CRISPR/Cas9-mediated tryptophan hydroxylase 1 knockout decreases calcium transportation in goat mammary epithelial cells

Successful editing and maintenance of lactogenic gene expression in primary bovine mammary epithelial cells

In vitro investigation of bovine lactation processes is limited by a lack of physiologically representative cell models. This deficiency is most evident through the minimal or absent expression of lactation-specific genes in cultured bovine mammary tissues. Primary bovine mammary epithelial cells (pbMECs) extracted from lactating mammary tissue and grown in culture initially express milk protein transcripts at relatively representative levels. However, expression drops dramatically after only three or four passages, which greatly reduces the utility of primary cells to model and further examine lactogenesis. To investigate the effects of alternate alleles in pbMECs including effects on transcription, we have developed methods to deliver CRISPR-Cas9 gene editing reagents to primary mammary cells, resulting in very high editing efficiencies. We have also found that culturing the cells on an imitation basement membrane composed of Matrigel, results in the restoration of a more representative lactogenic gene expression profile and the cells forming three-dimensional structures in vitro. Here, we present data from four pbMEC lines recovered from pregnant cows and detail the expression profile of five key milk synthesis genes in these MECs grown on Matrigel. Additionally, we describe an optimised method for preferentially selecting CRISPR-Cas9-edited cells conferring a knock-out of DGAT1, using fluorescence-activated cell sorting (FACS). The combination of these techniques facilitates the use of pbMECs as a model to investigate the effects of gene introgressions and genetic variation in lactating mammary tissue.

Increasing serotonin concentrations alter calcium metabolism in periparturient dairy goats

Due to the large amounts of calcium transferred to milk from mammary glands, periparturient dairy goats face challenges with calcium metabolism disorder and hypocalcemia. Serotonin (5-hydroxytryptamine, 5-HT), the product of 5-hydroxy-l-tryptophan (5-HTP) catalyzed by tryptophan hydroxylase 1, is a multifunctional monoamine thought to be a homeostatic regulator of the animal. The objective of the current study was to investigate the effects and underlying mechanisms of intramuscular 5-HTP injections on calcium homeostasis in the goat mammary glands. In the in vivo experiment, 30 multiparous Guanzhong dairy goats were randomly assigned to 2 groups, one group was injected with 5-HTP intramuscularly and the other group was injected with normal saline. From the first 10 d of the expected date for delivery, 5-HTP or saline was injected into goats through the shoulder muscle every morning before feeding, with a dose of 1 mg/kg per body weight. In the in vitro experiment, goat mammary epithelial cells (GMEC) were treated with 100 μM 5-HT for the evaluation of 5-HT in calcium transportation. The results demonstrated that 5-HTP treatment had no effect on the basic composition of colostrum (P > 0.05) but increased the serum 5-HT concentrations on days -5, -4, -3, and 5 relative to parturition (P < 0.05). The 5-HTP injection group had greater serum calcium concentration on day 4 and greater serum parathyroid hormone-related protein (PTHrP) on days -5, -4, -1, 3, 4, and 5 compared with the saline injection group (P < 0.05). It was further confirmed that 5-HT could increase intracellular calcium levels by increasing PTHrP and decreasing plasma membrane Ca2+-ATPases1 (PMCA1) in GMEC (P < 0.05). In conclusion, 5-HTP treatment in multiparous goats during the transition period from pregnancy to lactation is a feasible way to protect goats from calcium metabolism disorder.