Mammals express three lipin proteins, namely lipin1, lipin2 and lipin3, and are encoded by their respective genes Lpinl, Lpin2, and Lpin3 (Peterfy et al., 2001).
A variant near Lpin3 has been associated with fasting serum glucose levels in healthy individuals (Scott et al., 2012).
In this study, we examined the ontogenetic expression of Lpin2 and Lpin3 in two breeds of fat-tailed sheep with phenotypic differences in tail fat phenotype, and analyzed the associations between gene expression and slaughter and tail traits, with the aims to reveal the ontogenetic expression patterns of the two genes and explore the potential functions of lipin2 and lipin3 in fat metabolism as well as other possible metabolic pathways in sheep.
Four males and four females from every growth stage (2, 4, 6, 8, 10, and 12 months of age) totaling 48 animals for each breed were used to examine the ontogenetic expression of Lpin2 and Lpin3. Tissues such as liver, kidney, small intestine, femoral biceps, reproductive organs (testis and ovary), perirenal and tail fats were rapidly collected after slaughtering, weighed and placed in liquid nitrogen and stored at -80[degrees]C until subsequent laboratory analysis.
Lpin2 and Lpin3 mRNA expression was normalized to housekeeping genes RPL13A and B2M mRNA levels respectively, data analysis was performed using the comparative CT method (Livak and Schmittgen, 2001), and the final relative expression was obtained by geometric mean.
The relative abundance of Lpin2 and Lpin3 mRNA was analyzed by using general linear model in SPSS Statistics 19.0 software package (SPSS Science, Chicago, IL, USA).
The relative abundance of Lpin2 and Lpin3 mRNA both displayed great differences in breeds (p<0.001, p<0.01), months of age (p<0.001) and tissues (p<0.001).
Breeds and sexes: The average abundance of Lpin2 and Lpin3 mRNA for all tissues in GLT (1.042 [+ or -] 0.042, 1.155 [+ or -] 0.041) both were significantly higher than those in STH (0.671 [+ or -] 0.043, 0.977 [+ or -] 0.042) (p<0.001, p<0.01) (Table 3).
Tissues: Both Lpin2 and Lpin3 were expressed in all detected tissues, the highest level of Lpin2 expression was found in perirenal fat (1.587 [+ or -] 0.079), with significant differences from those found in tail fat (p<0.05), liver, kidney and reproductive organs (testis and ovary) (p<0.01), as well as small intestine and femoral biceps (p<0.001).
Months of age: Lpin2 and Lpin3 mRNA abundance varied greatly along with the growth stages in both breeds of sheep, the greatest level of Lpin2 occurred at 10 months of age, which was much higher than those at 4, 12, and 2 months of age (p<0.05), with the lowest expression at 6 and 8 months of age (p<0.01).
Two-way interactions also significantly impacted Lpin3 mRNA expression.