MicroRNA-mediated posttranscriptional regulation is required for maintaining undifferentiated properties of blastoderm and primordial germ cells in chickens

Abstract

MicroRNAs (miRNAs) play a critical role in determining the differentiation fate of pluripotent stem cells and germ cells in mammals. However, the mechanism(s) of miRNA-mediated posttranscriptional regulation with regard to lineage specification and differentiation in chick development require further investigation. Therefore, we conducted miRNA expression profiling to explore specific miRNA signatures in undifferentiated blastoderm and primordial germ cells (PGCs). We identified seven miRNAs that are highly expressed in blastoderm and 10 that are highly expressed in PGCs. In this study, miR-302a and miR-456 for blastoderm and miR-181a* for PGCs were analyzed further for their target transcripts and regulatory pathways. Both miR-302a and miR-456 bound directly to the sex-determining region Y box 11 transcript and could act as posttranscriptional coregulators to maintain the undifferentiated state of the chicken blastoderm through the suppression of somatic gene expression and differentiation. Moreover, miR-181a* showed a bifunctional role in PGCs by binding to two different transcripts. miR-181a* inhibited the somatic differentiation of PGCs by silencing homeobox A1 expression. Additionally, miR-181a* prevented PGCs from entering meiosis through the repression of the nuclear receptor subfamily 6, group A, member 1 transcript. Collectively, our data demonstrate that in chickens miRNAs intrinsically regulate the differentiation fate of blastoderms and PGCs and that the specific timing of germ cell meiosis is controlled through miRNA expression.A t stage X, the chicken blastoderm consists of 40,000-60,000 undifferentiated embryonic cells and is able to develop pluripotent stem cells through in vitro culture (1). During chicken germline development, primordial germ cells (PGCs) first appear from the epiblast in the blastoderm and translocate to the hypoblast area of the pellucida (2, 3). During gastrulation, PGCs circulate through the vascular system and settle down in the gonadal anlagen. Such a differentiation pathway, including germ cell lineage during chicken embryo development, is a systematic process, governed by the concerted action of multiple unknown regulatory mechanisms (4-6).MicroRNAs (miRNAs) are small, noncoding RNAs ranging from 18 to 23 nucleotides that posttranscriptionally regulate gene expression in various tissues and cell types. Typically, miRNAs act as specific regulators of gene expression and are capable of controlling the fate of cells in a time-and tissue-specific manner (7, 8) through regulation of cellular differentiation, in addition to developmental patterning and morphogenesis (9-11). To date, several miRNA profiles have been classified as ESC-specific miRNAs, including miR-290-295 and miR-302-367 clusters (12, 13). However, both the miRNA expression profiling and posttranscriptional gene regulation for lineage specification, commitment, and differentiation during chicken embryo development remain largely uninvestigated. It has been shown recently that miRNA biogenesis and specific expr...

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“…In another study, the authors suggest that miR-181a*, miR-302a and miR-456 have a role in maintaining the undifferentiated state of the Primordial Germ Cell (PGC) and the Blastodermal Cell (BC) in chickens [51]. In PGC miR-181a* inhibits the meiotic transcript NR6A1 and the somatic HOXA1, modulating the different regulatory pathways for meiosis in chicken early germ cells [51].…”

“…In PGC miR-181a* inhibits the meiotic transcript NR6A1 and the somatic HOXA1, modulating the different regulatory pathways for meiosis in chicken early germ cells [51]. In PGC and BC miR-302a and miR-456 silence the expression of somatic genes (as Sex determining region Y-box, SOX11), regulating pluripotency [51].…”

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