Production of transgenic dairy goat expressing human α-lactalbumin by somatic cell nuclear transfer.

Production of human α-lactalbumin (hα-LA) transgenic cloned dairy goats has great potential in improving the nutritional value and perhaps increasing the yield of dairy goat milk. Here, a mammary-specific expression vector 5A, harboring goat ß-lactoglobulin (ßLG) promoter, the hα-LA gene, neo(r) and EGFP dual markers, was constructed. Then, it was effectively transfected into goat mammary epithelial cells (GMECs) and the expression of hα-LA was investigated. Both the hα-LA transcript and protein were detected in the transfected GMECs after the induction of hormonal signals. In addition, the 5A vector was introduced into dairy goat fetal fibroblasts (transfection efficiency ≈60-70%) to prepare competent transgenic donor cells. A total of 121 transgenic fibroblast clones were isolated by 96-well cell culture plates and screened with nested-PCR amplification and EGFP fluorescence. After being frozen for 8 months, the transgenic cells still showed high viabilities, verifying their ability as donor cells. Dairy goat cloned embryos were produced from these hα-LA transgenic donor cells by somatic cell nuclear transfer (SCNT), and the rates of fusion, cleavage, and the development to blastocyst stages were 81.8, 84.4, and 20.0%, respectively. A total of 726 reconstructed embryos derived from the transgenic cells were transferred to 74 recipients and pregnancy was confirmed at 90 days in 12 goats. Of six female kids born, two carried hα-LA and the hα-LA protein was detected in their milk. This study provides an effective system to prepare SCNT donor cells and transgenic animals for human recombinant proteins.

Formula feeding skews immune cell composition toward adaptive immunity compared to breastfeeding.

The ontogeny of the immune system and the effect thereon by type of infant feeding is incompletely understood. We analyzed frequencies and composition of immune cells in blood of breastfed (BF) and formula-fed (FF) infants at 1.5, 4, and 6 mo of age. Three formulas with the same protein concentration but with varying levels of alpha-lactalbumin and caseinoglycomacropeptide were compared. Twenty-nine exclusively BF infants served as reference, and 17 infants in each formula group completed the study. Whole blood and PBMCs were analyzed by flow cytometry and immunoflow cytometry, respectively. Leukocyte count of BF infants increased with time due to increased frequency of neutrophils. Lymphocyte count was high at 1.5 mo and was unchanged over time, as were the relative proportions of CD4+ alphabetaT cells, CD8+ alphabetaT cells, B cells, NK cells, and gammadeltaT cells. Most CD45R0+CD3+ cells were HLA-DR- and hence memory cells. Compared with breastfeeding, formula feeding resulted in a significant decrease in proportion of NK cells, but a significant increase in naive CD4+ alphabetaT cells and an elevated CD4-to-CD8 ratio, that is, 3.3 in the combined FF groups compared with 2.6 in the BF group. No significant differences were found between the three groups of FF infants. In conclusion, blood cells of lymphoid lineage did not change significantly in frequencies or composition from 1.5 to 6 mo of age in BF infants. In contrast, FF infants displayed an ongoing maturation of adaptive immunity cells and a delayed recruitment of innate immunity cells as compared with BF infants.

Lactose synthetase activity in mouse mammary glands is controlled by thyroid hormones.

Epithelial cells in explants from the mammary glands of euthyroid mature virgin mice are proliferatively dormant. They must undergo DNA synthesis and traverse the cell cycle in vitro before they are able to differentiate fully in response to insulin, hydrocortisone, and prolactin, and synthesize enzymatically active alpha-lactalbumin (measured as lactose synthetase activity). In contrast, glands from hyperthyroid mature virgin mice do not require DNA synthesis in vitro to differentiate. Explants from the euthyroid virgin tissue overcome their dependence on DNA synthesis when 10(-9) M 3,5,3'-triiodo-L-thyronine is added directly to the cultures in addition to the other three hormones. Explants from involuted mammary glands from euthyroid primiparous mice do not require DNA synthesis in vitro to make the milk protein even though they, like explants from mature euthyroid virgin tissue, are proliferatively dormant and do not contain detectable lactose synthetase activity in vivo. Glands from primiparous animals made mildly hypothyroid by ingestion of 0.1% thiouracil in drinking water during 7 wk of involution remain morphologically indistinguishable from glands of their euthyroid counterparts. However, explants from the glands of these hypothyroid animals revert to a state of dependence on DNA synthesis to differentiate functionally. These observations suggest that the dependence on DNA synthesis and cell cycle traversal for hormonal induction of lactose synthetase activity in the mouse mammary gland is controlled by thyroid hormones.

Alpha-lactalbumin production in human mammary carcinoma.

Alpha-Lactalbumin was isolated from mature human milk and utilized as an immunogen in rabbits. A radioimmunoassay was developed that was capable of detecting nanogram quantities of the antigen. Alpha-Lactalbumin synthesis was detected in human breast cancer cells (MCF-7) cultivated as a continuous cell line in vitro. Other human carcinoma epithelial cell lines (throat and cervix) failed to react in this assay. The ability to synthesize alpha-lactalbumin by breast carcinoma cells appeared to be independent of the addition of prolactin to the culture medium.

alpha-Lactalbumin-casein induction in virgin mouse mammary explants: dose-dependent differential action of cortisol.

The interplay of insulin, cortisol, and prolactin induces synthesis of casein and alpha-lactalbumin in cultured mammary explants from mature virgin mice. A striking difference has been found between the optimal concentrations of cortisol required for maximal induction of the two milk proteins in vitro: 3 x 10(-8) molar for alpha-lactalbumin and 3 x 10(-6) molar for casein. Moreover, 10(-7) to 10(-5) molar cortisol caused progressive inhibition of alpha-lactalbumin accumulation. Such differential actions of cortisol may partly account for the asynchronous synthesis of the two proteins during pregnancy.

Spermidine in hormone-dependent differentiation of mammary gland in vitro.

Stiulation of milk-protein synthesis in mouse mammary epithelium in vitro requires insulin, hydrocortisone, and prolactin. The requirement for hydrocortisone can be replaced by spermidine. The possibility that spermidine mediates the effect of glucocorticoid is also supported by the observation that the cellular spermidine concentration increases before the accelerated synthesis of casein and alpha-lactalbumin.

Mesenchyme-dependent morphogenesis and epithelium-specific cytodifferentiation in mouse mammary gland.

Isografts of heterotypic recombinants of embryonic mammary epithelium with salivary mesenchyme undergo development morphogenetically resembling that of salivary gland. However, cytodifferentiation of the epithelium is like that of mammary gland. In lactating hosts these isografts respond to endogenous hormonal stimulation and synthesize a milk protein, alpha-lactalbumin.

Characterizing transgene inheritance.

The analysis of transgene inheritance is an important step in the molecular and genetic characterization of transgenes. In this manuscript, two approaches to characterize the inheritance of transgenes are described. The first approach is based on the expression of the transgene phenotype and the second is based on the analysis of transgene DNA. Instructions on how to make crosses and develop breeding populations are outlined and the importance of these breeding populations in the analysis of transgene inheritance is explained. The number of individuals needed to determine segregation ratios and the statistic used to test these ratios are described. Examples of inheritance patterns that deviate from known expectations are provided and the possible causes of these deviations are discussed.

Use of double-replacement gene targeting to replace the murine alpha-lactalbumin gene with its human counterpart in embryonic stem cells and mice.

The mouse alpha-lactalbumin gene has been replaced with the human gene by two consecutive rounds of gene targeting in hypoxanthine phosphoribosyltransferase (HPRT)-deficient feeder-independent murine embryonic stem (ES) cells. One mouse alpha-lactalbumin allele was first replaced by an HPRT minigene which was in turn replaced by human alpha-lactalbumin. The end result is a clean exchange of defined DNA fragments with no other DNA remaining at the target locus. Targeted ES cells at each stage remained capable of contributing efficiently to the germ line of chimeric animals. Double replacement using HPRT-deficient ES cells and the HPRT selection system is therefore a powerful and flexible method of targeting specific alterations to animal genes. A typical strategy for future use would be to generate a null mutation which could then be used to produce multiple second-step alterations at the same locus.

alpha-Lactalbumin content of rat mammary carcinomas and the effect of pituitary stimulation.

Primary mammary carcinomas induced in nonlactating rats by 7,12-dimethylbenz(alpha)anthracene or methylnitrosourea contained alpha-lactalbumin (alphaLA) in quantities equal to or less than 10% of the amounts found in the parenchyma of the 5-day lactating gland. Only two of five transplantable mammary carcinomas contained alphaLA when growing in rats without hormonal stimulation. Hormonal stimulation maintained by transplantation into lactating females for 146 generations (65 months) failed to induce alphaLA production in dimethylbenz(alpha)anthracene no.1 transplantable mammary carcinoma. Transplantation of a pituitary gland under the kidney capsule of the host (a) increased alphaLA content of primary dimethylbenz(alpha)anthracene-induced mammary carcinomas, (b) reduced alphaLA content of primary methylnitrosourea-induced mammary carcinomas, and (c) was unable to modify the alphaLA levels in five transplantable mammary carcinomas.

Differential regulation of alpha-lactalbumin and casein messenger RNA's in mammary tissue.

Rat caseins were characterized with respect to moleculare weight and carbohydrate and amino acid content. Messenger RNA was extracted from rat mammary glands at 5, 10, 15, and 20 days of pregnancy and at 2, 8, and 15 days of lactation and translated in a wheat germ cell-free system. Nascent [3H]casein and alpha-[3H]actalbumin were precipitated separately with specific antibodies and identified by their mobilities on sodium dodecyl sulfate:acrylamide gels and by competition with unlabeled casein and alpha-lactalbumin, respectively. Casein messenger rose continuously from Day 5 of pregnancy to Day 15 of lactation. In contrast, alpha-lactalbumin messenger RNA levels remained low during pregnancy but rose markedly during lactation.

Effect of prolactin on lactalbumin production by normal and malignant human breast tissue in organ culture.

To determine whether lactalbumin production by normal and neoplastic human mammary tissue is under the same control, the effect of prolactin treatment was studied in organ culture. Of 9 premenopausal normal breast samples, 6 produced lactalbumin in culture, and all 6 responded to prolactin treatment over 4 days. One biopsy of pregnant breast tested also responded to prolactin treatment, producing 200 times more lactalbumin in culture than did normal breast. Two of 4 normal postmenopausal biopsies produced lactalbumin, and one increased synthesis and release after prolonged exposure to prolactin. Of 10 scirrhous carcinomas, 6 produced lactalbumin, but none responded to prolactin treatment. In 2 premenopausal patients, normal breast tissue responded to different concentrations of prolactin, which were without effect on malignant tissue from the same breast. In summary, lactalbumin production in the samples that we have studied can be stimulated in normal but not in malignant breast tissue. This may indicate an absence or deficiency of prolactin receptors in malignant tissue.

Casein and alpha-lactalbumin messenger RNA in experimental breast cancer.

A transplantable rat mammary carcinoma (R3230AC) was previously shown to contain prolactin receptors. Our objective was to determine whether these receptors were functional by measuring specific markers of prolactin action: casein and alpha-lactalbumin (alphaLA) messenger RNA's (mRNA's). Total RNA exacts were translated in a wheat germ cell-free system. Newly synthesized 3H-casein and 3H-alphaLA were separately precipitated with specific antibodies and identified by their mobilities on sodium dodecyl sulfate-acrylamide gels and by competition with nonradioactive casein and alphaLA. Casein and alphaLA mRNA's were both present in unstimulated tumors grown in virgin rats. Casein mRNA but not alphaLA mRNA was markedly stimulated by injections of exogenous ovine prolactin or perphenazine, an agent that stimulates endogenous prolactin. This response was selective in that total mRNA was not significantly altered by prolactin.

Establishment and characterization of three new continuous cell lines derived from human breast carcinomas.

Three continuous lines of mammary tumor cells (ZR-75-1, ZR-75-27, and ZR-75-30) have been established from malignant effusions of two women with breast cancer. Differentiated properties expressed by each cell line include: (a) epithelial morphology (by light and electron microscopy) resembling that of the parental tumors; (b) presence of receptors for estrogen and other steroid hormones; and (c) growth responsiveness to estrogen and/or progesterone. All three cell lines possess human karyotypes that differ from one another in modal chromosome number as well as in characteristic marker chromosomes. Two of the cultures (ZR-75-27 and ZR-75-30), although derived from the same patient, have stable differences in their karyotypes.

Human breast carcinoma cells in continuous culture: a review.

A comprehensive listing of putative human breast carcinoma cell lines and the extent to which each has been characterized is presented. Criteria used to certify the human, mammary, and malignant origin of a cell line include: (a) a reliable histopathological diagnosis; (b) interspecies specificity established by human karyotype, isoenzyme profiles, and/or cell surface antigenicity; (c) intraspecies specificity, demonstrated by genetic evidence of a unique, human donor distinct from other cells including HeLa cells; and (d) organ specficity, supported by morphological evidence of epithelial structure and secretory activity, and especially by the expression of differentiated functions; these include presence of receptors for sex steroid hormones, hormone responsiveness, and production of milk proteins, fatty acids, or milk-specific antigens. Of the 47 cell lines for which data are here reported, 22 have been shown to be derived from human non-HeLa donors and to have epithelial morphology as revealed by light or electron microscopy. Differentiated function has been recorded for 19 cell lines. Additional human breast cancer cell lines have been reported, but characterization of some of these has been insufficient to judge the legitimacy of their predigrees. For others mammary origin is questionable. Six purported breast cell lines are in reality HeLa cells, and one is of nonhuman origin.

Difference between mammary epithelial cells from mature virgin and primiparous mice.

Mammary epithelial cells from mature virgin mice are similar to those from primiparous mice in several respects. However, there is one known difference. The cells from the mature virgin must traverse the cell cycle in order to become competent to make casein and enzymatically active alpha-lactalbumin in vitro; those from the primiparous animal can make these proteins without first traversing the cycle. In this regard, cells from human placental lactogen- and prolactin-treated mature virgins are, after involution, similar to those from primiparous mice. The developemental block in the cells from the mature virgin, imposed by preventing cell cycle traversal, has been partially delineated. It does not appear to reside at the levels of ultrastructural maturation or the formation of casein messenger RNA. Rather, the lesion is postranscriptional and may be at the level of translation, or posttranslational modification, or both.

Purification and characterization of mouse alpha-lactalbumin from lactating mammary glands.

The whey protein, alpha-lactalbumin, was purified from lactating mammary glands of mice at high yields. It exists as two major charge forms (pI values of 6.2 and 5.8) with similar molecular weights (approx. 14600). Antibodies prepared against these peptides precipitate newly synthesized and secreted alpha-lactalbumin from organ cultures of mid-pregnancy mammary glands. The antibody is specific for mouse alpha-lactalbumin as it does not react with mouse casein, mouse serum or purified bovine alpha-lactalbumin or galactosyl transferase. In addition, it blocks enzymatic activity of alpha-lactalbumin in mouse milk but has no effect on guinea pig or human milk. A very sensitive radioimmunoassay has been developed with this antibody which can detect alpha-lactalbumin levels as low as 0.25 ng.

Specificity and mechanism of biphasic action of glucocorticoids on alpha-lactalbumin production by rat mammary gland explants.

RU26988 [11 beta, 17 beta-dihydroxy-17 alpha-(1-propynyl)androsta-1,4,6-trien-3-one], a specific type II (glucocorticoid) ligand with negligible affinity for type I (mineralocorticoid) receptors, increased alpha-lactalbumin production in mammary gland explants from midpregnant rats when cultured in vitro in the presence of insulin (5 micrograms/ml) and rat PRL (1 microgram/ml). The dose-response curve was biphasic, over a 3-300 nM dose range, with maximum at 3-10 nM, followed by a progressive decline toward or to control levels at 300 nM. A similar dose-response curve was obtained with another type II-specific ligand, RU28362 [11 beta, 17 beta-dihydroxy-6-methyl-17 alpha-(1-propynyl)androsta-1,4,6-trien-3-one], and with dexamethasone. This biphasic response had been previously reported for mouse mammary gland explants using cortisol, which binds to both type I and type II receptors. Our experiments, therefore, show that occupancy of type II receptors alone can be responsible for the stimulation at low steroid concentrations, followed by the decrease from peak levels observed at higher steroid concentrations. On the basis of these data, we propose a model to account for these findings, based on ligand binding to a single class of receptors and the putative existence of both turn-on and turn-off glucocorticoid regulatory elements in the nucleus.

Evidence that prolactin stimulates alpha-lactalbumin production in mannary tissues from premenarcheal rhesus monkeys.

PRL was found to stimulate marked increases in alpha-lactalbumin production in six of eight specimens of mammary tissue from premenarcheal rhesus monkeys, and a lesser increase was seen in a seventh. Even without added PRL, low concentrations of this milk protein (mean total alpha-lactalbumin production, 1.9 ng/dish) were released into the organ culture medium bathing these relatively immature tissues; most of the epithelial elements were ductal. Under similar conditions, significantly higher concentrations of alpha-lactalbumin (mean total production, 23.4 ng/dish) were released from tissues of sexually mature animals in which lobulo-alveolar elements were abundantly present in addition to ducts. When tissues from premenarcheal animals were exposed to ovine PRL, alpha-lactalbumin concentration in medium and tissue homogenates were increased significantly. Overall, mean total alpha-lactalbumin production rose to 12.9 (P less than 0.02) and 40.5 (P less than 0.02) ng/dish in response to 100 and 1000 ng/ml ovine PRL, respectively. In those cases in which both medium and tissue homogenates were analyzed, increases were parallel. These findings indicate that PRL has a lactogenic effect on mammary tissue from sexually immature and mature rhesus monkeys.

Effect of insulin-like growth factor I on deoxyribonucleic acid synthesis and galactopoiesis in bovine undifferentiated and lactating mammary tissue in vitro.

We have demonstrated that insulin-like growth factor I (IGF-I), at physiological concentrations, is a potent mitogen of bovine undifferentiated mammary epithelial cells cultured in collagen in serum-free medium. Its activity is independent of insulin, although at pharmacological concentrations insulin may substitute for IGF-I. The maximal [3H]thymidine incorporation stimulated by either IGF-I or insulin was only 25-40% of that in medium supplemented with 10% fetal calf serum (FCS) only. Epidermal growth factor (EGF) exhibited low mitogenic activity which was not synergistic with IGF-I in serum-free medium. IGF-I and EGF had low synergistic activity when added separately to 10% FCS-supplemented medium. Strong synergism (100% or more) was observed, however, when both factors were added simultaneously, indicating that their maximum mitogenic effect is dependent on a simultaneous presence of other factors existing in FCS. The galactopoietic effect of IGF-I was tested in organ culture of bovine lactating mammary gland. Neither fatty acid synthesis nor alpha-lactalbumin secretion was stimulated by IGF-I, even at 2000 ng/ml. These results indicate that, at least in our in vitro system, galactopoiesis is not affected by IGF-I.