title: Myogenin gene expression is not altered in the developing diaphragm of nitrofen-induced congenital diaphragmatic hernia.
abstract: OBJECTIVE
  Pleuroperitoneal folds (PPFs) represent the only source of muscle precursors cells (MPCs) in the primordial diaphragm. However, the exact pathogenesis of malformed PPFs and congenital diaphragmatic hernia (CDH) remains unclear. The muscle-specific transcription factor myogenin plays a key role during development and muscularization of the fetal diaphragm. Although myogenin knockout mice lack skeletal muscle fibers, the diaphragmatic musculature is intact without any defects. It has further been demonstrated that proliferation and differentiation of MPCs in PPFs and developing diaphragms are normal in rodent CDH models. We hypothesized that myogenin gene expression is not altered in malformed PPFs, developing diaphragms and diaphragmatic musculature in the nitrofen-induced CDH model.
  
  
  METHODS
  Pregnant rats were exposed to nitrofen or vehicle on gestational day 9 (D9). Fetuses were harvested during PPF formation (D13), diaphragmatic development (D14-15) and muscularization (D18-21). Fetal PPFs, developing diaphragms and diaphragmatic musculature were dissected and divided into nitrofen and control groups. Myogenin mRNA levels were analyzed by quantitative real-time polymerase chain reaction, while immunohistochemistry was performed to investigate myogenin protein expression and distribution.
  
  
  RESULTS
  Relative mRNA expression of myogenin was not significant different in PPFs (0.30 ± 0.09 vs. 0.48 ± 0.09; P = 0.37), developing diaphragms (1.25 ± 0.29 vs. 1.60 ± 0.32; P=0.53) and diaphragmatic musculature (1.08 ± 0.24 vs. 1.59 ± 0.20; P = 0.15) of nitrofen-exposed fetuses compared to controls. Myogenin immunoreactivity was not altered in the muscular components of malformed PPFs, developing diaphragms and diaphragmatic musculature of nitrofen-exposed fetuses compared to controls.
  
  
  CONCLUSIONS
  Myogenin gene expression is not altered in PPFs, developing diaphragms and diaphragmatic musculature in the nitrofen-induced CDH model, thus suggesting that diaphragmatic defects in this model develop independent of myogenic processes.
authors: National Children's Research Centre, Our Lady's Children's Hospital, Crumlin, Dublin 12, Ireland.
authors: Toshiaki
authors: T
authors: Takahashi
authors: Florian
authors: F
authors: Friedmacher
authors: Hiromizu
authors: H
authors: Takahashi
authors: Alejandro Daniel
authors: AD
authors: Hofmann
authors: Prem
authors: P
authors: Puri
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D003964:Diaphragm / Q000196:embryology*; D004195:Disease Models, Animal; D005260:Female; D015870:Gene Expression / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D065630:Hernias, Diaphragmatic, Congenital / Q000235:genetics*; D008168:Lung / Q000196:embryology; D018008:Myogenin / Q000235:genetics*; D010647:Phenyl Ethers; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D018008:Myogenin; D010647:Phenyl Ethers; C007350:nitrofen