MYOSTATIN EXPRESSION IN PORCINE TISSUES - TISSUE-SPECIFICITY AND DEVELOPMENTAL AND POSTNATAL REGULATION

The objective of this study was to establish the developmental pattern and tissue specificity of porcine myostatin expression and to evaluat e expression in skeletal muscle during circumstances in which muscle g rowth was altered. Northern blot analysis revealed two transcripts (1. 5 and 0.8 kb). Myostatin mRNA was detected in whole fetuses at 21 and 35 days and was markedly increased (P < 0.05) by 49 days. At birth, mR NA abundance in longissimus muscle had declined significantly (P < 0.0 5) from that at day 105 of gestation and continued to decrease (P < 0. 05) to its lowest level 2 wk postnatally (4 kg body wt). Myostatin exp ression was higher (P < 0.05) at 55, 107, and 162 kg body wt than at 4 kg body wt. Postnatally, myostatin mRNA was detected in skeletal musc le and mammary gland. Expression at birth was 65% higher (P < 0.04) in longissimus muscle of low-birth-weight piglets (0.57 +/- 0.052 kg bod y wt) vs, normal (1.37 +/- 0.077 kg body wt) littermates, irrespective of gender. However, suppression of longissimus muscle growth by food deprivation (3 days) did not alter (P > 0.15) myostatin expression in either 4- or 7-wk-old piglets. Additionally, myostatin mRNA abundance was not changed by porcine growth hormone administration in growing an imals. These data indicate that myostatin expression in skeletal muscl e peaks prenatally and that greater expression is associated with low birth weight. Expression in mammary gland indicates a possible role fo r myostatin in mammary gland development and/or lactation.