Comparative single‐cell transcriptomic analysis reveals differences in signaling pathways in gonadal primordial germ cells between chicken ( Gallus gallus ) and zebra finch ( Taeniopygia guttata )

Abstract

Primordial germ cells (PGCs) have been used in avian genetic resource conservation and transgenic animal production. Despite their potential applications to numerous avian taxa facing extinction due to habitat loss and degradation, research has largely focused on poultry, such as chickens, in part owing to the difficulty in obtaining intact PGCs from other species. Recently, phenotypic differences between PGCs of chicken and zebra finch, a wild bird with vocal learning, in early embryonic development have been reported. In this study, we used advanced single‐cell RNA sequencing (scRNA‐seq) technology to evaluate zebra finch and chicken PGCs and surrounding cells, and to identify species‐specific characteristics. We constructed single‐cell transcriptome landscapes of chicken gonadal PGCs for a comparison with previously reported scRNA‐seq data for zebra finch. We identified interspecific differences in several signaling pathways in gonadal PGCs and somatic cells. In particular, NODAL and insulin signaling pathway activity levels were higher in zebra finch than in chickens, whereas activity levels of the downstream FGF signaling pathway, involved in the proliferation of chicken PGCs, were higher in chickens. This study is the first cross‐species single‐cell transcriptomic analysis targeting birds, revealing differences in germ cell development between phylogenetically distant Galliformes and Passeriformes. Our results provide a basis for understanding the reproductive physiology of avian germ cells and for utilizing PGCs in the restoration of endangered birds and the production of transgenic birds.

Pronounced early differentiation underlies zebra finch gonadal germ cell development

“…Our studies validated some findings of Jung et al, 2021, on heterogeneity of zebra finch PGCs, as well as differences between chicken and zebra finch (Jung et al, 2023). These include the expression of SMC1B in zebra finch but not chicken germ cells, and of stem cell marker expression differences between zGC clusters.…”

“…Jung et al (2023) highlight a potentially enhanced role for Activin signaling in zebra finch PGCs compared to chicken. Consistent with this hypothesis, our analyses show elevated expression of Activin receptors ACVR1 and ACVR2B in the zGC2 cluster compared to zGC1.…”

“…In our study, we sought to identify potential molecular differences that could explain the efficacy in in vitro culture conditions between chicken and zebra finch gonadal PGCs, using scRNAseq data, and compared our findings to two recent reports conducted independently (Jung et al, 2021, 2023). We found that by HH28 of both sexes, there exist two populations of zebra finch germ cells (not three as found in Jung et al, 2021), but only one at the same stage in chicken.…”

Strategies for the Generation of Gene Modified Avian Models: Advancement in Avian Germline Transmission, Genome Editing, and Applications

“…Transgenic zebra finches carrying the GFP gene under the control of the human ubiquitin-C promoter were generated and GFP-expressing cells located in the forebrain could be traced and analyzed [ 38 , 200 ]. Gonadal PGCs of zebra finch are heterogenous, and the signaling pathways contributing to their development differ from those of chickens [ 201 , 202 ]. In addition, a retrovirus-mediated immortalized zebra finch fibroblast cell line was established and the Sox9 gene was knocked out using CRISPR/Cas9 [ 203 ].…”

The Omics Revolution in Understanding Chicken Reproduction: A Comprehensive Review

“…This technique enables the study of gene expression patterns at the individual cell level, resulting in a more complete understanding of the heterogeneity within complex tissues such as the chicken reproductive system. By analyzing the transcriptomes of individual germ cells, follicle cells, and embryonic cells, we can discover the regulatory networks and cell-to-cell communication routes involved in chicken reproduction [ 93 ]. Overall, transcriptomics has transformed our understanding of the molecular pathways that drive chicken reproduction and can be used to understand the complexity of gene expression in chickens by using modern techniques such as RNA sequencing, microarray analysis, qRT-PCR, and single-cell RNA sequencing [ 94 ].…”