Fig 1.
Muscles Selected for Analysis of Young Mice.
A) Genioglossus (GG), Styloglossus (SG), Anterior belly of the digastric (ADG), and Posterior belly of the digastric (PDG) were selected from young mice for analysis of MyHC isoform composition. B) Representative SDS-PAGE gel excerpts. 2a/2x = position of myosin heavy chains 2a and 2x. 2b = myosin heavy chain 2b. I = myosin heavy chain I. C) Relative levels of the MyHC 2b isoform protein in each muscle, compared by genotype. Mean and SEM. (* indicates p ≤ .05).
Fig 2.
Developmental trajectory of MyHC 2b protein levels in digastric muscles of Ts65Dn assessed by SDS-PAGE.
A) SDS-PAGE gels comparing Ts65Dn of different stages of postnatal development to age-matched euploid controls. 2a/2x = position of myosin heavy chains 2a and 2x. nn = neonatal myosin heavy chain isoform. 2b = myosin heavy chain 2b. I = myosin heavy chain I. B) Relative MyHC 2b isoform protein percentages in digastric muscle samples of different age groups. ** indicates p ≤ .01. Mean and SEM. n = 5–7 (p11), n = 7–9 (5–6 weeks).
Fig 3.
Immunofluorescence staining of thin sections.
A) Anterior (ADG) and posterior (PDG) digastric muscle cross sections. Photomontage borders are indicated in white. MyHC 2b (Red), Laminin (Green), Nuclei (Blue). Scale: 200 μm. B) Percentage of myofibers staining positive for MyHC 2b. n = 5–7 per group. Mean and SEM. C) Cross-sectional area of myofibers. n = 4–6 per group. Mean and SEM D) Percentage of myofibers positive for centralized nuclei. n = 6–7 per group. Mean and SEM.
Fig 4.
Behavioral Feeding and Swallowing Assays of Young Mice: A) Videofluoroscopy swallow study stills with black arrows indicating the food bolus at the valleculae in the frame immediately prior to a swallow (left), and a subsequent frame showing the bolus in the esophagus (right). B) Left panel: Videofluoroscopic swallow study (VFSS) analysis of a cheese puree, showing the number of swallows per 2-second intervals. Means and SEM. Right Panel: Inter-swallow Intervals, measured in seconds, quantified from the same studies. Means and SEM. C) Mastication rate during feeding on a hard food pellet, assessed by videorecording.
Fig 5.
MyHC 2b gene and protein expression in adult mice.
qRT-PCR analysis of MyHC isoform expression in A) Anterior Digastric (ADG) muscle, and B) Posterior Digastric (PDG) muscle of 10–11 wk old Ts65Dn as compared to euploid sibling controls. MyHC 2b (n = 4 per group), MyHC 2x/d (n = 3 per group), MyHC 2a (n = 4 per group). * indicates p ≤ .05. Bars show mean and SEM. C) Relative amounts of MyHC 2b protein in the ADG of adult mice shown by weeks of age. D) Relative amounts of MyHC 2b protein in the PDG of adult mice shown by weeks of age.