Semester

Summer

Date of Graduation

2001

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

John Killefer.

Abstract

Reverse-transcription polymerase chain reaction (RT-PCR) was performed to measure myostatin, follistatin, activin-B gene expressions during chicken embryonic development. Strong myostatin expression was found in the early chicken embryos (E 0, E 1) and the developmental expression pattern of myostatin mRNA coincided with the periods of primary and secondary muscle fiber formation. Follistatin transcripts followed a linear expression pattern from E 0 to E 20, while activin-B had a quadratic pattern. The ontogeny of myostatin gene expression was nearly identical in satellite cells isolated from pectoralis major (PM) and biceps femoris (BF) muscles of chicken. Activin-B mRNA level in PM satellite cells was higher than in BF satellite cells at 72 h and 120 h (P < 0.01). IGF-II mRNA level plateaued in PM satellite cells by 48 h after plating (P < 0.05), and remained elevated until 144 h of culture. In ovo administration of rhIGF-I at E 3 shifted myostatin, follistatin, activin-B, and TGF-(32 gene expressions during chicken embryonic development. For example, myostatin mRNA from pectoralis muscles of rhIGF-I injected embryos increased on E 10 (∼2.5 fold) and remained high through E 13, whereas mRNA from control pectoralis muscles increased at E 9 and remained high until E 12. IGF-I, -II and IGF receptor-I mRNA and protein levels were determined in a wide variety of myostatin knockout mice tissues. IGF-I mRNA levels were not different between control and knockout mice tissues, whereas levels for IGF-II were significantly higher in myostatin knockout mice kidney and soleus muscles than that of control mice (P < 0.01). IGF-Receptor-I mRNA levels from control mice heart (P < 0.05) and kidney (P < 0.01) were significantly higher than that of myostatin knockout mice, while levels were lower in control mice pectoralis muscle than that of knockout mice (P < 0.01). The strongly IGF-II positive cells were more common in myostatin knockout mice and were seen in a few foci in control mice, while no consistent differences in IGF-II immunoreactivity were detected between the two groups of mice kidneys.

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