Fractional rates of muscle protein synthesis and degradation in chickens with genetic muscular dystrophy

Comparison of proteolytic-related gene expression in the skeletal muscles of layer and broiler chickens

Previous studies have shown that the muscle protein degradation rates of broiler are lower than those of layer chickens. In this study, we assessed proteolytic-related gene expression in the pectoralis muscle of layer and broiler chickens. The mRNA levels of atrogin-1/MAFbx and proteasome C2 subunit, but not those of ubiquitin, m-calpain large subunit, cathepsin B, or caspase-3, were lower in the skeletal muscle of the broilers than in the layers at 7 and 14 d of age. We infer that the lower muscle protein degradation of broilers than of layers at least partly relates to lower mRNA expression of atrogin-1/MAFbx and proteasome C2 subunit in the skeletal muscle of broilers.

Localization of the muscular dystrophy AM locus using a chicken linkage map constructed with the Kobe University resource family

A chicken linkage map, constructed with the Kobe University (KU) resource family, was used to locate the genetic locus for muscular dystrophy of abnormal muscle type (AM). The KU resource family is a backcross pedigree with 55 offspring produced from the mating of a White Leghorn F-line (WL-F) male and a hybrid female produced from a cross between the WL-F male and a female of the Fayoumi OPN line who was homozygous for the AM gene. In total, 872 loci were genotyped on the pedigree; 749 (86%) were informative and mapped to 38 linkage groups. These informative loci included 649 AFLPs, 93 MS, three functional genes, the AM locus, sex phenotype, and two red blood cell loci. The remaining 123 markers were unlinked. Nineteen of the 38 KU linkage groups were assigned to macrochromosomes 1-8 and 11 microchromosomes including chromosome W, while 19 linkage groups were unassigned. The total map was 3569 cM in length, with an average marker interval of 4.8 cM. The AM locus was mapped 130 cM from the distal end of chromosome 2q.

Variation among lines selected for body size in the fractional rate of degradation of protein and acid protease activity in the muscle of quail (Coturnix coturnix japonica)

Fractional rates (%/day) of degradation of muscle protein were determined by measuring the output of NT-methylhistidine (NT-MH) in the excreta at 2 and 10 weeks of age in three lines of quail, a random-bred line and two lines selected for body size, one for increased and the other for decreased size. In all lines, fractional rates of degradation of muscle protein at 2 weeks of age were higher than those at 10 weeks of age. The fractional rate of degradation at 2 weeks of age was highest for the RR line, 9.1-9.2%/day. However, at 10 weeks of age, the rank order changed, and the RR line showed the lowest rate, 1.8-1.9%/day. The SS line (5.8-6.2%/day at 2 weeks and 5.8-5.9%/day at 10 weeks of age) was significantly higher than the LL line (4.1-4.2%/day at 2 weeks and 2.1-2.2%/day at 10 weeks of age). Acid protease activities in supernatants of homogenized muscle of the three lines of quail at 2 and 10 weeks of age were measured. In all lines, the acid protease activities in supernatant of homogenized muscle decreased from 2 to 10 weeks of age. At 2 weeks, the protease activity of the RR line was significantly higher than that of the LL and SS lines, which did not differ significantly. However, at 10 weeks of age, the SS line had higher activity in both sexes than the LL and RR lines. The results suggest that selection for body size brings about significant changes in both fractional degradation rate and acid protease activity in the muscle.