Fine mapping of the MHC Class III region demonstrates association of AIF1 and rheumatoid arthritis.

OBJECTIVES: The heritability of RA has been estimated to be approximately 55%, of which the MHC contributes about one-third. HLA-DRB1 alleles are strongly associated with RA, but it is likely that significant non-DRB1 MHC genetic susceptibility factors are involved. Previously, we identified two three-marker haplotypes in a 106-kb region in the MHC class III region immediately centromeric to TNF, which are strongly associated with RA on HLA-DRB1*0404 haplotypes. In the present study, we aimed to refine these associations further using a combination of genotyping and gene expression studies. METHODS: Thirty-nine nucleotide polymorphisms (SNPs) were genotyped in 95 DRB1*0404 carrying unrelated RA cases, 125 DRB1*0404-carrying healthy controls and 87 parent-case trio RA families in which the affected child carried HLA-DRB1*04. Quantitative RT-PCR was used to assess the expression of the positional candidate MHC class III genes APOM, BAT2, BAT3, BAT4, BAT5, AIF1, C6orf47, CSNK2beta and LY6G5C, and the housekeeper genes, hypoxanthine-guanine phosphoribosyltransferase (HPRT) and beta(2)-microglobulin (B2M) in 31 RA cases and 21 ethnically, age- and sex-matched healthy controls. Synovial membrane specimens from RA, PsA and OA cases were stained by an indirect immunoperoxidase technique using a mouse-anti-human AIF1 monoclonal antibody. RESULTS: Association was observed between RA and single markers or two marker haplotypes involving AIF1, BAT3 and CSNK. AIF1 was also significantly overexpressed in RA mononuclear cells (1.5- to 1.9-fold difference, P = 0.02 vs HPRT, P = 0.002 vs B2M). AIF1 protein was clearly expressed by synovial macrophages in all the inflammatory synovial samples in contrast to the non-inflammatory OA samples. CONCLUSIONS: The results of the genotyping and expression studies presented here suggest a role for AIF1 in both the aetiology and pathogenesis of RA.

The efficacy of a vitamin D(3) metabolite for improving the myofibrillar tenderness of meat from Bos indicus cattle.

The influence of a once only administration of a metabolite of vitamin D(3) (HY·D(®)-25-hydroxy vitamin D(3)) on myofibrillar meat tenderness in Australian Brahman cattle was studied. Ninety-six Brahman steers of three phenotypes (Indo-Brazil, US and US/European) and with two previous hormonal growth promotant (HGP) histories (implanted or not implanted with Compudose(®)) were fed a standard feedlot ration for 70d. Treatment groups of 24 steers were offered daily 10g/head HY·D(®) (125mg 25-hydroxyvitamin D(3)) for 6, 4, or 2d before slaughter. One other group of 24 steers was given the basal diet without HY·D(®). Feed lot performance, blood and muscle samples and carcass quality data were collected at slaughter. Calcium, magnesium, potassium, sodium, iron and Vitamin D(3) metabolites were measured in plasma and longissimus dorsi muscle. Warner-Bratzler (WB) shear force (peak force, initial yield) and other objective meat quality measurements were made on the longissimus dorsi muscle of each steer after ageing for 1, 7 and 14d post-mortem at 0-2°C. There were no significant effects of HY·D(®) supplements on average daily gain (ADG, 1.28-1.45kg/d) over the experimental period. HY·D(®) supplements given 6d prior to slaughter resulted in significantly higher (P<0.05) initial yield values compared to supplements given 2d prior to slaughter. Supplementation had no significant effect on meat colour, ultimate pH, sarcomere length, cooking loss, instron compression or peak force. There was a significant treatment (HY·D(®)) by phenotype/HGP interaction for peak force (P=0.028), in which Indo-Brazil steers without previous HGP treatment responded positively (increased tenderness) to HY·D(®) supplements at 2d when compared with Indo-Brazil steers previously given HGP. There were no significant effects of treatment on other phenotypes. HY·D(®) supplements did not affect muscle or plasma concentrations of calcium, potassium or sodium, but did significantly decrease plasma magnesium and iron concentrations when given 2d before slaughter. There were no detectable amounts of 25-hydroxyvitamin D(3) in the blood or muscle of any cattle at slaughter.