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It has been established that through binding to bone morphogenetic proteins (BMPs), bone morphogenetic protein receptor I B (BMPR1B) can mediate transforming growth factor β (TGF-β) signal transduction, and is involved in the regulation of several biological processes, such as bone and muscle formation and homeostasis, as well as folliculogenesis. Also known as FecB, BMPR1B has been reported as the major gene for sheep prolificacy. A number of previous studies have analyzed the relationship between single nucleotide polymorphisms (SNPs) in this gene and its related performance. In recent years, with the illustration of the effect of retrotransposon insertion on the expression of the proximal genes or phenotypic variation, retrotransposon insertion polymorphisms (RIPs) have been used as a novel type of molecular marker in the evaluation of evolution, population structure and breeding of plant and domestic animals. In this study, the RIPs in porcine BMPR1B gene were excavated, and thereafter verified using a comparative genome and polymerase chain reaction (PCR). The potential effects of phenotype, gene expression and functions related to RIPs were also explored. The results showed that 13 distinct RIPs were identified in introns of porcine BMPR1B. Among these, only BMPR1B-SINE-RIP9 and BMPR1B-LINE-RIP13 displayed a close relationship with the growth traits of Large White pigs. Moreover, the total number of BMPR1B-SINE+/+-RIP9 individuals born was found to be significantly higher than that of SINE−/− (p < 0.05). These two RIPs showed an obvious distribution pattern among Chinese indigenous breeds and Western commercial breeds. The expression of BMPR1B in ovaries of adult BMPR1B-SINE+/+-RIP9 Sushan pigs was found to be significantly higher in comparison to those of BMPR1B-SINE−/−-RIP9 (p < 0.05). SINE insertion of BMPR1B-SINE-RIP9 and LINE insertion of BMPR1B-LINE-RIP13 were observed to significantly increase the activity of Octamer binding transcription factor 4 (OCT4) minipromoter in CHO and C2C12 cells (p < 0.01). Therefore, these two RIPs could serve as useful molecular markers for modulating the growth or reproductive traits in assisted selection of pig breeding, while the mechanisms of the insertion function should be studied further. [ABSTRACT FROM AUTHOR]

Retrotransposon is an important component of the mammalian genome. Previous studies have shown that the expression of protein-coding genes was affected by the insertion of retrotransposon into the proximal genes, and the phenotype variations would be related to the retrotransposon insertion polymorphisms (RIPs). In this study, leptin (LEP), leptin receptor (LEPR), and leptin receptor overlapping transcript (LEPROT), which play important roles in the regulation of fat synthesis and body weight, were screened to search for the RIPs and their effect on phenotype and gene expression, as well as to further study the function of the insertion. The results showed that three RIPs located in intron 1 of LEPROT and intron 2 and 21 of LEPR were identified, and they were all SINEA1, which was one type of retrotransposon. The SINE insertion at the LEPROT was the dominant allele in native pig breeds. The age of 100 kg body weight of SINE+/+ Large White individuals was significantly higher than those of SINE+/− and SINE−/− individuals (p < 0.05). The LEPROT gene expression in the liver and suet of 30-day-old SINE−/− Sujiang piglets were significantly higher than those of SINE+/+ and SINE+/− piglets (p < 0.01). The dual-luciferase reporter gene assay showed that SINE insertion in PK15 and 3T3-L1 cells significantly reduced the promoter activity of the LEPROT gene (p < 0.01). Therefore, SINE insertion can be a repressor to reduce the expression of LEPROT and could be a useful molecular marker for assisted selection of growth traits in pig breeding. [ABSTRACT FROM AUTHOR]