title: The Krox-20 null mutation differentially affects the development of masticatory muscles.
abstract: The Krox-20 null mutation results in a loss of rhombomeres 3 and 5, which give rise to neurons that are essential to oral motor behaviors. Thus, the Krox-20 null mutant is an excellent model to investigate the development of oral motor circuitry. Our morphological examination of embryonic and neonatal Krox-20 null mutants revealed that a significant reduction of anterior digastric and mylohyoid muscles, the primary jaw openers, occurs between embryonic days 15 and 19. There are no gross morphological alterations in other masticatory muscles. These findings demonstrate that Krox-20 expression is critical for the normal development of the primary jaw opener musculature and they help explain previous studies documenting a reduction in jaw opening in Krox-20 null mutants. Since jaw opening is the power stroke of suckling behavior, our data help explain the reduction of colostrum/milk ingestion in Krox-20 null mutant neonates.
authors.affiliation: Department of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, Calif. 90089, USA. turman@hsc.usc.edu
authors.forename: J E
authors.initials: JE
authors.lastname: Turman
authors.forename: N B
authors.initials: NB
authors.lastname: Chopiuk
authors.forename: C F
authors.initials: CF
authors.lastname: Shuler
mesh_terms: D000818:Animals; D000833:Animals, Suckling; D001284:Atrophy; D004268:DNA-Binding Proteins / Q000235:genetics*; D051767:Early Growth Response Protein 2; D005260:Female; D008297:Male; D008410:Masticatory Muscles / Q000196:embryology* / Q000294:innervation / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009046:Motor Neurons / Q000166:cytology; D009154:Mutation; D011247:Pregnancy; D013391:Sucking Behavior; D014157:Transcription Factors / Q000235:genetics*; D014276:Trigeminal Nerve / Q000166:cytology / Q000196:embryology; D014278:Trigeminal Nuclei / Q000166:cytology / Q000196:embryology
chemical_list: D004268:DNA-Binding Proteins; D051767:Early Growth Response Protein 2; C497327:Egr2 protein, mouse; D014157:Transcription Factors