Population genetics studies of Anopheles funestus, an important vector of malaria in sub-Saharan Africa, have largely been ignored. This is partially due to the lack of successful rearing in laboratory settings and the apparent success of insecticide campaigns. Previous studies have shown contradictory data regarding population structure(s)of An. funestus. 

Bcl-2 related proteins play an important role in regulating apoptosis through interactions with other Bcl-2-related proteins, as well as at the level of the mitochondrial membrane.  Bcl-2-related Ovarian Killer (Bok) is a proapoptotic family member previously shown to bind to Mcl-1, a rapidly regulated anti-apoptotic protein, via the BH3 domain.  Moreover, Bok has the capacity to integrate within the mitochondrial membrane via an alpha helical channel formation domain.  In the present experiments, the chicken (ch) bok cDNA was cloned and sequenced.  Compared to human bok, the nucleic acid sequence for the full coding region is 81% identical, while the deduced amino acid sequence is 80% identical (88% similar). Consistent with other death inducing Bcl-2-related proteins, ch Bok contains three of the four conserved Bcl-2 homology domains (BH1, 2, and 3).  A functional splicing variant (Bok-S) previously reported in the rat has a deletion including portions of the BH3 and BH1 domains which effectively eliminates the ability of Bok to interact with Mcl-1.  This splicing variant was not detected in the ch bok transcript as determined by PCR amplification.  Western blot analysis showed Bok protein to be highly expressed within reproductive tissues of the hen, with highest levels in the ovarian theca, stroma, post-ovulatory follicle, oviduct and shell gland, but very low to nondetectable levels within the granulosa layer.  Interestingly, the mRNA transcript was also expressed in in the brain, spleen, kidney and bone marrow.  Based upon previous reports in the rat, it was hypothesized that Bok plays an important role in follicular atresia in the hen ovary.  Therefore, experiments were conducted to evaluate patterns of Bok expression.  During follicle development, bok mRNA is expressed at slightly higher levels in granulosa from small follicles as compared to large, but Bok protein was not detectable.  In the theca, both the mRNA transcript and protein were increased in preovulatory (versus prehierarchal) follicles, and both were higher than in the granulosa layer.  Bok protein expression tended to increase, in vivo, in atretic versus normal follicles, and these results were duplicated with an in vitro system consisting of whole prehierarchal follicles incubated for three hours.  Finally, an attempt was made to regulate Bok expression in the ovary through incubations in the absence and presence of physiological agents, but no protein or mRNA regulation was detected in theca or granulosa.  Taken together, these experiments demonstrate that Bok mRNA and protein levels are not acutely regulated during the process of follicular atresia, in vivo or in vitro.  Moreover, the data suggest that, unlike the rat, Bok may not play a major proapoptotic role in hen granulosa cells.  Finally, the apparent lack of regulation in granulosa and theca tissues suggests that cellular relocalization of constitutively expressed Bok protein may be a critical step in facilitating any proapoptotic actions.

Double-stranded RNA (dsRNA) is capable of directing the sequence-specific degradation of mRNA by a process known as RNA interference (RNAi).  Thus, RNAi can effectively block the phenotypic expression of a target gene without affecting the stability of unrelated mRNA.  This phenomenon provides a powerful tool for creating loss-of-function mutant phenocopies of an organism.  If RNAi can be induced in the mosquito Anopheles gambiae, the major vector of the malaria parasite, then specific loss-of-function mutants can be reared and used in the development of a species-specific insecticide.  This end-goal is particularly important given that efforts to control malaria, the world's most prevalent insect-borne disease, are becoming increasingly hampered as the malaria parasite and its mosquito vectors develop resistance to anti-malarial drugs and insecticides.  To initiate the study of RNAi in An. gambiae, a foldback construct of the cloned Drosophila melanogaster eye color gene, cinnabar, was made using the multiple cloning site of the phagemid vector, pBC KS+.Once inserted into the pHermes[A5CEGFP] vector, this construct will be capable of forming hairpin dsRNA in vivo.  The design of this experiment calls for the microinjection of the pHermes[A5CEGFP]-cinnabar foldack construct into the embryos of a D. melanogaster strain carrying the brown mutation.  In these flies, the pteridine eye pigment biosynthesis pathway (responsible for all red pigments) has been knocked out, leaving only the ommochrome eye pigment biosynthesis pathway (responsible for all brown pigments).  The working hypothesis is that the foldback cinnabar sequence will prevent the phenotypic expression of the ommochrome pathway by RNAi, resulting in the reduction or complete loss of the eye color in the flies.  The eye color mutation provides a non-lethal and readily scorable means of detecting RNAi.  If the cinnabar construct proves to be functional and able to induce RNAi in D. melanogaster, an organism in which RNAi is already known to function, it will then be used to test for the presence of RNAi in a strain of Aedes aegypti with a loss-of-function mutation in its own cinnabar gene that was made transgenic using the D. melanogaster cinnabar gene as a marker.  Should RNAi be successfully induced in Ae. aegypti using the pHermes[A5CEGFP]-cinnabar foldback construct, the existence of RNAi in An. gambiae will then be tested for.

norpA is a recessive mutation in Drosophila that leads to retinal degeneration in adulthood.  This study was completed to analyze various ways to suppress retinal degeneration in norpA mutant flies and to gain a better understanding of the norpA cell death pathway.  Several experiments were done to determine 1) if p35 could suppress norpA induced cell death, 2) if the levels of expression of p35 affected the suppression of norpA, 3) if new genes could be isolated that are downstream of norpA, and 4) if a critical period for the rescue of norpA mutants could be determined.  norpA was found to be partially suppressed by p35 although hid, a gene known to be an activator of apoptosis, was completely suppressed by p35.  The results of these experiments showed that norpA is undergoing a caspase mediated cell death. However, there is a possibility that another death mechanism may be involved since P35 only delayed, but did not prevent, degeneration in norpA.   The difference in the suppression of norpA and hid is not due to loss of protein expression of p35 in adulthood, assayed by Western Blot analysis. Finding new genes involved in the norpA degeneration cascade through a mutagenesis screen will help elucidate the mechanisms of programmed cell death caused by norpA.

Mycobacterium avium is an intracellular pathogen that has been shown to remain localized in an early phagosomal compartment that acquires early endosome characteristics.  ARF6 (ADP ribosylation factor 6), a small molecular weight GTPase of the Ras superfamily, has been localized to the early endosome and regulates the recycling of endosomes to the cell surface.  We are interested in examining the role of ARF6 in the uptake and intracellular fate of mycobacteria in macrophages.  To this end, using the retrovirus expression system we transiently expressed epitope tagged-wild type ARF6 and ARF6 mutants defective in GTP binding and hydrolysis in primary bone marrow macrophages.  Our preliminary findings have revealed that ARF6 may regulate the adhesive properties and mycobacterial invasion of macrophages.

Mycobacteria are important human pathogens and include M. tuberculosis, M. avium, and M. leprae.  M. tuberculosis, the etiological agent of tuberculosis, is responsible for an estimated three-million deaths annually.  All pathogenic strains of mycobacteria, including M. tuberculosis, live and multiply inside macrophages.  The mycobacteria enter the macrophage through conventional phagocytosis and remain within tightly bound phagosomes.  The survival of these bacteria is dependent on the ability of the mycobacteria to inhibit the normal phagosome-lysosome fusion.  However, the mechanism by which the mycobacteria inhibit this fusion process remains obscure.  We hypothesize that the cellular signaling processes are modulated differently upon macrophage-mycobacterial interaction compared to other macrophage and particle interactions, and these differences play an essential role in mycobacteria’s ability to inhibit the phagosome-lysosome fusion. We investigate one part of the signaling pathway that is activated due to mycobacterium-macrophage interactions.  Using macrophages from SRC-knockout mice, we explore the role that SRC kinases play in the signaling and survival of mycobacteria inside the macrophage using strains of M. avium, an opportunistic bacteria that commonly infects AIDS patients.  Members of the SRC kinase family include hck, lyn, and fgr and are key signaling molecules in macrophages, known to regulate signaling via the growth factor and Fc receptors.  Hck kinase has also been shown to be essential for the fusion of azurophil granules with the phagosome in human neutrophils, and its modulation may also play a role in the survival of mycobacteria in macrophages.  We have found that the SRC kinases are not essential for mycobacterial phagocytosis, with no difference seen in mycobacterial uptake between wild type control macrophages and SRC-knockout macrophages.  SRC-kinases are also not essential mediators of phagocytosis via the complement receptors.  Their absence has no effect on mycobacterial survival and minimal effect on mycobacterial mediated activation of the MAP kinases.

Cytoplasmic dynein is the predominant minus?end directed microtubule motor in eukaryotic cells, and is responsible for centripetal transport of several membrane classes including late endosomes, lysosomes, and the Golgi apparatus.  This large multi-subunit protein is composed of heavy chains (HCs), which contain the motor activity of the complex, intermediate chains (ICs) which are responsible for targeting and light intermediate chains (LICs) and light chains (LCs) of unknown function. In previous work, the ICs were shown to bind directly to p150^Glued, implicating the dynactin complex as an adaptor or receptor for cytoplasmic dynein on membranes. To test the essential nature of the IC-p150^Glued interaction, we generated a molecular chimera between the p150^Glued-binding domain of the ICs and the motor domain of the minus end-directed kinesin homologue cho2. This molecule is predicted to compete with native cytoplasmic dynein for membrane binding, and to disrupt membrane transport.  However, because cho2 is also a microtubule motor protein, this chimera might retain membrane transport function.  As an initial step in our analysis of this novel chimera, we expressed the construct in mammalian cells and tested for defects in membrane transport.  The GFP-tagged IC-cho2 chimera was largely soluble with a subset targeted to microtubules. This suggests that the chimera has retained some degree of motor activity.  When Golgi transport was examined using either GFP-NAGT or an antibody to foriminotransferase cyclodeaminase (a 58kD), we observed Golgi dispersal in a significant fraction of transfected cells, reflecting inhibition of dynein-mediated transport.  When late endosome and lysosome transport were examined using rhodamine-dextran, very little net centripetal transport was detected, also suggesting inhibition.  Together these findings suggest that our IC-cho2 chimera exhibits some dominant inhibitory effects on dynein-mediated transport, and will be useful for our analysis of dynein function and phosphorylation.  In future studies we will test the cho2-dependent motor activity of this construct, and the effects of mutations in IC phosphorylation sites.

Several zebrafish mutants characterized by defects in the ocular lens were identified from a chemical mutagenesis screen.  One of those mutants, line 3014, revealed a potential failure in lens tissue differentiation that resulted in lens degeneration at 72 hours post fertilization (hpf).  To begin definition of the molecular basis of the 3014 mutant phenotype, the expression patterns of two transcription factors, Prox 1 and Pax 6, known to play important roles in lens development, were examined using immunohistochemistry and in situ mRNA hybridization.  Wild-type and 3014 mutant embryos at 24 hpf and 72 hpf were incubated in polyclonal rabbit prox 1 antibody and visualized with fluorescein-conjugated anti-rabbit antibody.  At 24 hpf, Prox 1 protein expression was restricted to the lens epithelial cells in both mutant and wild-type embryos.  At 72 hpf, wild-type embryos expressed Prox 1 only in the retina, while the 3014 mutant embryos expressed Prox 1 in both the retina and some remaining lens cells.  In preparation for in situ mRNA hybridization studies on whole-mount embryos, wild-type 24 hpf embryos were probed with Pax 6 DIG-labeled RNA.  As expected, Pax 6 expression was detected in the eye and lens tissue of wild-type embryos.  Further studies will examine Pax 6 expression in the 3014 mutants.  In addition, we began analyzing microsatellite primer pairs to identify amplification products that segregate with the 3014 mutation to obtain a molecular marker for further phenotypic studies and to map the mutation’s chromosomal location.


 
 

     1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3], the active metabolite of vitamin D, is a potent inhibitor of breast cancer cell growth both in vivo and in vitro.  It has been established that 1,25-(OH)2D3 induces growth arrest and apoptosis in MCF-7 cells.  To investigate the mechanisms by which 1,25-(OH)2D3 activates apoptosis a 1,25-(OH)2D3 resistant variant (MCF-7D3Res) was selected by continuous culture of MCF-7 cells in 100nM 1,25-(OH)2D3  .MCF-7D3Res cells are a novel cell line that have a functional apoptotic pathway but are selectively insensitive to the growth regulatory properties of 1,25-(OH)2D3 and structurally related analogs.  The MCF-7D3Res cells offer a unique model system for identification of the mechanisms by which vitamin D regulates the cell death pathway in breast cancer cells.  Although no phenotypic differences have been found between these two cell lines, it has been shown that estradiol differentially enhances sensitivity of MCF-7 wt cells to 1,25-(OH)2D3 mediated transcriptional activity, suggesting that anti-estrogens might interfere with the actions of Vitamin D and its analogs.

Although 1a,25 dihydroxyvitamin D₃ (1a,25(OH)₂D₃) is a coordinate regulator of proliferation and apoptosis of breast cancer cells in vitro and in vivo, its effects on normal mammary tissue are unclear.  The vitamin D₃ receptor (VDR) is expressed in mammary epithelial cells, and 1a,25(OH)₂D₃ and its analogs can suppress the development of mammary tumors in animal models. To define the potential role of the VDR in mammary gland development and tumorigenesis, we assessed mammary gland development in Vitamin D Receptor knockout mice (provided by Dr. Marie Demay, Harvard).  Development of the pubertal mammary gland was compared in VDR knockout (-/-) and wild type (+/+) mice, which were fed a high calcium rescue diet to prevent disturbances in calcium and bone homeostasis.  Comparison was made in reference to the number of terminal end buds (TEB) and the degree of branching within each gland. TEBs are highly proliferating structures that rapidly penetrate the stromal fat pad and serve as precursors of ductal morphogenesis.  Analysis of inguinal mammary gland whole mounts indicated a significant increase in TEB number at 6 weeks of age in VDR (-/-) mice compared to age and weight matched (+/+) mice.  The increased TEB number in VDR (-/-) mice appeared to reflect a reduction in the differentiation of the TEBs when compared to the (+/+) mice, although the ductal development as well as the degree of branching where essentially equivalent in both (+/+) and (-/-) glands throughout development.  In addition, histological assessment of proliferating cell nuclear antigen (PCNA) and in situ terminal transferase mediated dUTP nick end labeling (TUNEL), identified proliferating and apoptotic cells during ductal development in -/- and +/+ mammary glands.  Body weights of the VDR (-/-) and (+/+) mice were equivalent, indicating that increased TEB number in VDR (-/-) glands was not due to increased body size.  These data indicate that VDR knockout mice exhibit a delay in TEB differentiation, and suggest that 1a,25(OH)₂D₃ mediated gene expression influences ductal morphogenesis during the pubertal stages of development.

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