The new technology of high‐throughput single‐cell RNA sequencing (10 × scRNA‐seq) was developed recently with many advantages. However, it was not commonly used in farm animal research. There are few reports for the gene expression of goat ovarian follicle granulosa cells (GCs) during different developmental stages. In the current investigation, the gene expression of follicle GCs at different stages from two populations of Ji'ning grey goats: high litter size (HL; ≥3/L; 2 L) and low litter size (LL; ≤2 /L; 2 L) were analysed by scRNA‐seq. Many GC marker genes were identified, and the pseudo‐time showed that GCs developed during the time course which reflected the follicular development and differentiation trajectory. Moreover, the gene expression difference between the two populations HL versus LL was very clear at different developmental stages. Many marker genes differentially expressed at different developmental stages. ASIP and ASPN were found to be highly expressed in the early stage of GCs, INHA, INHBA, MFGE8 and HSD17B1 were identified to be highly expressed in the growing stage of GCs, while IGFBP2, IGFBP5 and CYP11A1 were found to be highly expressed in late stage. These marker genes could be used as reference genes of goat follicle GC development. This investigation for the first time discovered the gene expression patterns in goat follicle GCs in high‐ or low‐fertility populations (based on litter size) by scRNA‐seq which may be useful for uncovering the oocyte development potential.

The phenotypic variation of different organisms cannot be completely explained using Mendelian genetics which is inheritable based on DNA sequence (Richards, 2006). Epigenetics plays important roles in genetic variations which means except the change in DNA sequence, chromatin remodelling, DNA methylation, X chromosome inactivation and non-coding RNA regulation can also be stably transferred during cell proliferation, growth and development (Greally, 2018).Moreover, some epigenetic characteristics (such as DNA methylation) in certain germ cells can be inherited across generations (Rodgers et al., 2015). The gene expression patterns of offspring depend on their parents which is called genomic imprinting in mammals (Ferguson-smith, 2011). Epigenetic silencing of inactive alleles (such as DNA methylation) results in the differential allele expression (Xu et al., 2001). DNA methylation, as an epigenetic modification slowly coming into sight, is a process in which methyl is selectively added to cytosine by DNA methyltransferase (DNMT) to form 5-cytosine. Some evidence suggests DNA methylation can be inherited across generations through gametes (Daxinger & Whitelaw, 2012).

(1) Background: It has been recognized that the origin of fat-tailed sheep occurred within coarse wool breeds and that this character was introgressed several times into thin-tailed populations. However, no study has investigated this idea for Egyptian breeds using mtDNA analyses. (2) Methods: Using new sequences of the control region, we constructed a database of 467 sequences representing 37 breeds including fat- and thin-tailed ones with 80 Egyptian individuals belonging to six local breeds (Barki, Fallahi, Ossimi, Rahmani, Saidi, Sohagi). The phylogenetic tree obtained with the maximum likelihood method was submitted to the Newick Extra program to count the direct and indirect links between the individuals of each breed. (3) Results: Several Egyptian breeds were strongly connected to “primitive” thin-tailed breeds from Europe, indicating a clear genetic background of the “thin tail” breed type that supports the view of archeologists. In several cases, we suspected Western Asian breeds to be involved in the introgression of the fat tail character. In contrast, the Ossimi breed showed a high affinity to a fat-tailed breed of Western Asia, suggesting a direct migration and no thin tail ancestors. The Saidi is unique as our analyses revealed its strong connection with thin-tailed Sudanese breeds.

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To understand the molecular and genetic mechanisms related to the litter size in one species of two different populations (high litter size and low litter size), we performed RNA-seq for the oocytes and granulosa cells (GCs) at different developmental stages of follicle, and identified the interaction of genes from both sides of follicle (oocyte and GCs) and the ligand-receptor pairs from these two sides. Our data were very comprehensive to uncover the difference between these two populations regarding the folliculogenesis. First, we identified a set of potential genes in oocyte and GCs as the marker genes which can be used to determine the goat fertility capability and ovarian reserve ability. The data showed that GRHPR, GPR84, CYB5A and ERAL1 were highly expressed in oocyte while JUNB, SCN2A, MEGE8, ZEB2, EGR1and PRRC2A were highly expressed in GCs. We found more functional genes were expressed in oocytes and GCs in high fertility group (HL) than that in low fertility group (LL). We uncovered that ligand-receptor pairs in Notch signaling pathway and transforming growth factor-β (TGF-β) superfamily pathways played important roles in goat folliculogenesis for the different fertility population. Moreover, we discovered that the correlations of the gene expression in oocytes and GCs at different stages in the two populations HL and LL were different, too. All the data reflected the gene expression landscape in oocytes and GCs which was correlated well with the fertility capability.