Insulin-like growth factor-I attenuates the inhibitory effect of type I collagen through beta1 integrin receptor

Extracellular matrix and growth factors are the crucial factors that regulate healing and regenerating processes in human periodontal ligament cells. The purpose of this study was to examine the effects of type I collagen and insulin-like growth factor-I (IGF-I) on osteopontin (OPN) expression. The data showed that OPN expression was significantly decreased when cells were cultured on collagen-coated plates. Addition of IGF-I obviously induced OPN expression only in a collagen-coated condition, suggesting an attenuating effect of IGF-I on the decrease of OPN expression. Cells treated with a combination of inhibitory antibody to beta1 integrin and IGF-I showed the same level of OPN expression as those treated with either inhibitory antibody to beta1 integrin or IGF-I alone. These results indicate that IGF-I counteracts with the inhibitory signal from type I collagen through beta1 integrin receptor.     

Cytoplasmic sequestration of cyclin D1 associated with cell cycle withdrawal of neuroblastoma cells

The regulation of D-type cyclin-dependent kinase activity is critical for neuronal differentiation and apoptosis. We recently showed that cyclin D1 is sequestered in the cytoplasm and that its nuclear localization induces apoptosis in postmitotic primary neurons. Here, we further investigated the role of the subcellular localization of cyclin D1 in cell cycle withdrawal during the differentiation of N1E-115 neuroblastoma cells. We show that cyclin D1 became predominantly cytoplasmic after differentiation. Targeting cyclin D1 expression to the nucleus induced phosphorylation of Rb and cdk2 kinase activity. Furthermore, cyclin D1 nuclear localization promoted differentiated N1E-115 cells to reenter the cell cycle, a process that was inhibited by p16(INK4a), a specific inhibitor of D-type cyclin activity. These results indicate that cytoplasmic sequestration of cyclin D1 plays a role in neuronal cell cycle withdrawal, and suggests that the abrogation of machinery involved in monitoring aberrant nuclear cyclin D1 activity contributes to neuronal tumorigenesis.     

Population structure,population history and DNA barcoding of fruit fly Bactrocera latifrons (Hendel) (Diptera: Tephritidae)

The fruit fly Bactrocera latifrons (Hendel) is an important pest of commercially significant plants such as chili, tomato and eggplant. The species is native to South and Southeast Asia, but has now invaded Japan, Hawaii and Africa. In this study, mitochondrial DNA sequences were used to infer genetic structure and demographic history of B. latifrons. The efficiency of DNA barcodes for identification of B. latifrons was also tested. Ninety‐three specimens infesting four host‐plant species were obtained from 11 sampling locations in Thailand. The mitochondrial haplotype network revealed no major divergent lineage, which was consistent with a phylogenetic analysis that found strong support for the monophyly of B. latifrons. Population pairwise F_ST revealed that most (65%) comparisons were not significantly different, suggesting a high rate of gene flow. Analysis of molecular variance (amova ) found no significant genetic differentiation among populations from different host‐plant species. Sharing of several haplotypes among flies from different host‐plants indicates that the flies were moved freely across the plant species. Demographic history analysis revealed that the population has undergone recent expansion dating back to the end of the last glaciation. Thus, the results indicate that both ongoing and historical factors have played important roles in determining the genetic structure and diversity of B. latifrons. DNA barcoding analysis revealed that B. latifrons specimens were clearly differentiated from other species with 100% correct identification. Therefore, cytochrome oxidase I (COI) barcoding sequences could be effectively used to identify this important pest species, which could encourage monitoring and control efforts for this species.     

Phylogenetic analysis based on multiple gene sequences revealing cryptic biodiversity in Simulium multistriatum group (Diptera: Simuliidae) in Thailand

Phylogenetic relationships among four species of the Simulium multistriatum group (Diptera: Simuliidae) in Thailand were examined based on two mitochondrial genes (COI, COII) and one nuclear gene (18S/ITS1). Simulium takense was found to be genetically divergent (>20.3% for COI) from the other species, consistent with their distinctive morphology. Simulium chainarongi and S. chaliowae were monophyletic but were included in paraphyletic S. fenestratum. Simulium fenestratum was divided into three distinct lineages with high levels of genetic divergence. This suggests that S. fenestratum is a species complex. Neither morphological nor cytological examinations revealed evidence of sibling species. The clades derived from phylogenetic analyses were found to be correlated with the ecological conditions of larval habitat. Therefore, ecological adaptation may have played a role in black fly diversification and evolution. These results suggest the use of integrated, multidisciplinary approaches for fully understanding black fly biodiversity and systematics.     

The role of genetic diversity in nest cooling in a wild honey bee, Apis florea

Simulation studies of the task threshold model for task allocation in social insect colonies suggest that nest temperature homeostasis is enhanced if workers have slightly different thresholds for engaging in tasks related to nest thermoregulation. Genetic variance in task thresholds is one way a distribution of task thresholds can be generated. Apis mellifera colonies with large genetic diversity are able to maintain more stable brood nest temperatures than colonies that are genetically uniform. If this phenomenon is generalizable to other species, we would predict that patrilines should vary in the threshold in which they engage in thermoregulatory tasks. We exposed A. florea colonies to different temperatures experimentally, and retrieved fanning workers at these different temperatures. In many cases we found statistically significant differences in the proportion of fanning workers of different patrilines at different experimental temperatures. This suggests that genetically different workers have different thresholds for performing the thermoregulatory task of fanning. We suggest, therefore, that genetically based variance in task threshold is a widespread phenomenon in the genus Apis.     

Phylogeography of Simulium siamense Takaoka and Suzuki complex (Diptera: Simuliidae) in Thailand

The phylogeography of Simulium siamense complex was inferred from mitochondrial DNA sequences. A 586‐bp fragment of the cytochrome oxidase I was sequenced for 92 individuals from 13 populations throughout Thailand, representing five cytoforms (A, B, C, F and G). The cytoforms are not genetically different at the molecular level except for cytoform B, which is genetically distinct from the others. This might indicate that cytoform B is a distinct species. Further morphological and molecular work using other genes is needed to clarify this. Our results also argue for the need of integrated approach, both cytological and molecular studies to understanding biodiversity of black flies. The star‐like shape of the mtDNA genealogy is consistent with the sudden population expansion of the mismatch distribution analysis and large negative values of Fu's F_s and Tajima's D‐tests, indicating a population demographic expansion. The expansion time is estimated to be in the late Pleistocene (about 120 000 years ago). Therefore, the overall low level of genetic structure could be due to sharing a recent history. The ancestral haplotype was found in the mountainous area in northeastern Thailand, suggesting that this area could have been the refugium of the species complex during the Pleistocene glaciations. Our results are consistent with previous findings about population expansion in response to the Pleistocene climatic change, thus revealing the importance of this historical event in shaping the genetic structure and diversity of Southeast Asian mainland species.