The avian Low Score Normal (LSN) genetic muscle weakness is phenotypic
ally characterized by a reduction in the ability of the birds to right
themselves from a supine position. Compared to normal skeletal muscle
, LSN muscle has normal myosin isoform switching and cell-cell recogni
tion, elevated glycosaminoglycan and decorin levels at embryonic Day 2
0, and a large increase in collagen crosslinking at 6 wk posthatch. To
begin to determine the biological mechanism involved in the elevated
decorin protein concentration at embryonic Day 20, the steady-state le
vels of transcripts encoding both decorin and collagen Type I at embry
onic Days 14, 19, and 20, and at 1 d and 6 wk posthatch were measured.
On embryonic Day 20, collagen Type I transcripts were not different f
rom the control but there was a significant elevation in decorin trans
cript levels. At 1 d and 6 wk posthatch, transcript levels of decorin
and collagen Type I were not different between LSN and controls. The c
hange in decorin transcript steady-state levels is limited to late emb
ryonic development and suggests an alteration in a signal transduction
pathway regulating decorin transcription.