Steroid signaling controls sex-specific development in an invertebrate.

In vertebrate sexual development, two important steroid hormones, testosterone and estrogen, regulate the sex-specific development of many tissues. In contrast, invertebrates utilize a single steroid hormone, ecdysone, to regulate developmental timing in both sexes. However, here we show that in Drosophila melanogaster, sex-specific ecdysone (E) signaling controls important aspects of gonad sexual dimorphism. Rather than being regulated at the level of hormone production, hormone activity is regulated cell-autonomously through sex-specific hormone reception. Ecdysone receptor (EcR) expression is restricted to the developing ovary and is repressed in the testis at a time when ecdysone initiates ovary morphogenesis. Interestingly, EcR expression is regulated downstream of the sex determination factor Doublesex (Dsx), the founding member of the Dsx/Mab3 Related Transcription Factor (DMRT) family that regulates gonad development in all animals. E signaling is required for normal ovary development1,2, and ectopic activation of E signaling in the testis antagonized stem cell niche identity and feminized somatic support cells, which were transformed into follicle-like cells. This work demonstrates that invertebrates can also use steroid hormone signaling to control sex-specific development. Further, it may help explain recent work showing that vertebrate sexual development is surprisingly cell-autonomous. For example, chickens utilize testosterone and estrogen to control sex-specific development, but when they have a mixture of cells with male and female genotypes, the male cells develop as male and the female cells develop as female despite exposure to the same circulating hormones3. Sex-specific regulation of steroid hormone signaling may well underly such cell-autonomous sexual fate choices in vertebrates as it does in Drosophila.

Control of a Novel Spermatocyte-Promoting Factor by the Male Germline Sex Determination Factor PHF7 of Drosophila melanogaster.

A key aspect of germ cell development is to establish germline sexual identity and initiate a sex-specific developmental program to promote spermatogenesis or oogenesis. Previously, we have identified the histone reader Plant Homeodomain Finger 7 (PHF7) as an important regulator of male germline identity. To understand how PHF7 directs sexual differentiation of the male germline, we investigated the downstream targets of PHF7 by combining transcriptome analyses, which reveal genes regulated by Phf7, with genomic profiling of histone H3K4me2, the chromatin mark that is bound by PHF7. Through these genomic experiments, we identify a novel spermatocyte factor Receptor Accessory Protein Like 1 (REEPL1) that can promote spermatogenesis and whose expression is kept off by PHF7 in the spermatogonial stage. Loss of Reepl1 significantly rescues the spermatogenesis defects in Phf7 mutants, indicating that regulation of Reepl1 is an essential aspect of PHF7 function. Further, increasing REEPL1 expression facilitates spermatogenic differentiation. These results indicate that PHF7 controls spermatogenesis by regulating the expression patterns of important male germline genes.

Health and wellness photovoice project: engaging consumers with serious mental illness in health care interventions.

People with serious mental illnesses (SMI) are at increased risk for cardiovascular disease and premature mortality. We used photovoice in two supportive housing agencies to engage consumers with SMI to inform the implementation of health care interventions. Sixteen consumers participated in six weekly sessions in which they took photographs about their health and discussed the meanings of these photographs in individual interviews and group sessions. We identified several implementation themes related to consumers' preferences. Peer-based approaches were preferred more than clinician-driven models. Participants expressed a desire to learn practical skills through hands-on activities to modify health behaviors. Consumers expressed a desire to increase their physical activity. Participants revealed in their photographs and narratives the important role that communities' food environments play in shaping eating habits. In this article, we show how photovoice can generate valuable community knowledge to inform the translation of health care interventions in supportive housing agencies.

Phf7 controls male sex determination in the Drosophila germline.

Establishment of germline sexual identity is critical for production of male and female germline stem cells, as well as sperm versus eggs. Here we identify PHD Finger Protein 7 (PHF7) as an important factor for male germline sexual identity in Drosophila. PHF7 exhibits male-specific expression in early germ cells, germline stem cells, and spermatogonia. It is important for germline stem cell maintenance and gametogenesis in males, whereas ectopic expression in female germ cells ablates the germline. Strikingly, expression of PHF7 promotes spermatogenesis in XX germ cells when they are present in a male soma. PHF7 homologs are also specifically expressed in the mammalian testis, and human PHF7 rescues Drosophila Phf7 mutants. PHF7 associates with chromatin, and both the human and fly proteins bind histone H3 N-terminal tails with a preference for dimethyl lysine 4 (H3K4me2). We propose that PHF7 acts as a conserved epigenetic "reader" that activates the male germline sexual program.

Macrocyclic BACE inhibitors: Optimization of a micromolar hit to nanomolar leads.

We have identified macrocyclic inhibitors of the aspartic protease BACE, implicated in the etiology of Alzheimer's disease. An X-ray structure of screening hit 1 in the BACE active site revealed a hairpin conformation suggesting that constrained macrocyclic derivatives may also bind there. Several of the analogs we prepared were >100x more potent than 1, such as 7 (5 nM K(i)).

2-Amino-3,4-dihydroquinazolines as inhibitors of BACE-1 (beta-site APP cleaving enzyme): Use of structure based design to convert a micromolar hit into a nanomolar lead.

A new aspartic protease inhibitory chemotype bearing a 2-amino-3,4-dihydroquinazoline ring was identified by high-throughput screening for the inhibition of BACE-1. X-ray crystallography revealed that the exocyclic amino group participated in a hydrogen bonding array with the two catalytic aspartic acids of BACE-1 (Asp(32), Asp(228)). BACE-1 inhibitory potency was increased (0.9 microM to 11 nM K(i)) by substitution into the unoccupied S(1)' pocket.

Genomic organization of gypsy chromatin insulators in Drosophila melanogaster.

Chromatin insulators have been implicated in the regulation of higher-order chromatin structure and may function to compartmentalize the eukaryotic genome into independent domains of gene expression. To test this possibility, we used biochemical and computational approaches to identify gypsy-like genomic-binding sites for the Suppressor of Hairy-wing [Su(Hw)] protein, a component of the gypsy insulator. EMSA and FISH analyses suggest that these are genuine Su(Hw)-binding sites. In addition, functional tests indicate that genomic Su(Hw)-binding sites can inhibit enhancer-promoter interactions and thus function as bona fide insulators. The insulator strength is dependent on the genomic location of the transgene and the number of Su(Hw)-binding sites, with clusters of two to three sites showing a stronger effect than individual sites. These clusters of Su(Hw)-binding sites are located mostly in intergenic regions or in introns of large genes, an arrangement that fits well with their proposed role in the formation of chromatin domains. Taken together, these data suggest that genomic gypsy-like insulators may provide a means for the compartmentalization of the genome within the nucleus.

Linear interaction energy models for beta-secretase (BACE) inhibitors: Role of van der Waals, electrostatic, and continuum-solvation terms.

Computing the binding affinity of a protein-ligand complex is one of the most fundamental and difficult tasks in computer-aided drug design. Many approaches for computing binding affinities can be classified as linear interaction energy (LIE) models as they rely on some type of linear fit of computed interaction energies between ligand and protein. We have examined the computed interaction energies of a series of beta-secretase (BACE) inhibitors in terms of van der Waals, coulombic, and continuum-solvation contributions to ligand binding. We have also systematically examined the effect of different protonation states of the protein and ligands. We find that the binding affinities are relatively insensitive to the protonation state of the protein when neutral ligands are considered. Inclusion of charged ligands leads to large deviations in the coulomb, solvation, and even van der Waals terms. The latter is due to increased repulsive van der Waals interactions in the complex due to the strong coulomb attraction found between oppositely charged functional groups in the protein and ligand. In general, we find that the best models are obtained when the protein is judiciously charged (e.g. Asp32-, Arg235+) and the potentially charged ligands are treated as neutral.

The role of histone H2Av variant replacement and histone H4 acetylation in the establishment of Drosophila heterochromatin.

Activation and repression of transcription in eukaryotes involve changes in the chromatin fiber that can be accomplished by covalent modification of the histone tails or the replacement of the canonical histones with other variants. Here we show that the histone H2A variant of Drosophila melanogaster, H2Av, localizes to the centromeric heterochromatin, and it is recruited to an ectopic heterochromatin site formed by a transgene array. His2Av behaves genetically as a PcG gene and mutations in His2Av suppress position effect variegation (PEV), suggesting that this histone variant is required for euchromatic silencing and heterochromatin formation. His2Av mutants show reduced acetylation of histone H4 at Lys 12, decreased methylation of histone H3 at Lys 9, and a reduction in HP1 recruitment to the centromeric region. H2Av accumulation or histone H4 Lys 12 acetylation is not affected by mutations in Su(var)3-9 or Su(var)2-5. The results suggest an ordered cascade of events leading to the establishment of heterochromatin and requiring the recruitment of the histone H2Av variant followed by H4 Lys 12 acetylation as necessary steps before H3 Lys 9 methylation and HP1 recruitment can take place.

Emerging beta-amyloid therapies for the treatment of Alzheimer's disease.

Alzheimer's Disease (AD) is a progressive neurodegenerative disorder marked by loss of memory, cognition, and behavioral stability. AD is defined pathologically by extracellular neuritic plaques comprised of fibrillar deposits of beta-amyloid peptide (Abeta) and neurofibrillary tangles comprised of paired helical filaments of hyperphosphorylated tau. Current therapies for AD, such as cholinesterase inhibitors, treat the symptoms but do not modify the progression of the disease. The etiology of AD is unclear. However, data from familial AD mutations (FAD) strongly support the "amyloid cascade hypothesis" of AD, i.e. that neurodegeneration in AD is initiated by the formation of neurotoxic beta-amyloid (Abeta) aggregates; all FAD mutations increase levels of Abeta peptide or density of Abeta deposits. The likely link between Abeta aggregation and AD pathology emphasizes the need for a better understanding of the mechanisms of Abeta production. This review summarizes current therapeutic strategies directed at lowering Abeta levels and decreasing levels of toxic Abeta aggregates through (1) inhibition of the processing of amyloid precursor protein (APP) to Abeta peptide, (2) inhibition, reversal or clearance of Abeta aggregation, (3) cholesterol reduction and (4) Abeta immunization.

Trans-splicing as a novel mechanism to explain interallelic complementation in Drosophila.

Two mutant alleles of the same gene, each located in one of the two homologous chromosomes, may in some instances restore the wild-type function of the gene. This is the case with certain combinations of mutant alleles in the mod(mdg4) gene. This gene encodes several different proteins, including Mod(mdg4)2.2, a component of the gypsy insulator. This protein is encoded by two separate transcription units that can be combined in a trans-splicing reaction to form the mature Mod(mdg4)2.2-encoding RNA. Molecular characterization of complementing alleles shows that they affect the two different transcription units. Flies homozygous for each allele are missing the Mod(mdg4)2.2 protein, whereas wild-type trans-heterozygotes are able to synthesize almost normal levels of the Mod(mdg4)2.2 product. This protein is functional as judged by its ability to form a functional insulator complex. The results suggest that the interallelic complementation in the mod(mdg4) gene is a consequence of trans-splicing between two different mutant transcripts. A conclusion from this observation is that the trans-splicing reaction that takes place between transcripts produced on two different mutant chromosomes ensures wild-type levels of functional protein.

The new mendicancy: homeless in New York City.

An ethnographic study of the homeless poor in New York City suggests that significant changes have taken place in the size and composition of that population during the past 15 years. Among the disenfranchised, the mentally disabled figure prominently, many of them casualties of state deinstitutionalization and restricted admission policies. This paper argues that in the absence of safe and accessible shelter, rehabilitation efforts are doomed to failure. It is suggested that clinicians could play a critical advocacy role for an approach that sees therapeutic and social needs as intimately linked.