Chromosomal distribution of major rDNA and genome size variation in Belostoma angustum Lauck, B. nessimiani Ribeiro & Alecrim, and B. sanctulum Montandon (Insecta, Heteroptera, Belostomatidae)

Known as "electric-light bugs", belostomatids potentially act as agents of biological control. The Belostoma genus has holokinetic chromosomes, interspecific variation in diploid number, sex chromosome system and DNA content. Thus, the chromosomal complement, the accumulation of constitutive heterochromatin and the distribution of rDNA clusters by fluorescence in situ hybridization (FISH) in Belostoma angustum (BAN), Belostoma sanctulum (BSA), and Belostoma nessimiani (BNE) were evaluated. In addition, a comparative analysis of the DNA content of these species and B. estevezae (BES) was performed. BES has the highest Belostoma DNA content, while BSA has the lowest. BAN showed 2n = 29 + X₁X₂Y, while BSA and BNE had 2n = 14 + XY. BSA showed 18S rDNA markings on sex chromosomes, while BNE and BAN did on autosomes. The difference between BSA and BNE occurs because of the possible movement of the rDNA cluster in BNE. We suggest the occurrence of fusion in the autosomes of BSA and BNE, and fragmentation in the sex chromosomes in BAN. Also, the genome size of 1-2 pg represents a haploid DNA content of a common ancestor, from which the genomes of BES and BAN had evolved by gene duplication and heterochromatinization events.

The chemokine receptor CCR5 genetic polymorphism and expression in rheumatoid arthritis patients

OBJECTIVES

To identify the genetic polymorphism of the chemokine receptor CCR5 (the Delta32 allelic variant) in patients with rheumatoid arthritis (RA) and compare the findings with healthy controls. To compare the CCR5 phenotypic expression in T cells and monocytes isolated from the peripheral blood and synovial fluid in a subgroup of RA patients.

METHODS

CCR5 genes of 92 RA patients and 160 healthy controls were genotyped using specific primers flanking the region of deletion. The ethnic distribution was similar between the groups. Flow cytometric analysis was used for immunophenotyping the T cells and monocytes isolated from the peripheral blood and synovial fluid of eight RA patients. The isolated cells were triple stained with CD4 or CD8, CD25 and CCR5 monoclonal antibodies.

RESULTS

There was no difference in the CCR5Delta32 genotypic frequency between the RA patients and the control group (0.055 and 0.063, respectively, p = 0.989). No homozygote for the CCR5Delta32 allele was seen in either group. Five heterozygotes were identified in the RA patient group, whose disease was shown to be aggressive. A significant enrichment of activated CCR5+ monocytes was seen in the synovial fluid of the RA patients subjected to arthrocentesis, who were all homozygotes for the CCR5 wild-type genotype.

CONCLUSION

A protective role for the CCR5 allelic variant in RA development was not observed. Disease severity in the heterozygotes suggests that other proinflammatory mechanisms might overcome this mutation in vivo. The activated CCR5+ monocyte enrichment in the rheumatoid synovial fluid might indicate that this cell population has an important role in the pathogenesis of the disease.