Integrative lncRNAs function related to metabolic were selected using high-throughput RNA-seq screening, and a workflow for the discovery and characterization of functional lncRNAs were established in yak at different ages. The data obtained in this experiment support that lncRNAs was a crucial component of metabolism. Both the expression profile of lncRNAs and RNAs have change coordinately according to different developmental ages including 1 day, 15 months, and 5 years. Moreover, groups of metabolism relative lncRNAs were regulated in liver by ages, and their expression often changes significantly in yaks at diverse ages, supporting their potential biological significance.
Identifying lncRNAs regulating metabolic and finding its functional properties is still a hard task in animals and only a few lncRNAs could regulate metabolism were reported for now [29–32]. Moreover, it is impossible to directly determine the role of lncRNAs in metabolic process, for the reason of its non-coding feature. In order to get over this difficulty, this article build a functional lncRNAs detection method by interactive analysis of lncRNAs in liver of yaks at different ages. This integrated approach efficiently reduce 288 age-adjusted lncRNAs to 88 putative metabolic lncRNAs which is differentially expressed at least in two age stages.
Only a few previous published papers showed that lncRNAs play a critical role in regulating metabolic pathway in mice [29–32], and certainly there is no report on the function of lncRNAs in yak. In order to understand the processes of yak liver metabolism in depth, more lncRNAs need to be discovered and characterized, and confirming the workflow of lncRNAs could speed up the selection and characterization of metabolic lncRNAs, which offered more perspective for the complex metabolism networks.
Making out the impact of lncRNAs in metabolic pathways at different developmental ages could enhance the unknown fields of complex metabolic physiology. Comparative genomics method had been widely used in revealing potential functions of novel protein-coding genes based on information of homologous genes or protein motifs, but has proved to be noneffective in finding the function of lncRNAs [33]. For most lncRNAs have not been functionally studied, and more importantly, lncRNAs were much more conservative than mRNAs, even between closely related model organisms [34]. Since most lncRNAs are unique to different animals, it is difficult to infer their role according to the sequence matching or evolutionary records [35].
For it is hard to predict functions for lncRNAs, it becomes very difficult to discover and characterize lncRNAs that regulate metabolism. Since metabolism is essential for almost all the biological processes, all organisms, any controlling with vital metabolic pathways is achieved usually through reconnecting metabolic fluxes. Therefore, a strict functional measurement is needed to determine critical points in metabolic regulation. To check the function of lncRNA further in animal models, it is firstly necessary to correctly infer the functional information of lncRNAs. In addition, the results of this experiment can also be beneficial to design targeted and detection methods to determine the unique metabolism in specific lncRNA, which is usually suppressed in complex interaction or compensation situation.
To further determine if this integrative transcriptome analysis is sufficient to identify lncRNAs that function as metabolic regulators, we tested the specific metabolic function for one lncRNA (TCONS_00098792) in mouse hepatic AML12 cell line. These in vitro results indicate that this novel LncRNA perform its function by regulating SLC22A7 (Fig. 5). It is reported that SLC22A7 is a facilitative transporter of cGMP, which mediates a host of cellular responses to various stimuli, resulting in the regulation of many critical physiologic functions [36]. Others also reported that SLC22A7 is a sodium-independent multi-specific organic anion/dimethyldicarboxylate exchanger [37]. Moreover, SLC22A7 expressed highly in liver tissue and play critical role in liver [38]. Taken together, our result showed a novel LncRNA potentially play its role by regulating SLC22A7 in yak liver, which also indicate this efficient method to predict metabolic lncRNAs could significantly accelerate the identification of important lncRNAs metabolic regulators.