Evidence for the Tf locus being associated with an early lethal factor in a strain of pigs

The frequencies of three co-dominant alleles Tf ^A, Tf ^B and Tf ^c controlling the serum transferrin locus in native and exotic breeds of pig in the United Kingdom are shown. Matings between different transferrin genotypes and segregation of the transferrin alleles in piglets from 131 litters are also recorded.
In eleven litters from matings within a closely related group of animals heterozygous for the Tf ^c allele, no offspring of the Tf ^c/ Tf ^c genotype were born. Matings between heterozygous related boars believed to be carrying a lethal factor linked to the Tf locus and heterozygous unrelated sows of the Saddleback breed, resulted in offspring of the Tf ^c/ Tf ^c genotype being born.
An excess of heterozygote genotypes was found in all litters from matings between animals heterozygous for the Tf ^c allele. In all these litters the average litter size was 0.5 piglets less per litter than the average for all other litters studied. For the eleven litters from matings involving closely related animals heterozygous for the Tf ^c allele, the average litter size was 1.4 piglets less per litter than the average for all other litters.
The possibility of an early lethal factor being linked to the Tf locus in this family of pigs is discussed.     

Two new sheep transferrin variants and the effect of neuraminidase

Transferrin phenotypes were determined in six breeds of sheep by starch gel electrophoresis. Two new variants, Tf H_Czech and Tf K_Czech, were found and some evidence of their genetic control was obtained. Tf H_Czeeh was detected only in Sumava sheep; it has an intermediate mobility between Tf A and Tf B. Tf K_Czech was found only in Tsigais; it was localized between Tf B and Tf C. The frequencies of corresponding alleles were very low.
Individual transferrin variants (I, A, H_Czech, B, K_czech, C, D, E, and P) were treated with neuraminidase. Electrophoretic mobility of the strong band was decreased by two steps in each case. It suggests that in the strong Tf band two sialic acid residues are accessible to the enzyme.     

Studies on the transferrins of goats. 3. Evidence for a third transferrin allele

A new allele Tf ^c in serum transferrin of goats is postulated. It was considered that serum transferrins in goats classified into six phenotypes are genetically controlled by three codominant alleles, Tf ^A, Tf ^B and Tf ^c. Frequencies of Tf ^c were low in native goats in Korea, Philipines and Thailand, and this allele is yet to be observed in other breeds of goats.     

Frequencies of transferrin types in various breeds of domestic dogs

Plasma transferrin (Tf) types in dogs were studied by a method of horizontal polyacrylamide gel electrophoresis with a 10 % separation gel and a discontinuous buffer system (Tris-citrate-borate, pH 9.0). Samples were analysed from 1127 dogs belonging to 60 different breeds. Tf^B and Tf^c alleles, each in considerably high frequency, were observed in most of the breeds. Tf^A with relatively lower frequency was observed in Beagle, Cocker Spaniel, Doberman Pinscher, German Shepherd, German Shorthaired Pointer, Old Danish Pointer and Poodle. Two rare Tf alleles, Tf^D and the other designated as Tf^E, were observed only in Cocker Spaniel and in Poodle respectively. Basenji (44 samples) and Small Münsterlander (17 samples) showed the highest frequency (0.97) for Tf^C allele while Carelian Bear Dog (19 samples) showed the highest frequency (0.97) for Tf^B allele. In the total material, the frequencies of Tf alleles A, B, C, D and E were found to be 0.0182, 0.5075, 0.4716, 0.0009 and 0.0018 respectively. By using the observed and expected numbers of Tf heterozygotes, the average inbreeding coefficient (F) within breeds was estimated to be 0.14. Six samples of wolf (Canis lupus L.) studied seemed to be of Tf B type. The present study, along with earlier reports, showed that some of the plasma proteins and enzymes (albumin, transferrin, eserine resistant esterase) exhibit considerably more polymorphism than that reported for hemoglobin and some of the red cell and tissue enzymes in the domestic dog.     

Indispensability of Iron for the Growth of Cultured Chick Cells

In order to clarify the role of iron in the growth promoting effect of transferrin (Tf), the effects of the following substances were examined in cultured chick skeletal myogenic cells: transition metal ions (Fe²⁺, Fe³⁺, Cr³⁺, Cu²⁺, Mn²⁺, Co²⁺, Cd²⁺, Zn²⁺ and Ni²⁺), Tf complexes with these metals and metal-free apoTf.
The cells did not grow well when incubated in a culture medium composed of Eagle's minimum essential medium and horse serum. But they grew well in the presence of Fe²⁺ or Fe³⁺ (10–100 μM) or iron-bound Tf (10–500 nM) in the medium. None of the transition metal ions other than iron was effective. Neither apoTf nor Tf complexes with these metals showed the growth promoting effect. The generality of the requirement of iron for cell growth was ascertained in the primary culture of other types of chick embryonic cells: fibroblasts, cardiac myocytes, retinal pigment cells and spinal nerve cells.
The results show that iron is one of the indispensable substances for cell growth and suggest that Tf protein plays a role in facilitating the transport of iron into the cells.     

Transferrin Receptor on Chick Fibroblast Cell Surface and the Binding Affinity in Relevance to the Growth Promoting Activity of Transferrin

We examined the transferrin (Tf) receptor of chick skin fibroblasts using chick ¹²⁵I-Tf. When the cells were incubated with ¹²⁵I-Tf on ice, most of the cell-associated ¹²⁵I-Tf was found on the cell surface; on the other hand, a large part of it was located inside the cells when incubated at 37°C. By equilibrium binding assay, the number of Tf receptors per cell was determined as 6.7 × 10³. Dissociation constant was estimated to be 2.6 × 10⁻⁸ M.
The binding of ¹²⁵I-Tf was competitively inhibited by the addition of chick unlabeled Tf. Weaker inhibition was observed when bovine Tf was used as a competitor. Horse Tf had no effect on the binding of chick Tf. This agrees well qualitatively with chick cell growth-promoting activites of these Tfs.
Removal of Fe from Tf affected the affinity for its receptors. About 5- to 10-fold higher concentrations of chick apo–Tf was needed to achieve the same degree of inhibition of ¹²⁵I-Tf binding as that made by chick Fe-Tf.     

Transferrin types and reproduction in sheep

Transferrin types were determined for flocks of Finnish Landrace, Clun Forest, Soay and Merino sheep and gene frequencies were calculated. Analysis of ratios of transferrin types in segregating matings of Finnish Landrace and Clun Forest revealed a significant excess of heterozygotes in matings of heterozygous rams with heterozygous and with homozygous ewes. In Finnish Landrace, matings of sheep homozygous for Tf ^c to those heterozygous for Tf ^C gave a significant excess of homozygous male lambs and heterozygous female lambs. Finnish Landrace ewes of transferrin type BD had smaller litters than ewes of other types.     

Partial characterization of horse transferrin heterogeneity with respect to the atypical type, Tf C

In starch gel electrophoresis of horse sera each transferrin variant is formed by a strong anodal band and a weaker cathodal band. An 'atypical' variant, Tf C, has two zones of about equal intensity. Family data show that Tf C is genetically controlled by an allele Tf C at the Tf locus. Frequencies of transferrin alleles in various horse breeds are also presented.
After isolation and fractionation of individual transferrin variants (Tf O, Tf D, Tf C) on DEAE-Sephad Summary ex, additional weak bands were detected. The two main zones of each variant were isolated in a pure state and treated with neuraminidase. In all three variants studied the electrophoretic mobility of the slower band (2a) was decreased in two steps, and the faster band (4b) in four steps. The mobilities of bands derived from the fast zone (4b) were slower than mobilities of corresponding bands derived from the slow zone (2a). These results suggest the presence of two sialic acid residues in the slow zone, and of four residues in the fast zone. Residual heterogeneity was independent of sialic acid.     

Genetic control and population survey of transferrin in the Japanese quail

Transferrin types in the Japanese quail Coturnix coturnix japonica are controlled by a single autosomal locus Tf with at least two codominant alleles Tf^B and Tf^c. The frequencies of Tf^B and Tf^c in a commercial population of the domestic quail were 1.00 and 0.00, respectively.
Previous studies demonstrated that in the domestic populations of the Japanese quail three electrophoretic patterns AB, B and BC existed in egg white conalbumin and that the electrophoretic variation of conalbumin occurred in parallel with that of serum transferrin. Furthermore, from the preliminary mating experiments the transferrin-conalbumin variation was proposed to be under the control of at least two codominant alleles 77^s and Tf^c at an autosomal locus (Kimura et al., 1977, 1978).
The present study was designed (1) to report a large amount of family data from three generations in order to support the previously published hypothesis on genetic control of electrophoretic patterns of transferrin, and (2) to survey the gene constitution of transferrin in a commercial population of the domestic quail.
Sera were added with iron, heated for 5 min at 65°C (Stratil, 1967), then were investigated by means of horizontal starch gel electrophoresis. Hydrolysed starch from Connaught Medical Laboratories, Toronto, was used. A discontinuous citrate/Tris/LiOH/borate buffer system (pH 8.0) of Ferguson & Wallace (1961) was employed. The gels were stained with Amido Black 10B.     

Blood protein polymorphism in the one-humped camel (Camelus dromedarius) in the Sudan

The blood protein polymorphism of serum albumin, haptoglobin, transferrin, ceruloplasmin and haemoglobin have been studied in 135 samples from one-humped Arabian camel (Camelus dromedarius) of the Sudan by starch gel electrophoresis. Only the serum albumin and haptoglobin systems exhibited polymorphism with the estimated frequencies of 0.0222, 0.2227 and 0.7773 for Alb^v, Hp¹Hp⁰respectively. The frequency of Hp was 0.0325. No electrophoretic variant was observed at transferrin, ceruloplasmin and haemoglobin loci in the camel. The activity of the ceruloplasmin of the camel sera was weak.     

Evidence for transferrin polymorphism in Spanish wild rabbits

Serum samples from 412 Spanish wild rabbits were analysed by starch and polyacrylamide gel electrophoresis. Three different transferrin (Tf) phenotypes (A, AB and B) were observed by both methods. The occurrence of two codominant alleles (TfA and TfB with frequencies of 0.89 and 0.11 respectively) at an autosomal locus (Tf) was supported by the population data on genetic equilibrium. Electrophoretic mobility differences between the Tf variants A and B could not be explained by differences in sialic acid or iron contents. Each of the two Tf variants were shown to have two sialic acid residues by neuraminidase treatment. These variants had similar affinities for iron, and iron binding did not lead to the conversion of one variant into the other.     

A new transferrin variant from Iran (Tf B-Iran): review of 36 variant alleles

A total of 2581 serum samples collected from five population groups of Iran was studied for electrophoretic variations of the transferrin (Tf). Besides the common phenotype Tf C the authors could observe 41 individuals with rare Tf types: CB1, CB2, CD1, CDChi, CD2. In addition to these Tf types two individuals with a new Tf B variant were observed. This new variant was found in the Dezfooli sample and was designated as Tf B-Iran. The electrophoretic position of this variant is described, and all the hitherto known Tf variants are reviewed.     

Nature of the heterogeneity within genetic variants of bovine serum transferrin

A comparison is made of the four main components of an homozygous variant (A or D₂, D₂) of bovine serum transferrin. These are designated I-IV in order of increasing mobility in electrophoresis at pH 7.5. Components I, II, HI and IV have 2,2,3 and 3 residues of sialic acid per transferrin molecule and appear to correspond to components 2a, 2b, 3a and 3b respectively of Stratil & Spooner (1971). The difference between components I and II and between III and IV does not reside in sialic acid differences. On the basis of peptide maps of reduced carboxami-domethylated components, urea-starch gel electrophoresis and quantitative sequence studies, it is concluded that components II and IV have a scission in the peptide chain. By homology with the sequence of MacGillivray et al. (1977) for human serum transferrin it is suggested that the scission occurs between residues 55 and 54 from the C-terminus and this portion of the chain has a 'molecular' weight of ca. 6000. The implications are briefly discussed.     

Polymorphism of the serum proteins of wild pigs

One hunderd and ninety five wild pigs from two different regions of Poland were investigated for transferrin, amylase and ceruloplasmin polymorphism. A new transferrin phenotype Tf PB was detected. This phenotype differed from Tf AB in the electrophoretic mobility of the more anodal transferrin. Tf P is assumed to be the product of a new allele Tf P at the Tf locus. Two amylase phenotypes Am 1–2 and Am 2 were observed. The Am 1 allele was absent from the pigs in the Poznan region. Only one ceruloplasmin phenotype, Cp B, was found.     

The pathways of endocytosed transferrin and secretory protein are connected in the trans-Golgi reticulum

We used a conjugate of transferrin and horseradish peroxidase (Tf/HRP) to label the intracellular transferrin receptor route in the human hepatoma cell line HepG2. The recycling kinetics of [125I]Tf/HRP were similar to those of unmodified [125I]Tf, implying identical routes for both ligands. 3,3'Diaminobenzidine (DAB)-cytochemistry was performed on post-nuclear supernatants of homogenates of cells which were incubated with both Tf/HRP and [125I]Tf, and caused two different effects: (a) the equilibrium density of [125I]Tf containing microsomes in a Percoll density gradient was increased, and (b) the amount of immunoprecipitable [125I]Tf from density-shifted lysed microsomes was only 20% of that of nonDAB treated microsomes. The whole biosynthetic route of alpha 1-antitrypsin (AT), a typical secretory glycoprotein in HepG2 cells, was labeled during a 60-min incubation with [35S]methionine. DAB cytochemistry was performed on post-nuclear supernatants of homogenates of cells which were also incubated with Tf/HRP. DAB cytochemistry caused approximately 40% of microsome- associated "complex" glycosylated [35S]alpha 1-antitrypsin ([35S]c-AT) to shift in a Percoll density gradient. Only part of the density shifted [35S]c-AT could be recovered by immunoprecipitation. A maximum effect was measured already after 10 min of Tf/HRP uptake. The density distribution of the "high mannose" glycosylated form of 35S-alpha 1- anti-trypsin [( 35S]hm-AT) was not affected by Tf/HRP. If in addition to Tf/HRP also an excess of non-conjugated transferrin was present in the medium, [35S]c-AT was not accessible for Tf/HRP, showing the involvement of the transferrin receptor (TfR) in the process. Furthermore, we show that if Tf/HRP and [35S]c-AT were located in different vesicles, the density distribution of [35S]c-AT was not affected by DAB-cytochemistry. Pulse-labeling with [35S]methionine was used to show that [35S]c-AT became accessible to endocytosed Tf/HRP minutes after acquirement of the complex configuration. A common intracellular localization of endocytosed Tf/HRP and secretory protein could be confirmed by immuno-electron microscopy: cryosections labeled with anti-albumin (protein A-colloidal gold) as well as DAB reaction product showed double-labeling in the trans-Golgi reticulum.     

Equine marker genes. Polymorphism for transferrin alleles, TfF1 and TfF2, in Thoroughbreds

The equine transferrin F variant is distinguishable into two types, F1 and F2, on alkaline polyacrylamide gel electrophoresis. Gene frequencies in 63 related Thoroughbreds are 0.39 and 0.19 for TfF¹TfF², respectively. In contrast the frequencies for these two alleles in 375 related Standardbreds is 0.00 and 0.59.     

Polymorphism and inheritance of serum esterases and β-globulins in the paradise fish (Macropodus opercularis; Anabantidae)

Electrophoretic variants of serum esterases and β-globulins in two subspecies of paradise fish ( Macropodus opercularis ) were studied. Four esterase loci ( Est-1, Est-2, Est-3 and Est-4 ), a single transferin ( Tf ) and another major β-globulin locus ( Bg ) were identified by segregational analysis. Est-3 seems to be a monomorphic. locus. Three alleles of Est-1 , two of Est-2 , two of Est-4 , four of Tf and two alleles of Bg were found in the laboratory population. None of these loci were closely linked. Electrophoretic patterns of F₁ hybrids confirmed the monomeric structures of each of the studied proteins. Allelic segregation at the Tf and Bg loci was normal in F₂ and backcross populations. In crosses of the two Macropodus subspecies there were deviations from Mendelian ratios because of missing recombinant esterase phenotypes. Each of these would have been homozygous Est-2^f/f . We suppose that Est-2^f/f causes lethality in the early phase of development, except in the Est-1^c/c, Est-2^f/f combination characteristic of the parental subspecies M.o. concolor .     

Polymorphism of the serum proteins of wild pigs

One hundred and ninety five wild pigs from two different regions of Poland were investigated for transferrin, amylase and ceruloplasmin polymorphism. A new tranferrin phenotype Tf PB was detected. This phenotype differed from Tf AB in the electrophoretic mobility of the more anodal transferrin. Tf P is assumed to be the product of a new allele Tf P at the Tf locus. Two amylase phenotypes Am 1-2 and Am 2 were observed. The Am 1 allele was absent from the pigs in the Poznan region. Only one ceruloplasmin phenotype, Cp B, was found.     

Characterization of the transferrin-iron uptake system in Neisseria meningitidis

Abstract The transferrin-iron uptake system of six Neisseria meningitidis strains was characterized using ¹²⁵I-transferrin in receptor assays and ⁵⁵Fe-loaded transferrin in uptake assays. Receptors for transferrin varied among the strains both in number (from 700 to 4700 receptors per cell) and in their affinity constants for the protein ( K _a ranged from 0.7×10⁷ to 4.0×10⁷ 1 mol⁻¹). Neither receptor numbers nor affinity constants were significantly different in carrier and invasive strains, although the K_a seem to be somewhat higher in the latter. Iron uptake from transferrin was also variable among the strains, but showed the same lack of correlation with their origin.     

Genetic variations in albumin and transferrin as species markers in plasma of Callithricidae

Albumin (Alb) and transferrin (Tf) polymorphism in plasma of Callithricidae was investigated by means of starch gel electrophoresis. In 52 blood samples of three species (Saguinus mystax, S. oedipus and S. labiatus), four Alb phenotypes (Alb 1, Alb 2, Alb 3 and Alb 2-3) and two Tf phenotypes (Tf 1 and Tf 2) were observed. No Alb variant was found in S. oedipus and S. mystax.