Biomedical subjects

D Portetelle

Publications and source records attributed to D Portetelle.

At least 37 records · Page 2Linked to original sources

PubMed1998

Conservative mutations in the immunosuppressive region of the bovine leukemia virus transmembrane protein affect fusion but not infectivity in vivo.

Many retroviruses, including bovine leukemia virus (BLV), contain a highly conserved region located about 40 amino acids downstream from the fusion peptide within the sequence of the external domain of the transmembrane (TM) protein. This region is notably thought to be involved in the presentation of the NH2-terminal peptide to allow cell fusion. By using hydrophobic cluster analysis and by analogy with the influenza A hemagglutinin structures, the core of the TM structure including this particular region was predicted to consist, in the BLV and other retroviral envelope proteins, of an alpha-helix followed by a loop region, both docked against a subsequent alpha-helix that forms a triple-stranded coiled coil. The loop region could undergo, as in hemagglutinin, a major refolding into an alpha-helix integrating the coiled coil structure and putting the fusion peptide to one tip of the molecule. Based on this model, we have identified amino acids that may be essential to the BLV TM structure, and a series of mutations were introduced in the BLV env gene of an infectious molecular clone. A first series of mutations was designed to disturb the coiled coil structure (substitutions with proline residues), whereas others would maintain the general TM structure. When expressed by Semliki Forest virus recombinants, all the mutated envelope proteins were stable and efficiently synthesized in baby hamster kidney cells. Both proline-substituted and conservative mutants were strongly affected in their capacity to fuse to CC81 indicator cells. In addition, it appeared that the integrity of the TM coiled coil structure is essential for envelope protein multimerization, as analyzed by metrizamide gradient centrifugation. Finally, to gain insight into the role of this coiled coil in the infectious potential of BLV in vivo, the mutated TM genes were introduced in an infectious and pathogenic molecular clone and injected into sheep. It appeared that only the conservative mutations (A60V and A64S) allowed maintenance of viral infectivity in vivo. Since these mutations destroyed the ability to induce syncytia, we conclude that efficient fusion capacity of the recombinant envelopes is not a prerequisite for the infectious potential of BLV in vivo. Viral propagation of these mutants was strongly affected in some of the infected sheep. However, the proviral loads within half of the infected animals (2 out of 2 for A60V and 1 out of 4 for A64S) were close to the wild-type levels. In these sheep, it thus appears that the A60V and A64S mutants propagate efficiently despite being unable to induce syncytia in cell culture.

Amino Acid Sequence↗

PubMed1998

Identification of YHR019 in Saccharomyces cerevisiae chromosome VIII as the gene for the cytosolic asparaginyl-tRNA synthetase.

Exploiting the asparagine auxotrophy of the Saccharomyces cerevisiae mutant strain 8556a, we have isolated the gene for the cytosolic asparaginyl-tRNA synthetase (AsnRS) of S. cerevisiae, by functional complementation of the mutation affecting this strain. The isolated gene could be identified to the open reading frame YHR019, called DED81, located on chromosome VIII. The mutant gene from the 8556a strain, asnrs-1, was amplified from genomic DNA by PCR. This gene contains a point mutation, leading to the replacement of a glycine residue by a serine in a region of the protein probably important for the asparaginyl-adenylate recognition. The protein encoded by YHR019 is very similar to cytosolic AsnRS from other eukaryotic sources. In a phylogenetic analysis based on AsnRS sequences from various organisms, the eukaryotic sequences were clustered. Expression of YHR019 in Escherichia coli demonstrated that a yeast AsnRS activity was produced. The recombinant enzyme was purified to homogeneity in three chromatography steps. We showed that the recombinant S. cerevisiae AsnRS was able to charge unfractionated yeast tRNA, but not E. coli tRNA, with asparagine.

Amino Acyl-tRNA Synthetases↗

PubMed1998

Phosphorylation of bovine leukemia virus Tax protein is required for in vitro transformation but not for transactivation.

The Tax proteins of the oncovirinae viruses are phosphorylated transcriptional activators that exhibit oncogenic potential. The role of phosphorylation in their functional activities remains unknown. As a model for the Human T-cell leukemia virus type I (HTLV-I), Bovine Leukemia Virus (BLV) permits the characterization of viral replication and leukemogenesis in vivo. Here, we show that the BLV Tax protein is phosphorylated on serine residues 106 and 293 both in insect and in mammalian cells. These sites can also be efficiently phosphorylated by the cdc2 and MAP kinases in vitro. Mutation of these residues does not affect the capacity of the Tax protein to function as a transactivator. Indeed, the Tax proteins mutated at one or both serines increase LTR-directed viral transcription at levels similar to those obtained with wild-type Tax in cell culture. Moreover, inhibition of Tax phosphorylation by W7, a calmodulin antagonist, does not alter its transactivation activity. Thus, phosphorylation on serines 106 and 293 is not required for transactivation by Tax. However, simultaneous substitution of both serines into alanine residues destroys the capacity of Tax to cooperate with the Ha-ras oncogene to transform primary rat embryo fibroblasts and induce tumors in nude mice. When the serines were replaced with aspartic acid residues, the oncogenic potential of Tax was maintained indicating that the negative charge rather than the phosphate group itself was required for Tax oncogenicity. Finally, to assess the role of the serine residues in vivo, recombinant viruses which express the Tax mutants were constructed and injected into sheep. It appeared that the mutated proviruses replicate at levels similar to the wild-type virus in vivo. We conclude that Tax phosphorylation is dispensable for transactivation and viral replication in vivo but is required for its oncogenic potential in vitro.

Animals↗

PubMed1998

Evaluation of the genetic variability of 23 bovine microsatellite markers in four Belgian cattle breeds.

The polymorphism of 23 microsatellites in the four main cattle breeds in Belgium (Holstein Friesian, Belgian Blue, Belgian Red Pied and East Flemish) was analysed. Heterozygosity, polymorphism information content, the effective number of alleles, exclusion probability and the probability of genotypic identity for two random individuals were calculated for all microsatellites and all breeds. The Belgian Blue breed is generally a little less polymorphic in comparison with the other three breeds. Estimates of the genetic distances between these breeds confirmed the widely accepted proposition that the Belgian Blue is the most genetically distinct of these breeds. The three other breeds are likely to become one population, given current breeding strategies. Exclusion probabilities in parentage control cases are > 0.9999 in all four breeds when all 23 microsatellites are used and > 0.98 with only the two most polymorphic multiplexes.

Animals↗

PubMed1997

The complete genome sequence of the gram-positive bacterium Bacillus subtilis.

Bacillus subtilis is the best-characterized member of the Gram-positive bacteria. Its genome of 4,214,810 base pairs comprises 4,100 protein-coding genes. Of these protein-coding genes, 53% are represented once, while a quarter of the genome corresponds to several gene families that have been greatly expanded by gene duplication, the largest family containing 77 putative ATP-binding transport proteins. In addition, a large proportion of the genetic capacity is devoted to the utilization of a variety of carbon sources, including many plant-derived molecules. The identification of five signal peptidase genes, as well as several genes for components of the secretion apparatus, is important given the capacity of Bacillus strains to secrete large amounts of industrially important enzymes. Many of the genes are involved in the synthesis of secondary metabolites, including antibiotics, that are more typically associated with Streptomyces species. The genome contains at least ten prophages or remnants of prophages, indicating that bacteriophage infection has played an important evolutionary role in horizontal gene transfer, in particular in the propagation of bacterial pathogenesis.

Bacillus subtilis↗

PubMed1997

Mitochondrial asparaginyl-tRNA synthetase is encoded by the yeast nuclear gene YCR24c.

One of the open reading frames located on yeast Saccharomyces cerevisiae chromosome III, YCR24c, appeared to code for a protein of unknown function, but the predicted sequence showed similarity with asparaginyl-tRNA synthetase from Escherichia coli, with 38% amino acid identity. There is a putative mitochondrial targeting signal at the N-terminus of the YCR24c product. Northern blot analysis of total RNA from a wild-type strain sigma1278b confirmed that YCR24c was transcribed. Disruption of the chromosomal copy of YCR24c in a respiratory-competent haploid cell induced a petite phenotype, but did not affect cell viability. This respiratory-defective phenotype is typical for a mutation in a nuclear gene that induces a non-functional mitochondrial protein synthesis system. The protein encoded by YCR24c was expressed in Escherichia coli in a histidine-tagged form and isolated. The enzyme aminoacylated unfractionated Escherichia coli tRNA with asparagine. These results identified YCR24c as the structural gene for yeast mitochondrial asparaginyl-tRNA synthetase.

Amino Acid Sequence↗

PubMed1997

The effect of food intake from two weeks of age to sexual maturity on plasma growth hormone, insulin-like growth factor-I, insulin-like growth factor-binding proteins, and thyroid hormones in female broiler breeder chickens.

Plasma concentrations of metabolic hormones were determined in broiler breeders fed on three quantitatively different food regimes in the period prior to sexual maturity. The first group was fed ad libitum, the second group was fed a restricted quantity of food, and the third group was restricted to obtain an intermediate body weight between those of the first two groups. In food-restricted birds, insulin-like growth factor-I (IGF-I) reached the highest plasma concentrations at 8 and 14 weeks of age in contrast with levels in the fully fed animals, in which only one maximum value was observed at 10 weeks. From 14 weeks on, IGF-I concentrations remained higher in the restricted groups compared to the ad libitum group. Three IGF-binding proteins with molecular masses of 28, 34, and 40.5 kDa were detected in the plasma of broiler breeders after Western ligand blotting. The concentrations of the 28- and 34-kDa IGF-binding protein bands showed an age-related pattern in all groups. The intensity of these bands was higher in the restricted groups compared to that of the bands for the fully fed animals. No significant differences between the groups could be observed in the intensity of the 40.5-kDa band. Food restriction resulted in higher plasma concentrations of GH and T4 compared with levels in the fully fed animals. T3 plasma concentrations were higher in the ad libitum fed group than in the restricted groups. In all groups, GH and T3 concentrations decreased with advancing age, whereas T4 increased during the same period. This is the first description of the effects of long-term food restriction prior to the onset of sexual maturity on circulating levels of hormones of the somatotrophic and the thyrotrophic axes in female broiler breeders. The interrelationship between GH, IGF-I, IGFBPs, and thyroid hormone concentrations and differences in subsequent reproductive performance of differently fed broiler breeders requires further investigation.

Aging↗

PubMed1997

Relationships of growth hormone gene and milk protein polymorphisms to milk production traits in Simmental cattle.

The importance of milk proteins and the positive effect of administration of growth hormone (GH) on milk production, and the presence in some dairy cattle lines of greater GH concentrations prompted us to examine the presence of restriction fragment length polymorphism at the GH gene using the restriction enzyme TaqI and to investigate associations between this polymorphism in Simmental cows and bulls, as well as milk protein variants in Simmental cows, and milk production traits. Blood and milk were sampled from 279 Italian Simmental cows and semen was collected from 148 bulls of the same breed. Two fragment bands, denoted A and B, of 6200 and 5200 bp respectively, were examined and three patterns, AA, AB and BB, were found in both animal samples. All variants previously reported in other studies, for kappa, beta, and alpha s1-caseins, and beta-lactoglobulin, were found in the cows' samples. For the cows' samples, a BLUP (Best Linear Unbiased Predictor) analysis of results was performed using a REML (Restricted Maximum Likelihood) program and known heritabilities, whereas for bulls we have performed a General Linear Model analysis. The effect of GH gene polymorphism, using TaqI restriction enzyme, on milk production traits was not significant, but bulls of BB pattern had a higher breeding value for milk yield than AA bulls (P < 0.05). For the kappa-casein genotypic effects, cows of AB genotype gave milk with 1.53 +/- 0.70 g/kg less fat than cows of AA genotype. In addition, breeding values for milk protein content were significantly higher in BB bulls, with 0.87 +/- 0.32 and 0.71 +/- 0.34 g/kg more milk protein than AA and AB bulls respectively. Thus, our results revealed a GH gene polymorphism and indicated significant effects of milk protein polymorphisms on milk production traits in the Italian Simmental breed.

Animals↗

PubMed1997

The major homology region of bovine leukaemia virus p24gag is required for virus infectivity in vivo.

In order to gain insight into the role of the major homology region (MHR) in the infectious potential of bovine leukaemia virus (BLV), mutations were introduced into the capsid gene of an infectious molecular clone. A provirus that was designed to contain only a slightly modified version of the MHR (substitution of phenylalanine 147 with a tyrosine) was still infectious in vivo. Furthermore, the provirus loads were not significantly different from those obtained with a wild-type virus. A second mutant was designed to analyse a mild modification of the MHR at the level of arginine 150. The substitution of this residue with a lysine completely destroyed the infectious potential of the recombinant virus. Finally, a third mutant that was deleted in the MHR region was unable to infect the host. Thus it appears that the integrity of the MHR domain is essential for BLV infectivity in vivo.

Amino Acid Sequence↗

PubMed1997

Both wild-type and strongly attenuated bovine leukemia viruses protect peripheral blood mononuclear cells from apoptosis.

Bovine leukemia virus (BLV) and the human T-cell leukemia viruses belong to the same subfamily of oncoviruses. Although much attention has focused on the mechanisms of cell proliferation and transformation by these viruses, experiments on the apoptotic process have yielded conflicting data in in vitro cell culture. Experimental infection of sheep with BLV proviruses offers the opportunity to analyze apoptosis in vivo. Here, we show that BLV-infected peripheral mononuclear cells, cultivated ex vivo, are protected from spontaneous programmed cell death. Moreover, the virus is able to specifically interfere with the apoptotic program of infected B lymphocytes. Strongly attenuated mutant proviruses that harbor deletions in the G4 and/or R3 genes also decrease the global susceptibility to apoptosis at levels similar to those obtained with the wild-type virus. In addition, cell culture supernatants from wild-type and mutant viruses can prevent uninfected cells from undergoing programmed cell death. These observations demonstrate that the R3 and G4 genes are not required to maintain both direct and indirect protection against apoptosis. They also imply that the level of programmed cell death observed ex vivo is independent of the amounts of proviruses in the animals. The failure of these cells to undergo apoptosis might be related to the pathogenesis induced by BLV.

Animals↗

PubMed1997

Fusion of bovine leukemia virus with target cells monitored by R18 fluorescence and PCR assays.

PCR and R18 fluorescence dequenching assays have been combined to monitor the kinetics of fusion of bovine leukemia virus with target cells (CC81, OVK, or Raji). Antibodies raised against gp51 allow us to demonstrate that not only the hydrophobic N-terminal domain of the transmembrane glycoprotein gp30 but also specific domains of gp51 (amino acids 39 to 103) are involved in bovine leukemia virus-cell fusion.

Animals↗

PubMed1997

Polyclonal bovine sera but not virus-neutralizing monoclonal antibodies block bovine leukemia virus (BLV) gp51 binding to recombinant BLV receptor BLVRcp1.

Bovine leukemia virus (BLV), a transactivating lymphotropic retrovirus, is the etiologic agent of enzootic lymphosarcoma or leukemia in cattle. Sera from BLV-infected animals possess high BLV-neutralizing antibody titres. The availability of the recombinant BLV receptor candidate, BLVRcp1, allowed us to determine a mechanism of virus neutralization by polyclonal sera and monoclonal antibodies (MAbs). Bovine sera from animals naturally infected with BLV blocked gp51 binding to recombinant BLVRcp1. In contrast, virus-neutralizing MAbs specific for gp51 F, G, and H epitopes did not prevent gp51-receptor attachment. Furthermore, gp51 neutralization epitopes F, G, and H were accessible to antibodies following gp51 attachment to BLVRcp1. This finding implies that virus neutralization by MAbs to defined BLV gp51 epitopes can occur subsequent to virus engagement of the receptor while polyclonal sera can specifically block virus attachment to the receptor. In conclusion, these data suggest that cell infection by BLV is a multistep process requiring receptor binding (inhibited by polyclonal sera) followed by a second, postbinding event(s) at the cell membrane (inhibited by anti-gp51 MAbs).

3T3 Cells↗

PubMed1997

Pit-1 gene polymorphism, milk yield, and conformation traits for Italian Holstein-Friesian bulls.

The growth hormone factor-1/pituitary-specific transcription factor Pit-1 is responsible for the expression of growth hormone in mammals. Mutations in Pit-1 have been found in growth hormone disorders of mice and humans. We studied the eventual association between Pit-1 polymorphism using the HinfI enzyme and the milk yield and conformation traits of 89 Italian Holstein-Friesian bulls. A strategy employing polymerase chain reaction was used to amplify a 451-bp fragment from semen DNA. Digestion of polymerase chain reaction products with HinfI revealed two alleles: allele A was not digested (451-bp fragment), and allele B was cut at one restriction site, generating two fragments of 244 and 207 bp. Three patterns were observed; frequencies were 2.2, 31.5, and 66.3% for AA, AB, and BB, respectively. Fixed and mixed linear models were fitted on daughter yield deviations for milk yields and on deregressed proofs for conformation traits. Predictions were weighted using the inverse of the estimated variance of records. The models used contained mean and gene substitution effects for Pit-1 A allele as fixed effects and random sire effect for the mixed model. The A allele was found to be superior for milk and protein yields, inferior for fat percentage, and superior for body depth, angularity, and rear leg set, which is difficult to explain. A canonical transformation revealed that Pit-1 had three actions, one linked to milk yield traits and angularity, a second linked to body depth and rear leg set, and a third linked to lower fat yields and to higher angularity.

Animals↗

PubMed1996

Characterization of growth hormone-binding protein in cattle plasma: prolactin-binding activity and 24-hour profile.

The purpose of this study was to characterize circulating growth hormone-binding proteins (GHBP) and prolactin-binding proteins (PRLBP) in cattle blood plasma. In particular, the 24-hr profile of these molecules was investigated. The preincubation of bull plasma with iodinated bovine growth hormone (bGH) or bovine prolactin (bPRL), followed by gel filtration chromatography (Superdex 200; 1.6 x 60 cm column), resulted in the formation of essentially two complexes. The majority of [125I]bPRL eluted with the first one (M(r) approximately 600 kDa), whereas [125I]bGH mainly appeared in the second one (M(r) approximately 70 kDa). The fractions corresponding to these two peaks were analyzed by western ligand blotting (WLB), under reducing conditions. WLB revealed, respectively, 190-, 56-, 52-, and 28-kDa bands for the first peak and only 52- and 28-kDa bands for the second one. The nature of the 600-kDa peak is at present undetermined, but the 70-kDa one was previously identified as high-affinity GHBP. Displacement studies demonstrated that bGH and bPRL were both able to bind to this GHBP, because the bGH- and bPRL-binding activities of this protein could be saturated by an excess of either of these two hormones. This was indirectly confirmed by the close correlation (r = 0.615; P = 0.0001; n = 155) observed between plasma bGH- and bPRL-binding activities, because this correlation could suggest that both ligands are bound to the same proteins. The temporal concentrations of plasma GHBP were measured in samples collected at 20-min intervals for 24 hr from 8 young bulls. The evaluation of GHBP was realized by WLB, followed by densitometric analysis. Some fluctuations were observed, but these were not correlated with bGH release, even with a +/- 2-hr lag period. In summary, we found that bovine high-affinity GHBP binds not only bGH, but also bPRL. A second type of protein, of higher molecular weight, also binds these two hormones, but further investigations are needed to determine its nature. Finally, GHBP concentrations in cattle blood plasma apparently show fluctuations over a 24-hr period, but no correlation was found between these fluctuations and plasma growth hormone concentrations.

Animals↗

PubMed1996

Effect of propylene glycol supplementation around parturition on milk yield, reproduction performance and some hormonal and metabolic characteristics in dairy cows.

Thirty-nine multiparous Holstein cows were used to measure the effect of propylene glycol treatment around parturition on milk yield, reproductive efficiency and some hormone and metabolite concentrations. Cows were assigned randomly to control (n = 19) or propylene glycol treated (n = 20) groups. Propylene glycol (300 g) was administered directly mixed with the diet from day 10 prior to the expected calving date until parturition (day 0) and orally after dilution in 1 l water on days 3, 6, 9 and 12. Blood samples were collected on days -20, -5, 0, 3, 10, 25 and 50 while milk samples were taken weekly until 13 weeks post partum. Body condition scores, recorded on days -20, 15 and 50, were not affected by propylene glycol administration. Propylene glycol did not significantly affect milk yield or composition but linear somatic cell score measured from the first 13 weeks post partum was reduced by propylene glycol administration (P < 0.01). Moreover, propylene glycol reduced milk urea (-25 mg/l, P < 0.05), especially during the first 9 weeks post partum. Plasma insulin concentrations were similar in both groups during the experiment while insulin-like growth factor I (P < 0.05) and insulin-like growth factor-binding protein 3 (P < 0.001) levels were higher on days 10, 25 and 50 post partum in the propylene glycol group. Propylene glycol administration decreased plasma non-esterified fatty acid concentrations (P < 0.05 to P < 0.01) but increased total cholesterol levels (P < 0.01) after parturition while 3-hydroxybutyrate levels were unaffected by the treatment. Changes in the hormone and metabolic concentrations after propylene glycol administration in the last few days of gestation and the first week of lactation seem to indicate that energy balance in the treated group was probably more positive than in the control group. There was also evidence that propylene glycol administration prevented fatty liver syndrome and hastened the resumption of oestrous cycles (P < 0.001).

Animals↗

PubMed1996

Cellular pathways involved in the ex vivo expression of bovine leukemia virus.

Bovine leukemia virus (BLV) is the etiologic agent of enzootic bovine leukosis. The virus adopts a strategy based on the lack of viral expression in vivo; only very rare BLV-infected B lymphocytes express viral information. When the cells are isolated from animals in persistent lymphocytosis and cultivated ex vivo, a tremendous increase in viral expression occurs. To gain insight into this mechanism, we employed a general approach using chemicals that interfere specifically with cellular pathways involved in signal transduction from the cell membrane to the nucleus. Our data demonstrate that BLV expression is not correlated with the activity of protein kinase A (PKA) and is even inhibited by cyclic AMP (cAMP). The cAMP/PKA pathway is thus apparently not involved in ex vivo viral expression. In contrast, PKC appears to play a key role in this process. Phorbol myristate acetate can directly activate viral expression in B cells (in the absence of T cells). Furthermore, calphostin C, a highly specific inhibitor of PKC, partly decreases ex vivo BLV expression. Our data further demonstrate that calmodulin and calcineurin, a calmodulin-dependent phosphatase, play a key role in the induction of viral expression. The involvement of this calmodulin-dependent pathway could explain the induction of expression that cannot be assigned to PKC. Furthermore, it appears that the activation of viral expression requires a calmodulin but not a PKA-dependent pathway. These data highlight major differences between transient transfection and ex vivo experiments. Finally, despite their homologies, BLV and human T-cell leukemia virus appear to use different signal transduction pathways to induce viral expression.

Animals↗

PubMed1996

Dissociation of increases in plasma insulin-like growth factor I and testosterone during the onset of puberty in bulls.

The present study was conducted to examine the relationship between plasma concentrations of testosterone, insulin-like growth factor I (IGF-I) and IGF-binding proteins (IGFBPs) during puberty, in male calves treated with GnRH or testosterone propionate. Twelve male Holstein calves (10 weeks old) were assigned to the control group (n = 6), the GnRH-treated group (n = 3) or the testosterone-treated group (n = 3). For 8 weeks, the GnRH-treated group received a single i.v. injection of GnRH (0.5 microgram kg-1 body mass) each day while the testosterone-treated group received an i.m. injection of testosterone propionate (0.5 mg kg-1 body mass) twice a day. The calves were studied until they were 200 days old. Hormone treatments were stopped one month after puberty was reached in the control group. Blood samples were collected every 30 min for 8 h every third day. Hormone concentrations were determined by radioimmunoassay. Western ligand blotting and immunoblotting, using monoclonal antibodies against IGFBP-2 and IGFBP-3, were used to characterize the IGF-binding proteins. In the control group, puberty occurred at about 120 days of age and was associated with an increase in concentrations of testosterone, IGF-I and IGFBP-3 and a decrease in concentration of IGFBP-2. In the GnRH-treated group, plasma testosterone remained low until 8 weeks after establishment of puberty in the control group (4 weeks after the end of treatment). In the testosterone-treated group, testosterone was high during the treatment period and then decreased to prepubertal values when treatment was stopped. Testosterone values increased again to reach postpubertal values 5 weeks after the end of hormone treatment. Nevertheless, independent of testosterone status, the profile of IGF-I and the IGFBPs in the GnRH- and testosterone-treated groups were parallel to that reported for the control group with the transition from prepubertal to adult values at about 120 days of age. In conclusion, concentrations of testosterone, IGF-I and IGFBP-3 increase together, but probably independently, during the onset of puberty in male calves.

Animals↗

PubMed1996

Relationships of polymorphisms for growth hormone and growth hormone receptor genes with milk production traits for Italian Holstein-Friesian bulls.

Allelic variation in the structural or regulatory sequences of growth hormone and its receptor genes might directly or indirectly affect milk traits. This possibility prompted us to investigate the eventual relationships of restriction fragment length polymorphisms at the locus of bovine growth hormone (using TagI and MspI restriction enzymes) and its receptor (using TaqI restriction enzyme) to PTA of milk production traits of bulls. Ninety-one Italian Holstein-Friesian bulls were used in this experiment, and data were analyzed with a fixed linear model. The restriction fragment length polymorphisms at the growth hormone locus did not affect the milk traits studied. Six restriction enzyme TaqI bands of 7.1, 6.2, 5.7, 5.4, 4.2, and 3.3 kb with nine patterns were observed after hybridization by a cDNA probe containing the coding sequences for the intracellular C-terminal part of the receptor. The effect of this polymorphism on PTA for milk protein percentage was highly significant and was favorable for the rare (6.6%) 5.7- and 5.4-kb pattern. Our results indicate that further study is needed to explain the DNA polymorphism and to obtain more definite conclusions about effects on milk traits.

Animals↗