Genetic mapping of genes regulating the thymus size in back-cross rats between the laboratory BUF/Mna strain and the MITE strain derived from the wild rat, Rattus norvegicus

The thymoma prone BUF/Mna (B) rat is a useful model for Studying the genes responsible for thymus enlargement during the stage of young growth. Among the strains of rats, B rats have the largest thymuses at al stages of life. A locus, Ten-1 , which contributes to thymus enlargement in back-cross (BC) rats between the B and WKY/NCrj (W) strains, was mapped on chromosome 1. To determine the precise location of the bus, (B×(B×MITE)F1) BC rats were generated by crossing the B strain with the Inbred MITE (M) strain, which was established from captured, Japanese wild rats, and were examined by linkage study using polymerase chain reaction with 67 microsatellite markers. Linkages with thymus enlargements were found In genotypes of seven markers, BSIS, LSN, MYL2, IGF2, PBPC2, D1Mgh11 , and D1Mit6 , by X^2-test and Student's t -test, which confirmed the presence of the genetic locus associated with thymus enlargement, Ten-1 , in this region. Paradoxically, a suppressive locus, Tsu-1 , to thymus enlargement was also found on chromosome 3, showing linkages of phenotype of the small thymus with genotypes of SCN2A, CAT D3Mit16 , and D3Mit13 . By analyses of mapmaker/exp and mapmaker/qtl, Ten-1 was mapped at 4.6 cM proximal from IGF2 locus on chromosome 1 and Tsu-1 at 4.0 cM proximal from CAT locus on chromosome 3, respectively.     

Fine mapping of thymus enlargement gene 1 (Ten1) in BUF/Mna rats

Two polymeric autosomal loci, Ten1 and Ten2, regulate thymus enlargement in BUF/Mna (B) rats. Previously, we mapped Ten1 on chromosome (Chr) 1 to a 20 cM region between Myl2 and D1Mgh11, and Ten2 on Chr 13. To further characterize the precise position of Ten1, 34 and 37 microsatellite markers, that have a polymorphism between the B and WYK (W) and between the B and MITE (M) strains, were used for linkage analysis of thymus enlargement in 105 (WBF1 x B) blackcross (BC) and 78 (B x BMF1) BC rats, respectively. Our data showed that the D1Rat168, D1Rat112, D1Rat323, D1Got186, D1Got187 and D1Got188 markers each gave a peak logarithm of odds (LOD) score of 10.68 for linkage to the thymus ratio in (WBF1 x B) BC rats, and that the D1Rat168, D1Rat197, D1Got184, D1Got186 and D1Got188 markers each gave a peak LOD score of 7.82 in (B x BMF1) BC rats. The two LOD score peaks are coincident in the position of the rat genetic map. All of the markers mentioned above are located in the region between Igf2 and D1Mgh11, in which synteny is conserved with human 11q15.5 and the distal end of mouse Chr 7 or with human 11q13 and the proximal end of mouse Chr 19. Genes existing in these regions are discussed as candidate genes for Ten1.     

Molecular diversity and phylogenetic analysis of mariner-like transposons in the genome of the silkworm Bombyx mori

Genome-wide screening of mariner-like elements (MLEs) in the silkworm Bombyx mori has revealed the presence of five different types of MLEs (Bmmar1, Bmmar2, Bmmar3, Bmmar4 and Bmmar5). We isolated and characterized sixty copies of the MLEs representing the five Bmmar types. Their nucleotide sequences, nucleotide compositions, deduced transposase sequences, codon preferences, and the copy numbers showed extensive variations. Phylogenetic analysis of the sequences revealed that Bmmar1, Bmmar2, and Bmmar3 have been in the B. mori genome for a long time, while Bmmar4 is probably a recent invader of the genome. Because of the long-term association of Bmmar1 and Bmmar2 with the genome, highly mutated miniature Bmmar1 and Bmmar2 are widespread in the genome, and the footprints of these elements are also present in different silkworm genes. However, miniature copies of Bmmar4 were not detected. This recently acquired element has very few mutations. None of the characterized copies had functional transposase open reading frames. They essentially exist as fossils in the genome.     

HOUSE DUST MITE ALLERGEN （Derp1 AND Blot5） LEVELS IN ASTHMATICS＇ HOME IN HONGKONG

Objective To measure Derpl and Blot5 allergen levels in asthmatics' homes in Hongkong.Methods Seventy houses were enrolled for a mite indoor environment study. Dust samples were obtained from two sites of each patients' house: bed and floor. Derpl and Blot5 levels were quantified by a two-site monoclonal antibody-based ELISA technique.Results The levels of Derpl allergens found in bed (geometric mean (GM) 3.43 μg/g of dust; 95%CI, 1.89-4.96 μg/g)and on the floor (GM 1.12 μg/g of dust; 95%CI, 0.71-1.53 μg/g) indicated significant differences (P=0.005). However, the levels of Blot5 allergens found in bed (GM 19.00 μg/g of dust; 95%CI, 0.89-38.90 μg/g) and on the floor (GM 6.14 μg/g of dust; 95%CI, 0.40-11.90 μg/g) showed no statistically significant difference. In addition, in regards to the exposure index for Derpl and Blot5 allergens found in bed and on the floor, 17.6% in bed and 8.6% on the floor had levels of Blot5 ≥ 10 μg/g of dust, higher than those obtained for Derp1 (7.2% and 0% in bed and on the floor respectively, P＜ 0.05); higher percentages in bed and on the floor (25.0% and 35.7%) were observed for levels of Blot5 =0 μg/g of dust as compared with Derpl in bed and on the floor (4.3% and 14.5% respectively, P＜ 0.05).Conclusions Derpl and Blot5 are the major allergens found in this regional study, Blot5 is a more potent allergen in Hongkong, probably reflecting the high level of exposure to Blomia tropicalis (Bt). Bt and Dermatophagoides pteronyssinus (Dp) allergens should be included for precise diagnosis and effective immuno-therapeutic treatment of mite allergy in Hongkong.