Gene Location, Expression, and Function of FNDC5 in Meishan Pigs

Xiaorong An,Wentao Cui,Chunbo Cai,Gaojun Xiao,Lili Qian,Biao Li,Shanshan Xie,Ting Gao,Kui Li,Shengwang Jiang

doi:10.1038/s41598-017-08406-y

Abstract

Irisin is a new muscular regulatory factor that is generated by the cleavage of its precursor protein fibronectin type III domain-containing protein 5 (FNDC5). Irisin promotes fat consumption due to its stimulatory role in the browning of the adipocytes in mice. Currently, there is no report on FNDC5 functions in pigs as model animals. In this study, we investigated the expression patterns and functions of FNDC5 in Meishan pigs. Our results showed that FNDC5 gene in Meishan pigs contains five transcripts, all of which can be translated into functional intact irisin proteins. Porcine FNDC5 is mainly expressed in skeletal muscle, with the expression level being significantly higher during the embryonic and juvenile periods than in the adulthood stage. In vitro study showed that FNDC5 stimulates the proliferation and adipogenic differentiation of primary adipocytes isolated from Meishan pigs, and FNDC5 enhances the expression of browning marker genes during adipogenic differentiation. Our study was the first report on FNDC5 expression patterns and functions in pigs. Data from this study provide valuable information related to the study on FNDC5 functions and future development of novel treatment for obesity.

Highlights

Obesity is a worldwide metabolic disorder that results in serious diseases such as type 2 diabetes[1]
It was found that fibronectin type III domain-containing protein 5 (FNDC5) can be cleaved to form a novel protein, irisin, which increases the expression of the uncoupling protein 1 (UCP1) in adipose tissue and enhances the browning of white fats in mice[14]
By looking at DNA sequence of human FNDC5 (Gene ID: 252995) on NCBI web site, we found that the corresponding gene sequence of human FNDC5 encoding the missing 43-amino acids identified in Meishan pigs is contained in two exons: missing parts 1 and 2 (Fig. 1B)

Summary

Results

Identification of DNA sequence encoding the intact irisin protein in porcine genome. Amino acid sequences of irisin are highly conserved among species, with the homology of human and mouse being 100% (Fig. 1A). The number of adipocytes in the culture medium supplemented with recombinant FNDC5 protein (200 ng/ml) started to increase significantly on day 1, and kept increasing more significantly on days 2, 3 and 4 (Fig. 4E) These in vitro results clearly indicate that FNDC5 can stimulate the proliferation of primary adipocytes isolated from Meishan pigs. FNDC5 increased the expression of PPARγ (Fig. 5C).These in vitro results clearly indicate that FNDC5 can stimulate adipogenic differentiation of primary adipocytes in Meishan pigs. Our results indicate that FNDC5 can enhance the expression of browning marker genes of primary adipocytes in Meishan pigs. We obtained five transcripts from porcine FNDC5 gene by performing RACE experiments All these 5 transcripts contain the base sequence encoding an intact irisin protein, which is not consistent with the results predicted by the NCBI database. Our data on the expression patterns and functions of FNDC5 in Meishan pigs provide valuable information for further research and development of FNDC5 as a novel treatment of obesity

Materials and Methods

Author Contributions

Additional Information