Comparative Analyses between Skeletal Muscle miRNAomes from Large White and Min Pigs Revealed MicroRNAs Associated with Postnatal Muscle Hypertrophy

<div><p>The molecular mechanism regulated by microRNAs (miRNAs) that underlies postnatal hypertrophy of skeletal muscle is complex and remains unclear. Here, the miRNAomes of <i>longissimus dorsi</i> muscle collected at five postnatal stages (60, 120, 150, 180, and 210 days after birth) from Large White (commercial breed) and Min pigs (indigenous breed of China) were analyzed by Illumina sequencing. We identified 734 miRNAs comprising 308 annotated miRNAs and 426 novel miRNAs, of which 307 could be considered pig-specific. Comparative analysis between two breeds suggested that 60 and 120 days after birth were important stages for skeletal muscle hypertrophy and intramuscular fat accumulation. A total of 263 miRNAs were significantly differentially expressed between two breeds at one or more developmental stages. In addition, the differentially expressed miRNAs between every two adjacent developmental stages in each breed were determined. Notably, ssc-miR-204 was significantly more highly expressed in Min pig skeletal muscle at all postnatal stages compared with its expression in Large White pig skeletal muscle. Based on gene ontology and KEGG pathway analyses of its predicted target genes, we concluded that ssc-miR-204 may exert an impact on postnatal hypertrophy of skeletal muscle by regulating myoblast proliferation. The results of this study will help in elucidating the mechanism underlying postnatal hypertrophy of skeletal muscle modulated by miRNAs, which could provide valuable information for improvement of pork quality and human myopathy.</p></div

Cluster analysis of miRNA libraries from skeletal muscle of Large White and Min pigs.

<p>The skeletal muscle was collected at different developmental stages. LW, Large White pig; M, Min pig.</p

Pairwise comparisons of differentially expressed (DE) miRNAs in skeletal muscle at different developmental stages.

<p>The comparisons were made for Large White and Min pigs. The numbers marked in the overlapping areas indicate the common DE miRNAs.</p

Number of known miRNAs, homologous novel miRNAs, and nonhomologous miRNAs.

<p>Number of known miRNAs, homologous novel miRNAs, and nonhomologous miRNAs.</p

Length distribution of the small RNA sequences.

<p>LW, Large White pig; M, Min pig.</p

Expression levels of miR-204 at five postnatal development stages between Large White and Min pigs.

<p>Expression levels of miR-204 at five postnatal development stages between Large White and Min pigs.</p

Overview of the small RNA sequences in the 10 libraries.

<p>Each number in the pie chart represents the percentage of reads of that category in the total small RNA sequences.</p

Differentially expressed miRNAs between every two adjacent developmental stages in Large White and Min pigs.

<p>Differentially expressed miRNAs between every two adjacent developmental stages in Large White and Min pigs.</p

Microscopic characteristics of sheep oocyte maturation stained with aceto-orcein (200× magnification).

<p>(A) Oocyte at GV stage, arrow points to germinal vesicle; (B) oocyte at GVBD stage, arrow points to condensed chromosomes; (C) oocyte at late spindle stage, arrow points to spindle fibers; and (D) oocyte at middle MII stage, arrow points to the first polar body.</p

The α-tubulin distribution around chromosomes in sheep oocytes after 22 h of <i>in vitro</i> maturation.

<p>Red indicates chromosomes and green indicates α-tubulin. (A, 10×40) Disorderly distribution of chromosomes; (B, 10×40) little α-tubulin distributed around chromosomes; (C,10×20) nearly no α-tubulin distributed around chromosomes; (D, 10×40) α-tubulin distributed on a spindle; and (E, F, 10×40) formation of microtubules and extrusion of polar bodies at meiosis II.</p