DECORIN AND COLLAGEN TYPE-I GENE-EXPRESSION IN AVIAN LOW SCORE NORMALPECTORAL MUSCLE

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.