Effects of maternal hyperthermia on myogenesis-related factors in developing upper limb.
BACKGROUND
Maternal hyperthermia is one causative factor in various congenital anomalies in experimental animals and humans. In the present study, we assessed the effects of high temperature on limb myogenesis in mice.


METHODS
Pregnant mice, C57BL/6 strain, were exposed to hyperthermia (43 degrees C, 5 minutes) on embryonic day (ED) 8. Fetuses on ED 11, 13, 15, and 17 and neonates on postnatal day (PD) 1 were collected. To characterize the effects of hyperthermia on myogenesis-related factors Pax3, MyoD, myogenin, and myosin heavy chain (MyHC) during skeletal muscle development, we performed RT-PCR, western blotting, immunohistochemistry, and transmission electron microscopy.


RESULTS
Pax3 gene expression was still detected on ED 13 in hyperthermia-exposed fetuses. The expression of MyoD protein was down-regulated in fetuses exposed to hyperthermia. In contrast, myogenin and MyHC protein expression were up-regulated on PD 1 and ED 17, respectively, in the group exposed to hyperthermia. Immunohistochemical analysis confirmed the findings from western blot analysis. Compared with control neonates, a TEM study revealed immature muscle fibers in PD 1 hyperthermia neonates. Thus, our studies showed that maternal hyperthermia induced delayed expression of Pax3 and inhibited expression of MyoD proteins, which are known to play important roles in migration of myogenic progenitor cells, and in myoblast proliferation. In addition, maternal hyperthermia also delayed the expression of myogenin protein for the formation of myotubes, and MyHC protein, which is one of the final muscle differentiation factors.


CONCLUSIONS
Our data suggest that maternal hyperthermia delays limb myogenesis in part by disregulating the expression of key myogenesis-related factors.
Lee
Jin
J
Department of Anatomy and Cell Biology, College of Medicine, Hanyang University, Seoul, Korea.
Mirkes
Philip E
PE
Paik
Doo Jin
DJ
Kim
Won Kyu
WK
D000818:Animals; D004622:Embryo, Mammalian / Q000378:metabolism; D005260:Female; D005334:Fever / Q000378:metabolism*; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D046529:Microscopy, Electron, Transmission; D024510:Muscle Development / Q000502:physiology*; D017570:MyoD Protein / Q000378:metabolism; D018008:Myogenin / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000378:metabolism; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors / Q000235:genetics / Q000378:metabolism; D011247:Pregnancy; D034941:Upper Extremity / Q000196:embryology* / Q000502:physiology
D017570:MyoD Protein; C057363:MyoD1 myogenic differentiation protein; C503801:Myog protein, mouse; D018008:Myogenin; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors; C068686:Pax3 protein, mouse; D018995:Myosin Heavy Chains