. Upon denervation, herculin mRNA remains essentially unchanged, myf5 transcript levels approximately double, and MyoD message is up-regulated by two- to fivefold [8].
• 1. We have prepared probes specific for the chicken myogenic determination genes MyoD, myogenin, myf5, and herculin and have investigated the expression of these genes in response to denervation and acute electrical stimulation in neonate chick muscle, using ribonuclease protection [8].
• RESULTS: The MCs in newborn mice possessed Id but did not express either protein herculin or myoD [9].
• Four members, MyoD, myogenin, myf5 and MRF4/herculin/myf6, have been identified in higher vertebrates and have been shown to exhibit distinct but overlapping functions [10].

References