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Simple Summary: To explore molecular regulation related to lactation during pregnancy, the mammary glands of pregnant Mongolian mares during lactation and non-lactation were sequenced and analyzed for differentially expressed genes. We screened milk protein-related genes (CSN1S1, CSN3, and LALBA), genes related to the lipid metabolism process (DGAT1, LEP, and LEPR), and genes closely related to lactation events (FAT1 and LTF), which can be used as candidate genes for selecting lactation traits in Mongolian mares. To investigate molecular regulation involved in lactation during pregnancy, this study focused on the transcriptomic profiles of mammary tissue from lactating and non-lactating Mongolian mares at the second month of gestation. A total of 4197 differentially expressed genes were identified by comparing mammary tissues from pregnant mares at two different states, including 1974 differentially expressed genes such as the milk protein-related genes a-s1-casein (CSN1S1), k-casein (CSN3), lactalbumin (LALBA), and lactoferrin (LTF), which were highly expressed in the lactating mares group, and overall, these differentially expressed genes were mainly associated with biological processes such as endoplasmic reticulum protein processing, the Toll-like receptor signaling pathway, steroid biosynthesis, cytokine–cytokine receptor interactions, and amino sugar and nucleotide glycolysis. These findings serve as a foundation for investigating the molecular underpinnings of lactation in pregnant equids. [ABSTRACT FROM AUTHOR]

The equine foetal ovary has some unique characteristics that differ from other animals, such as ovary hyperplasia and high oestrogen secretion, and inverted location of cortex and medulla present in adult mare. The ovarian cortex supports the process of folliculogenesis and development, the synthetics and expression of oestrogen; however, the character‐related molecular mechanisms and specific biological functions in equine foetal ovarian cortex are still poorly understood. To explore the associated regulatory networks and molecular events of equine foetal ovary during the hyperplasia stage, we analysed the transcriptomic differences between the equine second‐trimester foetal ovarian cortex and adult ovarian cortex by RNA‐seq. There were 6334 differentially expressed genes (DEGs) present in foetal vs. adult, of which 3234 and 3100 DEGs were upregulated and downregulated, respectively. GO and KEGG were used for functional and pathway enrichment analysis of the DEGs. In particular, we found that some DEGs with high fold changes were related to steroid production and metabolism, such as CYP11A1, CYP17A1, LDLR, STAR and SCARB1, which were in line with the efficient oestrogen production in the equine foetal ovary. The transcriptome profile revealed the functional and developmental characteristics and gene expression patten of the ovarian cortex in the foetal and adult stages of the mare. Our study provides new insights into the molecular mechanism of equine second‐trimester foetal ovarian development through transcriptome analysis and provides insights for improving care or treatment for the pregnant mare and the foetus. [ABSTRACT FROM AUTHOR]

Abstract Satellite cells are an important cellular model for studying muscle growth and development and mammalian locomotion-related molecular mechanisms. In this study, we investigated the effects of voltage, pulse duration, and DNA dosage on horse skeletal muscle satellite cells’ electroporation transfection efficiency using the eukaryotic expression plasmid Td Tomato-C1 (5.5 kb) encoding the red fluorescent protein gene mainly based on fluorescence-positive cell rate and cell survival rate. By comparison of different voltages, pulse durations, and DNA doses, horse skeletal muscle satellite cells have nearly 80% transfection efficiency under the condition of voltage 120 V, DNA dosage 7 µg/ml, and pulse duration 30 ms. This optimized electroporation condition would facilitate the application of horse skeletal muscle satellite cells in genetic studies of muscle function and related diseases. [ABSTRACT FROM AUTHOR]

Satellite cells are an important cellular model for studying muscle growth and development and mammalian locomotion-related molecular mechanisms. In this study, we investigated the effects of voltage, pulse duration, and DNA dosage on horse skeletal muscle satellite cells' electroporation transfection efficiency using the eukaryotic expression plasmid Td Tomato-C1 (5.5 kb) encoding the red fluorescent protein gene mainly based on fluorescence-positive cell rate and cell survival rate. By comparison of different voltages, pulse durations, and DNA doses, horse skeletal muscle satellite cells have nearly 80% transfection efficiency under the condition of voltage 120 V, DNA dosage 7 µg/ml, and pulse duration 30 ms. This optimized electroporation condition would facilitate the application of horse skeletal muscle satellite cells in genetic studies of muscle function and related diseases.

To investigate molecular regulation involved in lactation during pregnancy, this study focused on the transcriptomic profiles of mammary tissue from lactating and non-lactating Mongolian mares at the second month of gestation. A total of 4197 differentially expressed genes were identified by comparing mammary tissues from pregnant mares at two different states, including 1974 differentially expressed genes such as the milk protein-related genes a-s1-casein ( CSN1S1 ), k-casein ( CSN3 ), lactalbumin ( LALBA ), and lactoferrin ( LTF ), which were highly expressed in the lactating mares group, and overall, these differentially expressed genes were mainly associated with biological processes such as endoplasmic reticulum protein processing, the Toll-like receptor signaling pathway, steroid biosynthesis, cytokine-cytokine receptor interactions, and amino sugar and nucleotide glycolysis. These findings serve as a foundation for investigating the molecular underpinnings of lactation in pregnant equids.

The preparation of paraffin sections is an important experimental technique in animal histological research, and key factors that determine the quality of a section include the dehydration time, waxing time, and drying temperature of the paraffin section. Paraffin sections obtained from testis tissue of adult horses exhibited higher quality with clear tissue structure and complete cell morphology after they underwent gradient dehydration for 6 hours, were immersed in wax for 60 minutes, and were dried in a 75-degree oven for 15 minutes. The detailed, optimized procedures that are developed in the current study may simplify histological experiments and research on equine testes., (©The Author(s) 2024. Open Access. This article is licensed under a Creative Commons CC-BY International License.)