Short communication: Identification of variation in the ovine prolactin gene of Chios sheep with a cost-effective sequence-based typing assay.

The present study identified single nucleotide polymorphisms (SNP) in the coding and untranslated regions of the ovine prolactin gene of Chios sheep. By developing a cost-effective direct sequence-based typing assay, around 600 bp of reliable sequencing data and clear identification of heterozygous positions was achieved. Five SNP were found, located in exons 2 (KC764410:g.567G>A, g.625C>T, g.683C>A) and 3 (KC764410:g.2015C>A, g.2101G>A), whereas the remaining exons were monomorphic. The identified SNP were synonymous, with the exception of the g.567G>A SNP, which results in an Arg to His amino acid change. As the sequencing cost of the sequence-based typing assay was 20 orders of magnitude lower compared with a standard Sanger method, the assay was also used as a genotyping tool. The identified polymorphism was genotyped for 247 ewes and was subsequently used in mixed model association analyses of milk yield, milk fat content, and litter size at birth. The association analysis revealed a significant dominance effect of 0.17 ± 0.07 of the g.2015C>A SNP on milk fat percentage, whereas a dominance effect of -21.33 ± 10.51 of the same SNP on total lactation milk yield was also estimated. The g.2015C>A SNP explained 2.47 and 3.68% of the total phenotypic variance of milk yield and milk fat percentage, respectively, whereas the corresponding values for the animal variance were 7.14 and 11.75%. A suggestive association of the nonsynonymous g.567G>A SNP with litter size at birth was also detected.

Partial suckling of lambs reduced the linoleic and conjugated linoleic acid contents of marketable milk in Chios ewes.

The objective of this work was to investigate the effect of weaning systems applied in a commercial dairy sheep farm on the fatty acid (FA) composition of marketable milk produced. Forty second parity, purebred Chios ewes were allocated to the following weaning treatments: (a) ewes were weaned from their lambs at 48 h after birth and machine milked twice daily [no lambs (NL) group, n=20]; or, (b) starting 48 h postpartum, ewes were separated from their lambs for 12h during the evening, machine milked once daily the following morning, and lambs were allowed to suckle for 12 h during the day for the first 5 wk of lactation [partial suckling (PS) group, n=20]. After weaning of the PS lambs at wk 6 of age, all ewes were machine milked twice daily. Commercial milk yield and milk composition was recorded weekly (fat, protein, FA content) or fortnightly (somatic cell counts) throughout the first 10 wk of lactation. The PS ewes compared with NL group produced commercial milk lower in milk yield, milk fat, and somatic cell counts, but not in protein content during the first 5-wk period. Such differences were not observed after weaning of the PS lambs. The FA profile of commercial milk was also affected by partial suckling during the preweaning period. Total polyunsaturated FA were higher in NL compared with PS ewe milk at wk 1, 2, 4, and 5 (on average, 21% higher), whereas no differences were detected between NL and PS ewe milk from wk 6 to 10 of lactation. From the polyunsaturated FA, linoleic acid (C18:2 cis-9,cis-12) and conjugated linoleic acid (C18:2 cis-9,trans-11; rumenic acid) were particularly affected, showing on average a reduction of 18 and 38%, respectively. From the monounsaturated FA, vaccenic acid (C18:1 trans-11) was affected during wk 1 and 2 of the treatment period, with the PS ewe milk having reduced content compared with the NL milk. Other unsaturated FA, such as oleic acid and α-linolenic acid, or saturated FA were not found to be affected by the weaning treatment. The results indicate that partial suckling of lambs during the first 5 wk of lactation adversely affected both the total fat content of milk obtained by machine milking of their dams and the unsaturation content of the milk fat. Particularly affected were the linoleic acid and cis-9,trans-11 conjugated linoleic acid content of ewe milk.

Assessment of inbreeding resulting from selection for scrapie resistance: a model for rare sheep breeds.

Inbreeding in a small population of Chios sheep undergoing intense selection for the PrP gene was assessed 10 years after the beginning of a scrapie resistance selection programme. Inbreeding in this stock, already under selection for production traits, was analysed by using pedigree records containing 10,492 animals from 1968 to 2008, and also by genotyping 192 individuals with a panel of 15 microsatellites. Genetic markers indicated a loss of heterozygosity (FIS over all loci was 0.059) and allelic diversity (mean effective number of alleles was 3.075±0.275). The annual rate of inbreeding increased significantly after the start of the scrapie resistance programme, ΔF=0.005 compared with ΔF=0.001 before 1999, and was subjected to several genetic bottlenecks, mainly due to the low initial frequency of resistant animals. However, the mean individual inbreeding coefficient estimated from the pedigree - in this closed stock resembling the case of a rare breed - stood at the level of 4.5 per cent, five generations after the implementation of selection for the PrP gene. The inbreeding coefficient estimated by genetic markers was 4.37 per cent, implying that such a marker panel could be a useful and cost-effective tool for estimating inbreeding in unrecorded populations.

A single nucleotide polymorphism in the acetyl-coenzyme A acyltransferase 2 (ACAA2) gene is associated with milk yield in Chios sheep.

The objective of this work was to identify single nucleotide polymorphisms (SNP) in the ovine acetyl-coenzyme A acyltransferase 2 (ACAA2) gene and investigate their association with milk production traits. Molecular characterization was accomplished by sequencing the entire coding region and the 3' and 5' untranslated regions (UTR) of the ACAA2 gene from individuals of the Chios sheep bred in Cyprus. All exons appeared to be monomorphic except for the last exon, for which a single SNP located in the 3' UTR of the gene (HM537015:g.2982T>C) was detected. Mixed model association analysis, using SNP data from 318 animals from 104 paternal half-sib families and first-lactation phenotype and pedigree information on 2,405 ewes revealed that this SNP was significantly associated with milk yield. The significance of the SNP effect persisted when milk yield information up to the third lactation was analyzed. Both alleles at the locus segregated at similar frequencies. The T allele was associated with increased milk yield and exhibited partial dominant action. Animals with the g.2982TT or g.2982CT genotype had significantly higher milk yield than those with the g.2982CC genotype, with the g.2982T allele having an additive effect of 13.4 (± 4.7) kg and a dominance effect of 7.9 (± 6.1) kg. Based on estimated allelic effects and sample allele frequencies, the g.2982T>C SNP explained 10% of the additive genetic variance for milk yield. A putative mode of action through nutrient metabolism is discussed.

Technical note: A simplified PCR-based assay for the characterization of two prolactin variants that affect milk traits in sheep breeds.

In the present study, a rapid and cost-effective PCR-based assay was developed for the genetic identification of 2 different variants within intron 2 of the prolactin gene. This polymorphism has previously been associated with milk traits in some ovine breeds and was recently proposed as a potential marker for future breeding schemes in dairy sheep. Until now, 2 alleles (A and B) have been identified by PCR-RFLP that included HaeIII digestion of a 2.5-kb PCR fragment. By partial sequencing of the prolactin gene intron 2, it was found that the B variant results from a 23-bp deletion of the A variant of the prolactin gene and not from an extra HaeIII digestion site, as had been reported. This finding assisted the design of new primers for analysis of prolactin intron 2 variants based on the size of an easily amplified short PCR product, thereby avoiding the need and cost for additional digestions. The method was validated by genotyping 80 animals from 2 breeds and showed 100% sensitivity and specificity compared with the PCR-RFLP assay. The established simplified PCR assay was then successfully used to genotype 356 Chios sheep.

Engineering EGFP reporter constructs into a 200 kb human beta-globin BAC clone using GET Recombination.

GET Recombination, a simple inducible homologous recombination system for Escherichia coli, was used to target insertion of an EGFP cassette between the start and termination codons of the beta-globin gene in a 200 kb BAC clone. The high degree of homology between the promoter regions of the beta- and delta-globin genes also allowed the simultaneous generation of a delta-globin reporter construct with the deletion of 8.8 kb of intervening sequences. Both constructs expressed EGFP after transient transfection of MEL cells. Similarly, targeting of the EGFP cassette between the promoter regions of the gamma-globin genes and the termination codon of the beta-globin gene enabled the generation of reporter constructs for both (A)gamma- and (G)gamma-globin genes, involving specific deletions of 24 and 29 kb of genomic sequence, respectively. Finally the EGFP cassette was also inserted between the epsilon- and beta-globin genes, with the simultaneous deletion of 44 kb of intervening sequence. The modified constructs were generated at high efficiency, illustrating the usefulness of GET Recombination to generate large deletions of specific sequences in BACs for functional studies. The establishment of stable erythropoietic cell lines with these globin constructs will facilitate the search for therapeutic agents that modify the expression of the individual globin genes in a physiologically relevant manner.

A low-Km 5'-nucleotidase from rat brain cytosolic fraction: purification, kinetic properties, and description of regulation by a novel factor that increases sensitivity to inhibition by ATP and ADP.

A readily soluble 5'-nucleotidase was purified 1,800-fold from rat brain 105,000-g supernatant. The enzyme showed similarity to the 5'-nucleotidase ectoenzyme of plasma membranes. It exhibited a low Km for AMP, which was preferred over IMP as substrate. It was inhibited by free ATP and ADP and by alpha,beta-methylene ADP. The enzyme appeared to be a glycoprotein on the basis of its interaction with concanavalin A. It contained a phosphatidylinositol moiety because treatment with phosphatidylinositol-specific phospholipase C increased its hydrophilicity. A single subunit of Mr = 54,300 +/- 800 was observed, which is appreciably smaller than published values for the 5'-nucleotidase ectoenzyme or for other low- Km "soluble" 5'-nucleotidases. The soluble 5'-nucleotidase showed an elution profile on AMP-Sepharose affinity chromatography or on Mono Q ion-exchange chromatography different from that of the brain ectoenzyme. Forty-two percent of the soluble 5'-nucleotidase in brain 105,000-g supernatant did not bind to a Mono Q ion-exchange column because of its interaction with a soluble factor. This factor could be removed by chromatography on concanavalin A-Sepharose. The factor had the novel property of increasing the sensitivity of the purified soluble 5'-nucleotidase toward the inhibitor ATP by 20-fold. This factor was also able to increase the inhibition of brain 5'-nucleotidase ectoenzyme by ATP.

Neonatal carnitine palmitoyltransferase-2 deficiency: a case presenting with myopathy.

Mitochondria were isolated from liver, heart and skeletal muscle of a 34-day-old female infant who died from a myopathic illness. Muscle biopsy showed lipid accumulation and no obvious pathology in any other organ. Enzymatic analysis of skeletal muscle extracts revealed normal activities of the markers pyruvate dehydrogenase and citrate synthase. Malonyl-CoA-sensitive carnitine palmitoyltransferase (CPT1) was detected but malonyl-CoA-insensitive carnitine palmitoyltransferase (CPT2) appeared to be absent. Quantitative immunoblotting revealed the presence of a normal abundance of CPT2 protein in the patient's muscle. It is concluded that enzymically inactive CPT2 protein was present.

Treatment with triiodothyronine decreases the abundance of the alpha-subunits of Gi1 and Gi2 in the cerebral cortex.

Treatment of rats for 3 days with T3 halved the abundance of the alpha-subunits of Gi1 and Gi2 in synaptosomal membranes isolated from the cerebral cortex. It is suggested that these changes could contribute to behavioural abnormalities in hyperthyroidism. Similar T3 treatment did not alter abundance of Gi1 alpha or Gi2 alpha in the medulla oblongata nor did it alter abundance of G(o) alpha-subunits in three tested brain regions.

Abundance of the alpha-subunits of Gi1, Gi2 and Go in synaptosomal membranes from several regions of the rat brain is increased in hypothyroidism.

1. Rats (4 weeks old) were made hypothyroid by treatment with propylthiouracil together with a low-iodine diet for a further period of 4 weeks. Synaptosomal membranes were obtained from six anatomical regions of the brain. 2. The abundances in these membranes of the G-protein alpha-subunits Gi1 alpha, Gi2 alpha and Go alpha were measured by quantitative immunoblotting. 3. Hypothyroidism significantly increased the abundances of all three G-protein subunits in membranes from the cerebral cortex and the striatum. In the medulla oblongata and the hippocampus the abundances of Gi2 alpha and Go alpha were increased significantly. By contrast, in the cerebellum only Go alpha was increased, and in the hypothalamus only Gi2 alpha was increased. 4. It is suggested that this up-regulation of G-protein abundances may modify signalling pathways and may contribute to the functional changes that are observed in the central nervous system in hypothyroidism.

Soluble 5'-nucleotidase activities in rat brain.

5'-Nucleotidase activity was assayed in 105,000-g supernatants from rat brain by following conversion of [3H]AMP into adenosine. The effect of ATP on this process was complex and suggested the presence of at least two soluble 5'-nucleotidase activities: one inhibited by ATP and another activated by ATP. The relative proportions of these activities differed considerably among brain regions. Activity changes induced by hypothyroidism also suggested that these activities may be regulated independently. These findings may have consequences for the regional regulation of adenosine formation in the brain.

Diabetes decreases sensitivity of adipocyte lipolysis to inhibition by Gi-linked receptor agonists.

(1) Streptozotocin-diabetes decreased the responsiveness of noradrenaline- or forskolin-stimulated lipolysis to inhibition by phenylisopropyladenosine (PIA), prostaglandin E1 (PGE1) and nicotinate in rat adipocytes. (2) Diabetes had no effect on high affinity binding of [3H]PIA to adipocyte plasma membranes. (3) Plasma membranes from diabetic animals had increased abundance of alpha-subunits of Gi1 and Gi2. The effect of pertussis toxin in overcoming inhibition of lipolysis by PIA was delayed in adipocytes from diabetic rats. (4) Diabetes decreased the GTP-dependent right-wards shift in the dose-curve for displacement of the antagonist [3H]DPCPX by PIA in adipocyte plasma membranes. (5) It is concluded that, despite increased abundance of Gi in diabetic adipocytes, less of this is functional. This may contribute to reduced sensitivity to PIA, PGE1 and nicotinate and explains some of the loss of control of lipolysis in insulin-dependent diabetes.