Sin H Phua

Facial eczema (FE) is a hepatogenous mycotoxicosis in sheep caused by the fungal toxin sporidesmin. Resistance to FE is a multigenic trait. To identify QTL associated with this trait, a scan of ovine chromosomes was implemented. In addition, ABCG2 was investigated as a possible positional candidate gene because of its sequence homology to the yeast PDR5 protein and its functional role as a xenobiotic transporter. The sequence of ovine ABCG2 cDNA was obtained from liver mRNA by RT-PCR and ...

AIM: To use an established high through-put genotyping procedure to gain an estimate of the frequency of alleles of the prion protein (PrP) gene in some common sheep breeds in New Zealand.

METHODS: Using a genotyping procedure based on matrix-assisted laser desorption ionisation-time of flight (MALDI-TOF), DNA samples from 3,024 sheep from New Zealand, including breeds such as Romney, Texel, Coopworth, Merino and mixed breed, were isolated, genotyped and the results analysed.

RESULTS: ...

Facial eczema (FE) is a hepatogenous photosensitization disease of ruminant animals, particularly in sheep which vary widely in their susceptibility to the disease. The liver damage is caused by the mycotoxin, sporidesmin. There is evidence that the toxicity of sporidesmin is due to its ability to generate 'active oxygen' species. We evaluated the catalase gene, which encodes an enzyme with antioxidant functions, as a candidate for determining the susceptibility of sheep to the disease. ...

Facial eczema (FE) is a secondary photosensitization disease arising from liver cirrhosis caused by the mycotoxin sporidesmin. The disease affects sheep, cattle, deer and goats, and costs the New Zealand sheep industry alone an estimated NZ$63M annually. A long-term sustainable solution to this century-old FE problem is to breed for disease-resistant animals by marker-assisted selection. As a step towards finding a diagnostic DNA test for FE sensitivity, we have conducted a genome-scan ...

The DNA sequences of the control region of the mitochondrial genome of fifty unrelated sheep were determined in order to ascertain the extent and distribution of its variability. A consensus sequence was derived, and 1081 differences from it were observed amongst the fifty animals. Some constant groups of differences were observed that were held in common by a number of animals, which thus fell into two main groups, although neither group was typical of any of the breeds sampled. The ...

Sporidesmin is an epidithiodioxopiperazine mycotoxin secreted by the saprophytic fungus Pithomyces chartarum. Ingestion of sporidesmin by ruminants grazing on the saprophyte infested pasture causes severe liver and bile duct damage leading to secondary photosensitisation. Zinc supplementation is used as an effective prophylaxis against sporidesmin toxicity in ruminants, however, the mechanism by which zinc protects is unknown. This study used the human hepatoma cell line, HepG2, as a ...

Romney sheep have been evaluated for resistance to facial eczema (FE) using a process which involves challenge with the FE toxin, sporidesmin, and they have been bred in selection lines for increased resistance (R) or susceptibility (S) to FE. There is evidence that sporidesmin exerts its toxic effects by generating reactive oxygen species, and protection can be afforded by a number of antioxidants and antioxidant enzymes. Our objective was to summarise three separate experiments to ...

Facial eczema (FE) is a costly problem to New Zealand pastoral agriculture, and has a detrimental impact on animal wellbeing. Incidence and severity of the disease can be reduced by grazing management and zinc prophylaxis. An additional strategy is to breed animals that are genetically resistant to intoxication with sporidesmin, the causative mycotoxin. This review summarises research findings on the inheritance of resistance of animals to FE, including evidence of among- and ...

Mitochondrial DNA (mtDNA) is a widely employed molecular tool in phylogeography, in the inference of human evolutionary history, in dating the domestication of livestock and in forensic science. In humans and other vertebrates the popularity of mtDNA can be partially attributed to an assumption of strict maternal inheritance, such that there is no recombination between mitochondrial lineages. The recent demonstration that linkage disequilibrium (LD) declines as a function of distance ...

A DNA repeat element, revealed initially by digestion of horse DNA with TaqI, was cloned and characterized by Southern and in situ hybridization studies and nucleotide sequencing. The clone, e4/1, consisted of 32 tandem reiteration of a unit repeat of 21-22 bp, and produced multilocus DNA fingerprinting profiles that were useful for parentage analysis in horses. The tandem repeat element was shown by in situ hybridization to be localized in the centromeres of the acrocentric but not ...

Long term divergent selection lines for resistance and susceptibility to two diseases of sheep were utilized to look for disease resistance QTL. The diseases were facial eczema, which is caused by a saprophytic fungus of pasture which produces toxic spores, and gastro‐intestinal parasitic nematodes. Sires derived from reciprocal crosses of the lines were mated with unrelated dams to generate large half‐sib pedigrees, which were then measured for traits known to be related to the disease ...

Facial eczema (FE) is a hepato-mycotoxicosis found mainly in New Zealand sheep and cattle. When genetics was found to be a factor in FE susceptibility, resistant and susceptible selection lines of Romney sheep were established to enable further investigations of this disease trait. Using the Illumina OvineSNP50 BeadChip, we conducted a selection-sweep experiment on these FE genetic lines. Two analytical methods were used to detect selection signals, namely the Peddrift test (Dodds & ...

Pithomycotoxicosis, more commonly known as facial eczema (FE), is a liver disease that occurs predominantly in New Zealand because of its toxigenic Pithomyces chartarum strains. The first reported case was in sheep in 1887. Since the 1930s, a number of studies have been conducted in an attempt to mitigate the problems FE has on the sheep and dairy industries. The research in these studies included work on fungicide and biological control of the saprophytic fungus, use of different ...

The first ruminant multiple drug resistance gene (MDR1) has been cloned and sequenced from sheep. Sequence data revealed the sheep MDR1 gene to have high sequence and structural similarity to other characterized MDR proteins from humans and rodents. A restriction fragment length polymorphism was discovered using the EcoRI enzyme and used to map the MDR1 gene to sheep chromosome 4. Physical mapping using fluorescent in situ hybridisation confirmed this map placement and assigned the MDR1 ...