During interphase centromeres often coalesce into a small number of chromocenters, which can be visualized as distinct, DAPI dense nuclear domains. Intact chromocenters play a major role in maintaining genome stability as they stabilize the transcriptionally silent state of repetitive DNA while ensuring centromere function. Despite its biological importance, relatively little is known about the molecular composition of the chromocenter or the processes that mediate chromocenter formation and maintenance. To provide a deeper molecular insight into the composition of the chromocenter and to demonstrate the usefulness of proximity-based biotinylation as a tool to investigate those questions, we performed super resolution microscopy and proximity-based biotinylation experiments of three distinct proteins associated with the chromocenter in Drosophila. Our work revealed an intricate internal architecture of the chromocenter suggesting a complex multilayered structure of this intranuclear domain.

Hybrid incompatibility between Drosophila melanogaster and D. simulans is caused by a lethal interaction of the proteins encoded by the Hmr and Lhr genes. In D. melanogaster the loss of HMR results in mitotic defects, an increase in transcription of transposable elements and a deregulation of heterochromatic genes. To better understand the molecular mechanisms that mediate HMR’s function, we measured genome-wide localization of HMR in D. melanogaster tissue culture cells by chromatin immunoprecipitation. Interestingly, we find HMR localizing to genomic insulator sites that can be classified into two groups. One group belongs to gypsy insulators and another one borders HP1a bound regions at active genes. The transcription of the latter group genes is strongly affected in larvae and ovaries of Hmr mutant flies. Our data suggest a novel link between HMR and insulator proteins, a finding that implicates a potential role for genome organization in the formation of species.

During a four year period, a total of 84 cases of dermatophytosis were seen in patients from 0 to 17 years of age attending our out-patient department. The sex distribution was about equal in preadolescents. Males predominated among adolescents. A peak incidence at early school age was due to cases of tinea capitis, mainly caused by Microsporum canis. A peak among adolescents was due to cases of tinea pedis, mainly caused by Trichophyton rubrum. In general, patients with Trichophyton rubrum infections were older than those with other types of dermatophytosis (p less than 0.05). Dermatophytosis due to Microsporum canis was most frequently seen in January and in September (p less than 0.01). Although onychomycosis due to dermatophytes was a comparatively rare disease, it did occur within all age subgroups. Entities which were very frequent in former times and which have become rare during the last decades, such as tinea capitis due to Trichophyton schönleinii, still contribute to the spectrum of dermatophytosis in childhood.

The relevance of intense protein binding to the antifungal activity of azole compounds is still a matter of debate. The influence of albumin on the antimicrobial activity of ketoconazole and itraconazole, which exhibit very strong plasma protein binding (99 and 99.8%), was evaluated in vitro. Candida albicans was exposed to continuously changing azole concentrations corresponding to drug levels in serum following an oral dose of 200 mg. Total as well as free drug levels in serum were simulated. The incubation medium was free of proteins or contained 4% human serum albumin. Itraconazole levels reflecting free drug concentrations in humans did not reduce the growth rate of C. albicans, as compared with controls (difference in the log CFU per milliliter at 12 h, 0.03 ± 0.09), whereas total drug levels were as active in the presence of 4% albumin (meah difference, -0.61) as in its absence (-0.75). The same was true for ketoconazole, except that free drug levels were also active (-1.21 versus -1.39 for total drug levels). This result was due to the higher ketoconazole levels in humans. Thus, in terms of routine susceptibility testing, in vitro total drug levels can be considered relevant.

Understanding the molecular basis of hybrid incompatibilities is a fundamental pursuit in evolutionary genetics. In crosses between Drosophila melanogaster females and Drosophila simulans males, an interaction between at least three genes is necessary for hybrid male lethality: Hmr mel, Lhr sim, and gfzf sim. Although HMR and LHR physically bind each other and function together in a single complex, the connection between gfzf and either of these proteins remains mysterious. Here, we show that GFZF localizes to many regions of the genome in both D. melanogaster and D. simulans, including at telomeric retrotransposon repeats. We find that GFZF localization at telomeres is significantly different between these two species, reflecting the rapid evolution of telomeric retrotransposon copy number composition between the two species. Next, we show that GFZF and HMR normally do not colocalize in D. melanogaster. In interspecies hybrids, however, HMR shows extensive mis-localization to GFZF sites, thus uncovering a new molecular interaction between these hybrid incompatibility factors. We find that spreading of HMR to GFZF sites requires gfzf sim but not Lhr sim, suggesting distinct roles for these factors in the hybrid incompatibility. Finally, we find that overexpression of HMR and LHR within species is sufficient to mis-localize HMR to GFZF binding sites, indicating that HMR has a natural low affinity for GFZF sites. Together, these studies provide the first insights into the different properties of gfzf between D. melanogaster and D. simulans, and uncover a molecular interaction between gfzf and Hmr in the form of altered protein localization.