Systematic Identification of Long Noncoding RNAs in Immature and Mature Porcine Testes

Thousands of long noncoding RNAs (lncRNAs) have been identified in mouse, rat, and human testes, some of which play important roles in testis development and spermatogenesis. However, systematic analysis of lncRNAs expressed in postnatal pig testes has not been reported. Thus, in this study, we present the expression and characterization of lncRNAs in immature (30-day-old [D30]) and mature (180-day-old [D180]) pig testes. A total of 90 440 168 (85.75%) and 97 001 700 (95.35%) 150-base-pair paired-end clean reads were generated in D30 and D180 cDNA libraries, respectively, using the Illumina HiSeq 4000 platform; 36 727 transcripts were assembled in those two libraries, 777 lncRNA transcripts from 752 lncRNA gene loci were identified using the highly stringent pipeline, and 101 of those lncRNA transcripts were significantly differentially expressed. Those lncRNAs shared some characteristics with other mammals, including fewer exons, shorter length and exon length, and lower expression level compared with those of protein-coding genes; 402 protein-coding genes (<10 kb) were found as nearest neighbors of 294 out of 752 lncRNA genes, and gene ontology enrichment showed that they were enriched in transcription- and development-related processes. Fifteen differentially expressed and 10 novel lncRNAs were randomly selected and validated by quantitative polymerase chain reaction (PCR) and reverse transcriptase PCR. In addition, one of the 10 novel lncRNAs was further confirmed using RACE clone technology. This study provides a catalog of porcine testes lncRNAs for further understanding their regulation roles in pig testis development and spermatogenesis.