Potential regulatory role of microRNAs in the development of bovine gastrointestinal tract during early life

Purpose: The aims of this study were to profile miRNAs throughout the GIT during the early life of dairy calves and to investigate their potential regulatory roles in the development of bovine GIT. Results: The expression of miR-143 was abundant in all three gut regions and under all the time points and it targets genes involved primarily in the proliferation of connective tissue cells and muscle cells, suggesting its association with rapid tissue development during the early life of calves. The expression of miR-10, miR-146, miR-191, miR-33, miR-7, miR-96, miR-99/100, miR-486, miR-145, and miR-211 displayed significant temporal differences (FDR < 0.05), while miR-192/215, miR-194, miR-196,miR-205 and miR-31 revealed significant regional differences (FDR<0.05) throughout the GIT. Expression levels of miR-15/16, miR-29 and miR-196 were positively correlated with copy numbers of 16S rRNA gene of Bifidobacterium or Lactobacillus species or both of them (P < 0.05). Functional analysis using Ingenuity Pathway Analysis identified above mentioned differentially expressed miRNAs as potential regulators of gut tissue cells proliferation and differentiation, and bacterial density-associated miRNAs as modulators of development of lymphoid tissues (miR-196), maturation of dendritic cells (miR-29) and development of immune cells (miR-15/16). Conclusion: This present study revealed temporal and regional changes in miRNA expression, correlation between miRNA expression and microbial population during early life suggest their potential roles in host-microbial interactions during the gut development. Overall design: Small intestine (mid-jejunum and ileum) and rumen samples were collected from on newborn (30 min after birth; n = 3), 7-day-old (n = 6), 21-day-old (n = 6), and 42-day-old (n = 6) dairy calves. The miRNA profiling was performed using high-throughput miRNA sequencing (illumina HiScanSQ platform).