Zoosyst. Evol. 94 (2) 2018, 401-408 | DO! 10.3897/zse.94.28099 > PENSUFT. fo Neti Gy tusrue TOR BERLIN Deciphering conserved identical sequences of mature miRNAs among six members of great apes Aftab Ali Shah!, Mushtaq Ahmad‘, Taqgweem-UI-Haq! 1 Department of Biotechnology, University of Malakand, Chakdara, Pakistan http://zoobank.org/84AC151C-9946-42BB-A41F-F30BAAB92867 Corresponding author: Aftab Ali Shah (aftabuom@gmail.com) Received | July 2018 Accepted 9 August 2018 Published 22 August 2018 Academic editor: Michael Ohl Key Words Molecular evolution Gene regulation Pre-miRNA microRNA Introduction Abstract MicroRNAs (miRNAs) are a group of small RNA molecules which act as negative reg- ulators of gene expression by controlling post-transcriptional regulation through binding to their corresponding mRNAs. Due to their small size, their nucleotide compositions are expected to be similar, but until now, the extent of similarity has not been reported in humans and their six phylogenetically closely related members of hominids. The present study allows direct comparison among six members of hominid species (Homo sapiens, Gorilla gorilla, Pan paniscus, Pongo pygmaeus, Pan troglodytes and Symphalangus syn- dactylus) in terms of their miRNA repertoire, their evolutionary distance to human, as well as, the categorization of identical species-specific miRNAs. For this purpose, a total of 2694, 370, 157, 673, 590 and 10 mature miRNA sequences of Homo sapiens, Gorilla gorilla, Pan paniscus, Pongo pygmaeus, Pan troglodytes and Symphalangus syndactylus respectively were retrieved from miRbase 22. A total of 12, 4, 4 and 3 conserved clusters with identical miRNA sequences that belong to the same gene families were found in Homo sapiens, Gorilla gorilla, Pongo pygmaeus, Pan troglodytes respectively by neigh- bor-joining method using MEGA7 software. Interestingly, cross-species comparison has also shown a set of conserved identical miRNA sequences. Homologs of human mature miRNAs with 100% sequence identity are expected to have similar functions in the stud- ied primates. Further in-vitro study is required to investigate common targets for identical miRNAs in the studied primates. miRNA clusters are transcribed as a single unit (Marco et al. 2013). The evolutionary importance of miRNA clus- MiRNAs are small (19—23nt) RNA molecules that reg- ters has been the subject of much speculation (Wang et al. ulate messenger RNA through binding to their 3’-UTR, mediated by the RNA induced silencing (RISC) complex in all living organisms (Zhang et al. 2018). Binding of miRNA to their corresponding target mRNA leads to translational repression and/ or mRNA degradation (Un- terbruner et al. 2018). To date, considerable number of mature miRNAs have been identified in Homo sapiens, Gorilla gorilla, Pan paniscus, Pongo pygmaeus and Pan troglodytes, Symphalangus syndactylus (no=2694, 370, 157, 673, 590, 10) respectively, as shown in miRbase database (http://www.mirbase.org/) (Griffiths-Jones et al. 2006; Kozomara and Griffiths-Jones 2013). It is already known that multiple miRNAs are pro- duced from the same primary transcript and majority of 2016). Many clusters contain members of the same family, suggesting an important role of gene duplication in their evolution (Berezikov 2011). On the other hand, some miRNA clusters also contain members of different miR- NA families, particularly in animal kingdom (McCreight et al. 2017). Like other gene families, miRNAs are also prone to forming paralogs, with the result that many miR- NAs appear as members of families as homologs (Hertel et al. 2006). However, the origin and evolution of these miRNA clusters has not been investigated in detail (Al- tuvia et al. 2005; Tanzer and Stadler 2004). Phylogenetic studies have shown that miRNAs are present throughout the evolution of metazoans. Comparison of pre-miIRNA sequences demonstrate that they are less conserved and Copyright Aftab Ali Shah et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which per- mits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 402 Shah, A.A. et al..: Deciphering conserved identical sequences of mature miRNAs hsa-miR-523-5p MIMAT0005449 hsa-miR-519b-5p MIMAT0005454 hsa-miR-519a-5p MIMAT0005452 hsa-miR-518e-5p MIMATO005450 _ | “luster-1 hsa-miR-522-5p MIMAT0005451 hsa-miR-519c-5p MIMAT0002831 hsa-miR-519a-2-5p MIMAT0037327 | cu cter-0 hsa-miR-520b-5p MIMAT0037325 hsa-miR-518a-5p MIMAT0005457 | 6), tar-3 hsa-miR-527 MIMAT0002862 hsa-miR-517a-3p MIMAT0002852 hsa-miR-517b-3p MIMAT0002857 hsa-miR-516a-3p MIMAT0006778 | Cluster-4 Cluster-5 hsa-miR-516b-3p MIMAT0002860 hsa-miR-3689e MIMAT0019009 hsa-miR-3689a-Sp MIMAT0018117_ Cluster-6 hsa-miR-3689b-3p MIMAT0018181 J otuster-7 hsa-miR-3689c MIMAT0019007 hsa-miR-548c-5p MIMAT0004806 hsa-miR-548am-5p MIMAT0022740 Cluster-8 hsa-miR-5480-5p MIMAT0022738 hsa-miR-570-5p MIMAT0022707 hsa-miR-548ai MIMATOO1g989_]Cluster-9 hsa-miR-548h-3p MIMAT0022723 Cluster-10 hsa-miR-548z MIMAT0018446 hsa-miR-199a-3p MIMAT0000232 Cluster-11 hsa-miR-199b-3p MIMAT0004563 hsa-miR-365b-3p MIMAT0022834 Cluster-12 b— 0.05 hsa-miR-365a-3p MIMAT0000710 Figure 1. Shows evolutionary relationships of taxa for all mature miRNAs in Homo sapiens. The analysis involved 29 nucleotide sequences. therefore are more prone to phylogenetically preserved than the mature sequences alone. High degree of identi- ty across different species was observed for mature miR- NAs (Li et al. 2010). It is also noted that many matured miRNAs are prevailing in several species and are highly conserved and are confined to specific lineages. There are several polycistronic transcripts that suggest a potential mode of evolution for polycistronic miRNAs (Truscott et al. 2016). It is already known that the miRNA repertoire has continuously increased during evolution of metazoan. However, the advent ratio of these molecules is diverse over evolutionary time (Bartel 2018). The expansions of miRNA have been linked with evolutionary innovations that lead to the diversification of bilaterians. Till now, identification of orthologous miRNAs in different species has been investigated in primates. Among the six members of great apes, Homo sapiens are the deepest explored group with 2694 mature miR- NAs miRNAs described. In the present study, we took advantage of a recently available set of mature miRNA from six members of the great ape population to system- atically detect identical miRNA by comparing patterns of intra- and inter-species sequence similarity and their evolutionary distance. Interestingly, it was found that intra- and inter-species sequence set of identical mature miRNA exists in great apes including humans. Further in-vitro study is required to investigate common targets for identical miRNAs in the studied primates. zse.pensoft.net Materials and methods Alignment of sequences and phylogenetic analysis For miRNA, a very limited open and free data is available. The miRBase is one of the highly referred databases, easily accessible and in its latest release 10883 pre-miRNAs are available. Dataset of mature miRNAs sequences of Homo sapiens (no=2694), Gorilla gorilla (no=370), Pan panis- cus (no=157), Pongo pygmaeus (no=673 mature), Pan troglodytes (no=590 mature) and Symphalangus syndacty- Jus (no=10 mature) were retrieved from miRBase sequence database (a data repository of published miRNA sequences and its annotation) (release 22.0) at http://microrna.sanger. ac.uk. ClustalW was used to generate multiple align- ments of nucleic acid sequences (Chenna et al. 2003) and MEGA7 was used to generate phylogenetic analyses using Neighbor-Joining method (Kumar et al. 2016). Results Identification of Homologous mature miRNA se- quences in intra-species in hominides Homologous sequences in Homo sapiens were clustered based on their phylogenetic relationship and sequence identity using ClustalW. Multiple alignment of mature miRNAs revealed a conserved consensus. Neighbor-Join- Zoosyst. Evol. 94 (2) 2018, 401-408 403 Table 1. List of miRNAs grouped into clusters, their genomic coordinates, gene family names and their matured miRNA sequences in Homo sapiens. S. No Members Gene Family Name Mature miRNA sequence hsa-miR-523-5p chr19: 53698385-53698471 [+] hsa-miR-519b-5p chr19: 53695213-53695293 [+] hsa-miR-519a-5p chr19: 53752397-53752481 [+] Custer dS * taser SIsesp SST S37oSSB ESTP OOOS ewe ee hsa-miR-522-5p Chehg Sa750 AN 53751297 | +] hsa-miR-519c-5p chr19: 53686469-53686555 [+] hsa-miR-519a-2-5p | le chr19: 53762344-53762430 [+] Ste er | ga IRSISEDSR ee ace ot lier Oess 7 SAO1SSST5atOD (4d ade et er noe Glisters hsa-miR-518a-5p chr19: 53731006-53731090 [+] hsa-miR-527 chr19: 53754018-53754102 [+] hsa-miR-517a-3p chr19: 53712268-53712354 [+] Cluster As “Tea Sarre LIDSp Siri: S37 D107 SS721AA [| oe ORY hsa-miR-516a-3p chr19: 53756741-53756830 [+] Clusters5— == | UGCUUCCUUUCAGAGGGU ae hsa-miR-516b-3p chr19: 53736845-53736934 [+] GiustenGh, + ee chr: 1348509 70-13489004" TE | @uGAUAUCAUGGUUCCUGGGA hsa-miR-3689a-5p MIPFO001144: mir-3689 chr9: 134849487-134849564 [-] hsa-miR-3689b-3p chr9: 134850125-134850272 [-] A AUA he ot hsa-miR-3689c SS nisAstonn IaAS4OSCOIE) Oe hsa-miR-548c-5p chr12: 64622509-64622605 [+] -————————————_ AAAAGUAA Cluster 8 hsa-miR-548am-5p chrx: 16627012-16627085 [-] ae ae acta eh hsa-miR-570-5p chr3: 195699401-195699497 [+] MIPF 17; mir-54 AAA AA A Cluster 9 hsa-miR-548ai COGS) TAMIGS TEs I chret SIPAGOS:9G1DAGO6 [1 pA Canarsie hsa-miR-548h-3p chr8: 27048853-27048963 [-] luster 1 AAAAA AAUUA A SIUSIEE TD I reaniReaans chr2: 64622509-64622605 [| strip mle cick hsa-miR-199a-3p are chr19: 10817426-10817496 [-] Cluster 11 ThsamiR-199b-3p | MIPFOQOO040; mir-199 chr9: 128244721-128244830 [.] ACAGUAGUCUGCACAUUGGUUA hsa-miR-365b-3p oe. chr: 3157/54 19-315 75520.(4] Cluster 12 shsamiR-Se5a3p. | MIPFOOQOO0061; mir-365 chr: 14309285 14309371 [+] UAAUGCCCCUAAAAAUCCUUAU ing method was used for inferring the evolutionary his- tory. The optimal tree with the sum of branch length = 2.32453654 is shown in Figure 1. The p-distance method was used for computing the evolutionary distances. The analysis involved 29 nucleotide sequences. All uncertain positions were deleted for each sequence pair. In the fi- nal dataset, there was a total of 36 positions. Evolutionary analyses were conducted in MEGA7. The conserved miR- NA sequences were grouped into 12 clusters. Number of miRNA members in each cluster, showing 100% identity in their sequences and their corresponding genomic coordi- nates, are shown in Table 1. It is interesting to note that the genomic location of all the identical miRNAs are in clus- tered form. This indicates that the genes for these identical miRNAs are originated through gene duplication during evolution and speciation. Identical miRNA sequences were also noted in Gorilla gorilla using the same phylo- genetic model. The optimal tree with the sum of branch length = 0.40606061 is shown in Figure 2. The analysis involved 12 nucleotide sequences. There were a total of 35 positions in the final dataset. However, only 12 miRNAs were found to be 100% identical. These 12 miRNAs are grouped into four clusters. Number of miRNA members in each cluster showing 100% identity in their sequences and their corresponding genomic coordinates are shown in Ta- ble 2. Interestingly, all the identified conserved miRNAs belong to a single gene family (MIPFO000020; mir-515). Similarly, identical miRNA sequences were also noted in Pongo pygmaeus using the same phylogenetic model as shown in Figure 3. The total number of identical miRNAs were 8 that were grouped into 4 clusters as shown in Ta- ble 3. The optimal tree with the sum of branch length = 1.37798461 is shown in Figure 3. The analysis involved 8 nucleotide sequences. There were a total of 32 positions in the final dataset. Likewise, identical miRNA sequences were also noted in Pan troglodytes using the same phylo- genetic model. Seven conserved miRNAs were also found in Pan troglodytes that were grouped into three clusters as shown in Table 4. The optimal tree with the sum of branch length = 0.71717172 is shown in Figure 4. The analysis involved 7 nucleotide sequences. There were a total of 26 positions in the final dataset. Identification of Homologous mature miRNA Se- quences in inter-species in Hominides To assess whether any cross-species conserved miRNA in hominids exists, all known matured miRNAs were aligned to generate multiple alignments of nucleic acid sequences using ClustalW, and MEGA7 was used to gen- erate phylogenetic analyses. The optimal tree with the sum of branch length = 3.16412289 is shown in Figure 4. There were a total of 31 positions in the final dataset. zse.pensoft.net 404 Shah, A.A. et al..: Deciphering conserved identical sequences of mature miRNAs 0.02 ggo-miR-522-5p MIMAT0036437 ggo-miR-519c-5p MIMAT0036410 ggo-miR-519a-5p MIMAT0036439 ggo-miR-518e-5p MIMAT0036427 ggo-miR-523-5p MIMAT0036414 Cluster-1 ggo-miR-518d-5p MIMAT0036429 ggo-miR-526a MIMAT0036426 ggo-miR-520c MIMAT0036420 ggo-miR-516a-5p MIMAT0036441 ggo-miR-516a MIMAT0036443 ggo-miR-520f MIMAT0036409 ggo-miR-519b MIMAT0036418 Cluster-2 | Cluster-3 | Cluster-4 Figure 2. Represents evolutionary relationships of taxa for Gorilla gorilla. The optimal tree with the sum of branch length = 0.40606061 is shown. The analysis involved 12 nucleotide sequences. L _ . 0.1 ppy-miR-520i MIMAT0036452 Cluster-1 ' ppy-miR-520d-5p MIMAT0015971 ppy-miR-518a-5p MIMAT0015951 Cluster-2 ppy-miR-527 MIMAT0015986 ppy-miR-219 MIMAT0002577 Cluster-3 ppy-miR-219-5p MIMAT0015804 ppy-miR-517c MIMAT0036449 Cluster-4 ppy-miR-517c-3p MIMAT0036448 Figure 3. Illustrate evolutionary relationships of taxa for Pongo pygmaeus. The analysis involved 8 nucleotide sequences. Using online tool jvenn (Bardou et al. 2014), it was inter- esting to note that one miRNA (CUCUAGAGGGAAGC- GCUUUCUG) was conserved and overlapping in Homo sapiens and Gorilla gorilla. Similarly, another conserved sequence (CUGCAAAGGGAAGCCCUUUC) was over- lapping in all the three members of hominde species (Homo sapiens, Pan troglodytes and Pongo pygmaeus) as shown in Figures 5, 6. It was also noted that one miRNA (ACAGUAGUCUGCACAUUGGUUA) was overlap- ping in Homo sapiens and Pan troglodytes. zse.pensoft.net Discussion MiRNA-mediated gene regulation is novel mechanism among all lineages in animal kingdom (Zhang et al. 2004). Due to their smaller size, many known miRNA genes in animal genomes are found as clusters. MiRNA clusters are a group of related miRNAs closely localized in the genome with an evolution that remains poorly understood (Chen et al. 2015). Therefore, most of the clusters are transcribed as a single polycistronic transcripts (Lagos-Quintana et Zoosyst. Evol. 94 (2) 2018, 401-408 405 ptr-miR-1283b MIMAT0036458 ptr-miR-518g-5p MIMAT0036454 =| Cluster-1 ptr-miR-527 MIMAT0008212 ptr-miR-520h MIMAT0008204 Cluster-2 ptr-miR-520g MIMAT0008203 ptr-miR-199b MIMAT0008062 Cluster-3 ptr-miR-199a-3p MIMAT0009192 0.05 Figure 4. Represents evolutionary relationships of taxa for Pan troglodytes. The optimal tree with the sum of branch length = 0.71717172 is shown. The analysis involved 7 nucleotide sequences. Table 2. List of miRNAs grouped into clusters, their genomic coordinates, gene family names and their matured miRNA sequences in Gorilla gorilla. S. No No. of members | Gene family Mature miRNA sequence ggo-miR-522-5p chr19; 53095952-53096058 [+] ggo-miR-519c-5p chr19: 53038851-53038969 [+] Cluster 1 ggo-miR-519a-5p chri9r53097153-53097260 [+] ggo-miR-518e-5p chr19: 53073319-53073416 [+] CUCUAGAGGGAAGCGCUUUCUG ggo-miR-523-5p chr19: 53042042-53042160 [+] ggo-miR-518d-5p PHEECORCOS Ce TE chr19: 53078317-53078435 [+] Cluster 2 | ggo-miR-526a ‘an chr19: 53069990-53070073 [4] ggo-miR-520c chr19: 53049906-53050015 [+] ggo-miR-516a-5p chr19: 53101171-53101280 [+] ggo-miR-516a chr19: 53105582-53105691 [+] ggo-miR-520f chr19: 53025391-53025489 [+] Cluster 4 ; AAGUGCUUCCUUUUAGAGGGUU ggo-miR-519b chr19: 53044871-53044969 [+] Cluster 3 UUCUCGAGGAAAGAAGCACUUUC Table 3. List of miRNAs grouped into clusters, their genomic coordinates, gene family names and their matured miRNA sequences in Pongo pygmaeus. S. No No. of members Gene Family Genomic coordinate Mature miRNA sequence ppy-miR-520i chr19: 55513927-55514025 [+] Cluster 1 CUACAAAGGGAAGCCCUUUC ppy-miR-520d-5p chr19: 55491990-55492076 [+] MIPFOOOO020; mir-515 ppy-miR-518a-5p chr19: 55505640-55505726 [+] Cluster 2 CUGCAAAGGGAAGCCCUUUC chr19: 55533164-55533250 [+] ppy-miR-219 NW_002874576.1: 1044940-1045049 [+] Cluster 3 MIPFOOQOO044; mir-219 UGAUUGUCCAAACGCAAUUCU ppy-miR-219-5p chr9: 125361031-125361127 [-] -miR-517c Cluster 4 aii MIPFOOOO020; mir-515 chr19: 55485875-55485961 [+] AUCGUGCAUCCCUUUAGAGUGU ppy-miR-517c-3p ppy-miR-527 zse.pensoft.net 406 + 0.05 Figure 5. A comparative evolutionary relationships of taxa for Homo sapiens, Gorilla gorilla, Pongo pygmaeus and Pan troglo- Shah, A.A. et al..: Deciphering conserved identical sequences of mature miRNAs hsa-miR-519b-5p MIMAT0005454 hsa-miR-519c-5p MIMAT0002831 hsa-miR-523-5p MIMAT0005449 hsa-miR-519a-5p MIMAT0005452 hsa-miR-518e-5p MIMAT0005450 hsa-miR-522-5p MIMAT0005451 ggo-miR-523-5p MIMAT0036414 ggo-miR-519c-5p MIMAT0036410 ggo-miR-522-5p MIMAT0036437 ggo-miR-519a-5p MIMAT0036439 ggo-miR-518e-5p MIMAT0036427 hsa-miR-519a-2-5p MIMAT0037327 hsa-miR-520b-5p MIMAT0037325 ggo-miR-518d-5p MIMAT0036429 ggo-miR-526a MIMAT0036426 ggo-miR-520c MIMAT0036420 ggo-miR-516a-5p MIMAT0036441 ggo-miR-516a MIMAT0036443 ppy-miR-520i MIMAT0036452 ppy-miR-520d-5p MIMAT0015971 ppy-miR-518a-5p MIMAT0015951 ppy-miR-527 MIMAT0015986 pir-miR-1283b MIMAT0036458 pir-miR-518g-5p MIMAT0036454 pir-miR-527 MIMAT0008212 hsa-miR-518a-5p MIMAT0005457 hsa-miR-527 MIMAT0002862 ppy-miR-517c MIMAT0036449 ppy-miR-517c-3p MIMAT0036448 hsa-miR-517b-3p MIMAT0002857 hsa-miR-517a-3p MIMAT0002852 ptr-miR-520h MIMAT0008204 ptr-miR-520g MIMAT0008203 hsa-miR-516a-3p MIMAT0006778 hsa-miR-516b-3p MIMAT0002860 ptr-miR-199b MIMAT0008062 ptr-miR-199a-3p MIMAT0009192 hsa-miR-199a-3p MIMAT0000232 hsa-miR-199b-3p MIMAT0004563 hsa-miR-548h-3p MIMAT0022723 hsa-miR-548z MIMAT0018446 ppy-miR-219 MIMAT0002577 ppy-miR-219-5p MIMAT0015804 hsa-miR-365b-3p MIMAT0022834 hsa-miR-365a-3p MIMAT0000710 hsa-miR-3689e MIMAT0019009 hsa-miR-3689a-5p MIMAT0018117 hsa-miR-3689b-3p MIMAT0018181 hsa-miR-3689c MIMAT0019007 hsa-miR-570-5p MIMAT0022707 hsa-miR-548ai MIMAT0018989 hsa-miR-5480-5p MIMAT0022738 hsa-miR-548c-5p MIMAT0004806 hsa-miR-548am-5p MIMAT0022740 dytes. The analysis involved 54 nucleotide sequences. zse.pensoft.net Zoosyst. Evol. 94 (2) 2018, 401-408 407 Table 4. List of miRNAs grouped into clusters, their genomic coordinates, gene family names and their matured miRNA sequences in Pan troglodytes. S. No No. of members Gene family Genomic coordinate Mature miRNA sequence ptr-miR-1283b chr19: 56105638-56105756 [+] Cluster 1 | ptr-miR-518g-5p chr19: 56078436-56078532 [+] CUGCAAAGGGAAGCCCUUUC ptr-miR-527 MIPFOOOO020; mir-515 | chr19: 56101441-56101526 [+] ptr-miR-520h chr19: 56089945-56090033 [+] Cluster 2 BtemiRes 20s chr19: 56069121-56069209 [4] ACAAAGUGCUUCCCUUUAGAGUGU ptr-miR-199b A: chr9: 106385739-106385847 [-] Cluster 3 ptr-miR-199a-3p MIPFOOQOO4O; mir-199 chr19: 11396978-11397047 [ ] ACAGUAGUCUGCACAUUGGUUA qgo-miRNAs ppy-miRNAs Size of each list ppy-miRNAs pir-miRAAs hsa-miRNAs ggo-miRNAs Figure 6. Venn diagram representing number of overlapping miRNA in Homo sapiens, Gorilla gorilla, Pongo pygmaeus and Pan troglodytes. al. 2003; Mourelatos et al. 2002). It was found that these clusters are highly conserved in most mammals. Insertions of new miRNAs, deletions of individual miRNAs, and a cluster duplication observed in different species suggest an actively evolving cluster. In the present study, intra-species and inter-species conserved identical miRNAs were iden- tified in the six species of hominoids. Interestingly, there were few miRNAs that were conserved across all studied Species, indicating their evolutionary distance to humans, as well as, the categorization of identical species-specific miRNAs were identified in stx members of great apes. It was investigated that most conserved miRNA clusters in all the studied members of hominoids belong to the two families 1.e., mir-515 and mir-199, suggesting that the an- cestral clusters may be originated by tandem duplication. It has been demonstrated that some miRNA genes exhib- ited the phenomena of clustering (Kurkewich et al. 2018). Interestingly, several studies have shown that miRNA clusters comprise of two or more miRNA genes that dis- play high level of identity in sequences. Moreover, they are situated contiguously with each other in the genome (Gonzalez-Vallinas et al. 2018). Through experimental zse.pensoft.net 408 Shah, A.A. et al..: Deciphering conserved identical sequences of mature miRNAs and computational identification, the miRBase database is one of the primary repository resources for collecting miRNA genes (Griffiths-Jones et al. 2007; Kozomara and Griffiths-Jones 2013). No futuristic data related to miR- NA clusters is available in miRBase. Similarly, no further information about miRNA gene clusters was rendered to explore the evolutionary conservation between miRNA clusters across several species. The present data highlight- ed intra and inter phylogenetic relationship of matured miRNA in six species of great apes. Conclusion In this comparative study, conserved identical miRNA sequences were found among four hominid species. The applied prediction algorithm (mentioned in the materi- als and method section) proves several criteria based on similarity to identified conserved sequences of miRNAs to detect both more distantly-related and closely-related homologs. Further study is required to identify potential targets for identical miRNAs in the studied primates. Compliance with ethical standards Conflict of interest: No conflict of interest exists. Ethical approval: This article does not contain any study with human participants or animals performed by any of the authors. References Altuvia Y et al. 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