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P-element-induced wimpy testis-interacting RNAs (piRNAs) are small RNAs that are essential for mammalian spermatogenesis and testicular development. Comparative analyses of the molecular mechanisms of spermatogenesis among different organisms are therefore dependent on accurate piRNA characterizations. In this study, we identified piRNAs in the testes of two breeds of Mongolian sheep: the Sunite (SN), which has a low reproductive rate, and Small-tailed Han (STH), which has a high reproductive rate. A thorough understanding of the mechanisms underlying the differences in fecundity between the two breeds might provide insights for the improvement of fertility and reproductive success in these and other sheep breeds. We identified 835 piRNAs and 206 piRNA clusters across the two breeds. Of these, 29 putative piRNAs were expressed in the SN samples only, and 229 putative piRNAs were expressed in the STH samples only. In addition, 206 piRNA clusters were upregulated in STH sheep as compared to the SN sheep. Functional pathway analysis indicated that the genes neighboring the predicted piRNAs were likely associated with spermatogenesis. piRNAs might thus be linked to male fecundity in sheep. Our results increase knowledge of the association between piRNAs and male fertility.

Advancements in sequencing have enabled the assembly of numerous sheep genomes, significantly advancing our understanding of the link between genetic variation and phenotypic traits. However, the genome of East Friesian sheep (Ostfriesisches Milchschaf), a key high-yield milk breed, remains to be fully assembled. Here, we constructed a near-complete and gap-free East Friesian genome assembly using PacBio HiFi, ultra-long ONT and Hi-C sequencing. The resulting genome assembly spans approximately 2.96 Gb, with a contig N50 length of 104.1 Mb and only 164 unplaced sequences. Remarkably, our assembly has captured 41 telomeres and 24 centromeres. The assembled sequence is of high quality on completeness (BUSCO score: 97.1%) and correctness (QV: 69.1). In addition, a total of 24,580 protein-coding genes were predicted, of which 97.2% (23,891) carried at least one conserved functional domain. Collectively, this assembly provides not only a near T2T gap-free genome, but also provides a valuable genetic resource for comparative genome studies of sheep and will serve as an important tool for the sheep research community. [ABSTRACT FROM AUTHOR]

A correction is presented to the article "A Near Complete Genome Assembly of the East Friesian Sheep Genome," which appeared in the July 11, 2024 online issue.

Context: Wool is one of the most important animal fibres for the textile industry, and its diameter directly affects its economic value. However, the molecular mechanisms underlying wool fibre diameter (FD) in sheep have not been fully elucidated. Aims: The aims of the work were to make an initial comparison of skin transcriptomes from sheep with wool of high and low FD, and to identify key genes affecting FD. Methods: High-throughput RNA-Seq technology was employed to explore the skin transcriptome, using three sheep with fine wool (FD <21.0 μm) and three sheep with coarse wool (FD >27.0 μm). Key results: We obtained 28 607 228 bp of clean sequence data, 78.9% (±3.8%) of which uniquely aligned to the reference genome across the six samples. In total, 19 914 mRNA transcripts were expressed (FPKM >0) in the six skin samples, among which were certain well-known genes involved in the skin–hair cycle, such as KRTAP7 - 1 , KRT14 , Wnt10b , Wnt2b , β- catenin and FGF5. Furthermore, 467 genes were significantly differentially expressed between the fine-wool and coarse-wool groups, including 21 genes with upregulated and 446 genes with downregulated expression in the sheep with lower FD. These differentially expressed genes were particularly enriched in the gene ontology processes related to lipid metabolism, skin development, differentiation and immune function (P < 0.05). The biological processes were involved in collagen catabolism, negative regulation of macromolecule metabolism, steroid hormone stimulation and lipid metabolism. A significant Kyoto Encyclopedia of Genes and Genomes pathway involving the metabolism of lipids and lipoproteins was also enriched, revealing that lipid metabolism might be one of the key factors affecting FD. The expression of these differentially expressed genes that were involved in the metabolism of lipids and lipoproteins pathway was verified by quantitative real-time PCR (qPCR). The correlation between the mRNA expression level from qPCR and RNA-Seq data was 0.999 (P < 0.001). Conclusions: The 467 differentially expressed genes, especially those involved in lipid metabolism and immune function, may play key roles in wool follicle metabolism and the expression of wool FD. Implications: This study provided valuable data for future studies aimed at elucidating the mechanisms that underlie wool follicle metabolism and wool FD. The work may also have implications for studies of the human hair follicle. Wool fibre diameter is one of the most important economic traits of sheep wool. In the present study, we discovered 467 differentially expressed genes between fine- and coarse-wool sheep, a large proportion of which are related to lipid metabolism and the immune system. Further study of these genes will help to elucidate mechanisms underlying wool follicle metabolism and wool fibre diameter. [ABSTRACT FROM AUTHOR]