Meiotic initiation in chicken germ cells is regulated by Cyp26b1 and mesonephros

Strain-specific variations in the culture of chicken primordial germ cells

Efficient long-term cultivation of chicken primordial germ cells (cPGCs) is essential for various avian research and biotechnology applications. Our study aimed to address the challenge of inconsistent culture success by investigating strain-specific variations and optimizing culture conditions using two distinct media: Ovotransferrin-enriched medium (OTM) and chicken serum-supplemented medium (CSM). We demonstrated that each chicken strain has unique nutritional requirements, with Hubbard cPGCs thriving in OTM and Bovans cPGCs favoring CSM. This strain-specific variation was effective in derivation and proliferation rates and the expression of stem cell-specific markers such as POU5F3/OCT4 and NANOG. Furthermore, our study confirmed the sustained germ cell identity of long-term cultured cPGCs through the expression of DAZL, DDX4, and EMA1 germ cell markers. We also showed that cultured cPGCs retained their migratory abilities and transfectability, successfully generating G0 germline chimeras and G1 transgenic Bovans chickens. These findings highlight the importance of optimized culture conditions depending on the genotype to enhance the viability and genetic stability of cPGCs, paving the way for more effective genetic modifications and conservation strategies in avian species.

Analysis of the differentially expressed genes in the combs and testes of Qingyuan partridge roosters at different developmental stages

BACKGROUND

The sexual maturity of chickens is an important economic trait, and the breeding of precocious and delayed puberty roosters is an important selection strategy for broilers. The comb serves as an important secondary sexual characteristic of roosters and determines their sexual precocity. Moreover, comb development is closely associated with gonad development in roosters. However, the underlying molecular mechanism regulating the sexual maturity of roosters has not yet been fully explored.

RESULTS

In order to identify the genes related to precocious puberty in Qingyuan partridge roosters, and based on the synchrony of testis and combs development, combined with histological observation and RNA-seq method, the developmental status and gene expression profile of combs and testis were obtained. The results showed that during the early growth and development period (77 days of age), the development of combs and testis was significant in the high comb (H) group versus the low comb (L) group (p < 0.05); however, the morphological characteristic of the comb and testicular tissues converged during the late growth and development period (112 days of age) in the H and L groups. Based on these results, RNA-sequencing analysis was performed on the comb and testis tissues of the 77 and 112 days old Qingyuan Partridge roosters with different comb height traits. GO and KEGG analysis enrichment analysis showed that the differentially expressed genes were primarily enriched in MAPK signaling, VEGF signaling, and retinol metabolism pathways. Moreover, weighted correlation network analysis and module co-expression network analysis identified WNT6, AMH, IHH, STT3A, PEX16, KPNA7, CATHL2, ROR2, PAMR1, WISP2, IL17REL, NDRG4, CYP26B1, and CRHBP as the key genes associated with the regulation of precocity and delayed puberty in Qingyuan Partridge roosters.

CONCLUSIONS

In summary, we identified the key regulatory genes of sexual precocity in roosters, which provide a theoretical basis for understanding the developmental differences between precocious and delayed puberty in roosters.

Genetic Regulation of Avian Testis Development

As in other vertebrates, avian testes are the site of spermatogenesis and androgen production. The paired testes of birds differentiate during embryogenesis, first marked by the development of pre-Sertoli cells in the gonadal primordium and their condensation into seminiferous cords. Germ cells become enclosed in these cords and enter mitotic arrest, while steroidogenic Leydig cells subsequently differentiate around the cords. This review describes our current understanding of avian testis development at the cell biology and genetic levels. Most of this knowledge has come from studies on the chicken embryo, though other species are increasingly being examined. In chicken, testis development is governed by the Z-chromosome-linked DMRT1 gene, which directly or indirectly activates the male factors, HEMGN, SOX9 and AMH. Recent single cell RNA-seq has defined cell lineage specification during chicken testis development, while comparative studies point to deep conservation of avian testis formation. Lastly, we identify areas of future research on the genetics of avian testis development.