Genomic organization and neonatal expression of the bovine myostatin gene

Myostatin belongs to the Transforming Growth Factor-beta (TGF-beta) superfa mily and is expressed in developing and mature skeletal muscle. Biologicall y, the role of myostatin seems to be extremely well conserved during evolut ion since inactivating mutations in myostatin gene cause similar phenotype of heavy muscling in both mice and cattle. In this report we have analysed the genomic structure and neonatal expression of the bovine myostatin gene. The molecular analysis shows that the bovine myostatin gene consists of th ree exons and two introns. The sizes of the first and second exons are 506 and 374 base pairs (bp) respectively. The size of the third exon was found to be variable in length (1701 or 1812 or 1887 nucleotides), whereas the si ze of the two introns is 1840 and 2033 bps. In the first exon of bovine myo statin, a single transcription initiation site is found at 133 bps from the translation start codon ATG. Sequencing the 3' untranslated region indicat ed that there are multiple polyadenylation signals at 1301, 1401 and 1477 b p downstream from the translation stop codon (TGA). Furthermore, 3' RACE an alysis confirmed that all three polyadenylation sites are used in vivo. Usi ng quantitative RT-PCR we have analysed neonatal expression of myostatin ge ne. In both the M. biceps femoris and M. semitendinosus, the highest level of myostatin expression was observed on day 1 postnatally, then gradually r educed on days 8 and 14 postnatally. In contrast, in the M. gastrocnemius, myostatin expression was highest on day 14 and lowest on day 8. These resul ts indicate that myostatin gene structure and function is well conserved du ring evolution and that neonatal expression of myostatin in a number of pre dominantly fast twitch muscles is differentially regulated.