Dynamics of recombinant hG-CSF in transgenic goat: preliminary study in the founder during hormonally induced lactation

Evaluation of the α-casein (CSN1S1) locus as a potential target for a site-specific transgene integration

Transgenic animals are an important tool in biotechnology, including the production of recombinant proteins in the milk. Traditionally, expression constructs are based on hybrid vectors bearing mammary gland specific regulatory elements from the α-casein (Csn1s1), β-casein (Csn2), whey acidic protein (WAP), or β-lactoglobulin (BLG) genes. Overexpression from the randomly integrated vectors typically provides high levels of expression, but has drawbacks due to unpredictable genome localization. CRISPR-Cas9 targeted transgene integration into the endogenous casein locus could alleviate the need for extensive animal screening to achieve high and reproducible expression levels. We decided to evaluate such a “precise” integration approach, placing the human granulocyte–macrophage colony-stimulating factor (hGMCSF) gene under control of the mouse endogenous alpha-S1-casein (Csn1s1) promoter. We designed two types of transgene integrations: a knock-in in the second exon of the Csn1s1 (INS-GM) and a full-size Csn1s1 replacement with hGMCSF (REP-GM) which was never tested before. The INS-GM approach demonstrated low transgene expression and milk protein levels (0.4% of Csn2 transcripts; 2–11 µg/ml hGMCSF). This was probably caused by the absence of the 3’-polyadenylation signal in the hGMCSF transgene. REP-GM animals displayed high transgene expression, reaching and slightly exceeding the level of the endogenous Csn1s1 (30–40% of Csn2 transcripts), but yielded less hGMCSF protein than expected (0.2–0.5 mg/ml vs 25 mg/ml of Csn1s1), indicating that translation of the protein is not optimal. Homozygous inserts leading to the Csn1s1 knock-out did not have any long standing effects on the animals’ health. Thus, in our experimental design, site-specific transgene integration into the casein locus did not provide any significant advantage over the overexpression approach.

Growth and reproductive traits of F1-generation transgenic goats for human granulocyte-colony stimulating factor

To ensure that animal welfare requirements and phenotypic characteristics of the newly produced transgenic lines are not compromised, an evaluation of all individuals is necessary. This can be inferred by the analysis of the growth and reproduction parameters. The present study was designed to determine the impact of the insertion of human granulocyte-colony stimulating factor (hG-CSF) transgene on growth and reproductive characteristics in first-generation (F1) goats from two transgenic lines. Bodyweight (BW) development (BW at birth, mean BW gain before weaning, BW at weaning, mean BW gain after weaning, BW at puberty), as well as reproductive parameters (age at puberty, ejaculate volume, concentration, total sperm per ejaculate, massal motility, progressive individual motility, major and minor defects) were similar (P > 0.05) between transgenic (T) and non-transgenic (NT) goats. Significant (P < 0.05) differences in mean (±s.d.) white blood cell count were observed between T and NT in first day of life (174.6 ± 14.7 × 103 and 15.0 ± 4.0 × 103 cells/µL), and during (66.8 ± 21.1 × 103 and 17.0 ± 4.6 × 103 cells/µL) and after (36.6 ± 4.0 × 103 and 15.5 ± 2.2 × 103 cells/µL) suckling, even though hG-CSF has not been detected in blood serum in any analysis. Although other cell counts were occasionally higher in T animals, differential counts showed that this difference was mainly due to an increased number of neutrophils, which represents 84.6%, 67.2% and 56.8% of total white blood cell count respectively, in the three time periods. Kidney and liver biochemical analyses indicated that all goats were healthy. Thus, it is possible to assume that all animals are normal and had no deleterious effects on either growth or reproductive parameters by the presence of transgene or as a consequence of leukocyte profile alteration.

MAMMARY BIOPSY IN INDUCED LACTATING GOATS: ASSESSMENT OF POST-BIOPSY MILK PROPERTIES AND ULTRASONOGRAPHIC APPEARANCE

Abstract The aim of this study was to evaluate the effects of mammary biopsy procedures on gland function of goats submitted to hormonal lactation. Ten female Caninde goats, at the age of around 3 years, were used, and lactation was induced by using estrogen, progesterone, and prednisolone. Ultrasonographic examinations of mammary gland, milking, and analysis of physicochemical properties of milk were performed immediately before (0 h) and 24, 48, and 72 h after each biopsy procedure. Surgical mammary gland biopsies were obtained at days 5 and 26 of the lactation. Even after drying initiation, all animals produced milk for five months. No abnormalities were observed on the ultrasonographic appearance of biopsied glands. All 20 biopsies were technically successful and any inflammation or infection was associated with biopsy procedures. Regarding the physicochemical properties and volumes of milk produced, no significant differences (P > 0.05) were observed between right and left glands nor in the comparison of the results from time 0 with 24, 48, and 72 h for biopsied teats. The mammary biopsy did not induce neither severe changes in production and physicochemical properties of the milk nor in ultrasonographic appearance of mammary gland of goats in hormonal lactation.

Phenotypic features of first-generation transgenic goats for human granulocyte-colony stimulation factor production in milk

Human granulocyte-colony stimulating factor (hG-CSF) is a hematopoietic growth factor used in neutropenic patients. It is produced in transgenic bacteria or cultured mammalian cells. As an alternative, we now show that hG-CSF can be expressed in the mammary gland of first-generation (F1) transgenic goats during induced lactation. Despite lower milk production, transgenic females presented a similar milk composition (fat, protein and lactose) when compared to non-transgenic (p > 0.05) ones. The mean concentration (±SD) of recombinant hG-CSF in milk during lactation was 360 ± 178 µg ml(-1). All clinical parameters, as well as kidney and liver function, indicated that F1 transgenic goats were healthy. Additionally, no ectopic hG-CSF expression was detected in studied tissues of F1 transgenic males. Thus, F1 hG-CSF-transgenic goats can express the recombinant protein in milk at quantities compatible with their use as bioreactors in a commercial-scale protein-production program.