[en] MicroRNAs (miRNAs) are a class of small noncoding RNAs of about 22 base pairs that play multiple roles in regulating most biological processes. MiRNAs can be very useful in livestock as animal health biomarkers or as markers of phenotypes of interest during the process of genomic selection in breeding programs. Although studies have been carried out on the expression of miRNAs in different tissues of the sheep, there has not been a study that integrates many tissues of the sheep and this type of work is very important to identify tissue-specific miRNAs and to have a global approach of the expression of miRNA across tissues. Therefore, in this work we have collected 152 miRNA-seq raw samples of 15 different works from databases and classified them into 19 tissues. We have predicted novel miRNAs and quantified them together with known miRNAs using miRDeep2. All processes and analyses have been done using the same computer programs, methodology and genome, to analyze data in a comparable and uniform way. To identify the tissue-specific miRNAs we have used a tissue specificity index (TSI) called tau. We have seen that the expression in the tissues we have studied is dominated by a few miRNAs, with a single miRNA dominating in some tissues. We have also seen that the more expressed miRNAs have a role in cell cycle regulation and generally present a lower TSI. MiR-143 has been the most expressed miRNA in various tissues, which has a role in cell cycle regulation and has presented the lowest TSI. Furthermore, some of the tissue-specific miRNAs identified in this work have also been identified as tissue-specific miRNA in other species. On the other hand, we have seen that the methods or sheep breeds used in different works can cause differences in miRNAs expression in a given tissue and the importance of accessibility to updated and reliable databases has been seen. Lastly, this work has shown for the first time the expression profile of the identified miRNAs across different tissues in sheep.

[eu] MicroRNAk (miRNAk) 22 base-pare inguruko RNA ez-kodetzaile txikiak dira eta prozesu biologiko gehienen erregulazioan parte hartzen dute. Etxe-abereekin lan egitean miRNAk oso erabilgarriak izan daitezke osasun egoeraren bioindikatzaile bezala edo hazkuntza programetan intereseko fenotipoen hautaketarako markatzaile bezala. Ardian ehun desberdinetako miRNAen adierazpena ikertu den arren ez da ehun asko biltzen dituen lan integraturik egin eta lan mota horiek garrantzitsuak dira miRNA ehun espezifikoak identifikatzeko eta ehunetako miRNAen adierazpenaren ikuspegi globalago bat izateko. Hori dela eta, lan honetan datu-baseetan aurkitutako ardiaren 15 lan desberdinetako 152 miRNA-seq lagin gordin bildu eta 19 ehunetan sailkatu ditugu. MiRNA berriak aurresan eta ezagunekin batera kuantifikatu ditugu miRDeep2 programaren bidez. Prozesu eta analisi guztiak programa informatiko, metodologia eta genoma berdinarekin burutu dira, datuak era konparagarri eta uniformean aztertu ahal izateko. MiRNA ehun espezifikoak identifikatzeko tau izeneko ehun espezifitate indizea (EEI) erabili dugu. Aztertutako ehunen miRNAen adierazpenaren portzentajerik handiena miRNA gutxi batzuek hartzen dutela eta, batzuetan, miRNA bakar batek har dezakeela ikusi dugu. Baita ere ehunetako miRNA adierazienek ziklo zelularraren erregulazioan parte hartzen dutela ikusi dugu eta, orokorrean, ehun espezifikotasun baxua izan dutela. Ehun askotan miRNA adieraziena mir-143 izan da, ziklo zelularraren erregulazioan parte hartzen duena eta miRNA adierazienen artean EEI baxuena izan duena. Horrez gain, identifikaturiko miRNA ehun espezifiko batzuk beste espezie batzuetan ere miRNA ehun espezifiko bezala identifikatu direla ikusi da. Bestalde, lan desberdinetan erabilitako metodoak edo ardi arrazak ehun jakin bateko miRNAen adierazpenean desberdintasun nabariak eragin ditzakeela ikusi dugu eta datu-base eguneratu eta fidagarrien eskuragarritasunak duen garrantzia agerian geratu da. Azkenik, lan honek identifikaturiko miRNAek ehun desberdinetan zehar duten adierazpen profila erakutsi du lehen aldiz ardian.