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Increased gene dosage for β - and κ -casein in transgenic cattle improves milk composition through complex effects

View Article: PubMed Central - PubMed

ABSTRACT

We have previously generated transgenic cattle with additional copies of bovine β- and κ casein genes. An initial characterisation of milk produced with a hormonally induced lactation from these transgenic cows showed an altered milk composition with elevated β-casein levels and twofold increased κ-casein content. Here we report the first in-depth characterisation of the composition of the enriched casein milk that was produced through a natural lactation. We have analyzed milk from the high expressing transgenic line TG3 for milk composition at early, peak, mid and late lactation. The introduction of additional β- and κ-casein genes resulted in the expected expression of the transgene derived proteins and an associated reduction in the size of the casein micelles. Expression of the transgenes was associated with complex changes in the expression levels of other milk proteins. Two other major milk components were affected, namely fat and micronutrients. In addition, the sialic acid content of the milk was increased. In contrast, the level of lactose remained unchanged. This novel milk with its substantially altered composition will provide insights into the regulatory processes synchronizing the synthesis and assembly of milk components, as well as production of potentially healthier milk with improved dairy processing characteristics.

No MeSH data available.


Casein micelle diameter in milk from transgenic and control cows.The size of the casein micelles was measured by photon correlation spectroscopy in whole milk (solid bars) and skim milk (open bars) produced in a natural lactation by three transgenic (TG3-1, -2, -3; black) and four wild type control (WT-1, -2, -3, -4; red) cows.
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f3: Casein micelle diameter in milk from transgenic and control cows.The size of the casein micelles was measured by photon correlation spectroscopy in whole milk (solid bars) and skim milk (open bars) produced in a natural lactation by three transgenic (TG3-1, -2, -3; black) and four wild type control (WT-1, -2, -3, -4; red) cows.

Mentions: According to models of casein micelle structure18 and transgenic mouse models overexpressing κ-casein1920, the concentration of κ-casein is inversely correlated with the size of the micelle. To assess whether this effect is also the case in cattle, we determined the size of the casein micelles for whole milk and skim milk samples derived from three TG3 cows and four control cows using photon correlation spectroscopy. As predicted, the higher κ-casein concentration in the TG3 milk resulted in smaller casein micelles in both, whole milk (P < 0.001) and skim milk (P < 0.005) (Fig. 3). The mean size of the protein particles in the TG3 milk samples were 119 ± 2.3 nm (mean ± standard error of the mean) in whole milk and 136 nm ± 7.7 in skim milk. The micelles present in TG3 milk were on average 85 nm (whole milk) and 70 nm (skim milk) smaller than that from wild type controls (204 ± 3.6 nm and 206 ± 3.4 nm, respectively), representing a size reduction to approximately 58% (whole milk) and 66% of the mean casein micelle size found in wild type milk.


Increased gene dosage for β - and κ -casein in transgenic cattle improves milk composition through complex effects
Casein micelle diameter in milk from transgenic and control cows.The size of the casein micelles was measured by photon correlation spectroscopy in whole milk (solid bars) and skim milk (open bars) produced in a natural lactation by three transgenic (TG3-1, -2, -3; black) and four wild type control (WT-1, -2, -3, -4; red) cows.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120311&req=5

f3: Casein micelle diameter in milk from transgenic and control cows.The size of the casein micelles was measured by photon correlation spectroscopy in whole milk (solid bars) and skim milk (open bars) produced in a natural lactation by three transgenic (TG3-1, -2, -3; black) and four wild type control (WT-1, -2, -3, -4; red) cows.
Mentions: According to models of casein micelle structure18 and transgenic mouse models overexpressing κ-casein1920, the concentration of κ-casein is inversely correlated with the size of the micelle. To assess whether this effect is also the case in cattle, we determined the size of the casein micelles for whole milk and skim milk samples derived from three TG3 cows and four control cows using photon correlation spectroscopy. As predicted, the higher κ-casein concentration in the TG3 milk resulted in smaller casein micelles in both, whole milk (P < 0.001) and skim milk (P < 0.005) (Fig. 3). The mean size of the protein particles in the TG3 milk samples were 119 ± 2.3 nm (mean ± standard error of the mean) in whole milk and 136 nm ± 7.7 in skim milk. The micelles present in TG3 milk were on average 85 nm (whole milk) and 70 nm (skim milk) smaller than that from wild type controls (204 ± 3.6 nm and 206 ± 3.4 nm, respectively), representing a size reduction to approximately 58% (whole milk) and 66% of the mean casein micelle size found in wild type milk.

View Article: PubMed Central - PubMed

ABSTRACT

We have previously generated transgenic cattle with additional copies of bovine &beta;- and &kappa; casein genes. An initial characterisation of milk produced with a hormonally induced lactation from these transgenic cows showed an altered milk composition with elevated &beta;-casein levels and twofold increased &kappa;-casein content. Here we report the first in-depth characterisation of the composition of the enriched casein milk that was produced through a natural lactation. We have analyzed milk from the high expressing transgenic line TG3 for milk composition at early, peak, mid and late lactation. The introduction of additional &beta;- and &kappa;-casein genes resulted in the expected expression of the transgene derived proteins and an associated reduction in the size of the casein micelles. Expression of the transgenes was associated with complex changes in the expression levels of other milk proteins. Two other major milk components were affected, namely fat and micronutrients. In addition, the sialic acid content of the milk was increased. In contrast, the level of lactose remained unchanged. This novel milk with its substantially altered composition will provide insights into the regulatory processes synchronizing the synthesis and assembly of milk components, as well as production of potentially healthier milk with improved dairy processing characteristics.

No MeSH data available.