Direct role of Bardet-Biedl syndrome proteins in transcriptional regulation.

Primary cilia are conserved organelles that play crucial roles as mechano- and chemosensors, as well as transducing signaling cascades. Consequently, ciliary dysfunction results in a broad range of phenotypes: the ciliopathies. Bardet-Biedl syndrome (BBS), a model ciliopathy, is caused by mutations in 16 known genes. However, the biochemical functions of the BBS proteins are not fully understood. Here we show that the BBS7 protein (localized in the centrosomes, basal bodies and cilia) probably has a nuclear role by virtue of the presence of a biologically confirmed nuclear export signal. Consistent with this observation, we show that BBS7 interacts physically with the polycomb group (PcG) member RNF2 and regulate its protein levels, probably through a proteasome-mediated mechanism. In addition, our data supports a similar role for other BBS proteins. Importantly, the interaction with this PcG member is biologically relevant because loss of BBS proteins leads to the aberrant expression of endogenous RNF2 targets in vivo, including several genes that are crucial for development and for cellular and tissue homeostasis. Our data indicate a hitherto unappreciated, direct role for the BBS proteins in transcriptional regulation and potentially expand the mechanistic spectrum that underpins the development of ciliary phenotypes in patients.

SOD1G93A Astrocyte-Derived Extracellular Vesicles Induce Motor Neuron Death by a miRNA-155-5p-Mediated Mechanism.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by upper and lower motor neuron (MN) degeneration. Astrocytes surrounding MNs are known to modulate ALS progression. When cocultured with astrocytes overexpressing the ALS-linked mutant Cu/Zn superoxide dismutase (SOD1G93A) or when cultured with conditioned medium from SOD1G93A astrocytes, MN survival is reduced. The exact mechanism of this neurotoxic effect is unknown. Astrocytes secrete extracellular vesicles (EVs) that transport protein, mRNA, and microRNA species from one cell to another. The size and protein markers characteristic of exosomes were observed in the EVs obtained from cultured astrocytes, indicating their abundance in exosomes. Here, we analyzed the microRNA content of the exosomes derived from SOD1G93A astrocytes and evaluated their role in MN survival. Purified MNs exposed to SOD1G93A astrocyte-derived exosomes showed reduced survival and neurite length compared to those exposed to exosomes derived from non-transgenic (non-Tg) astrocytes. Analysis of the miRNA content of the exosomes revealed that miR-155-5p and miR-582-3p are differentially expressed in SOD1G93A exosomes compared with exosomes from non-Tg astrocytes. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicates that miR-155-5p and miR-582-3p predicted targets are enriched in the neurotrophin signaling pathway. Importantly, when levels of miR-155-5p were reduced by incubation with a specific antagomir, SOD1G93A exosomes did not affect MN survival or neurite length. These results demonstrate that SOD1G93A-derived exosomes are sufficient to induce MN death, and miRNA-155-5p contributes to this effect. miRNA-155-5p may offer a new therapeutic target to modulate disease progression in ALS.

Trypanosoma cruzi Isolates Naturally Adapted to Congenital Transmission Display a Unique Strategy of Transplacental Passage.

Chagas disease is mainly transmitted by vertical transmission (VT) in nonendemic areas and in endemic areas where vector control programs have been successful. For the present study, we isolated natural Trypanosoma cruzi strains vertically transmitted through three generations and proceeded to study their molecular mechanism of VT using mice. No parasitemia was detected in immunocompetent mice, but the parasites were able to induce an immune response and colonize different organs. VT experiments revealed that infection with different strains did not affect mating, pregnancy, or resorption, but despite low parasitemia, VT strains reached the placenta and resulted in higher vertical transmission rates than strains of either moderate or high virulence. While the virulent strain modulated more than 2,500 placental genes, VT strains modulated 150, and only 29 genes are shared between them. VT strains downregulated genes associated with cell division and replication and upregulated immunomodulatory genes, leading to anti-inflammatory responses and tolerance. The virulent strain stimulated a strong proinflammatory immune response, and this molecular footprint correlated with histopathological analyses. We describe a unique placental response regarding the passage of T. cruzi VT isolates across the maternal-fetal interphase, challenging the current knowledge derived mainly from studies of laboratory-adapted or highly virulent strains. IMPORTANCE The main findings of this study are that we determined that there are Trypanosoma cruzi strains adapted to transplacental transmission and completely different from the commonly used laboratory reference strains. This implies a specific strategy for the vertical transmission of Chagas disease. It is impressive that the strains specialized for vertical transmission modify the gene expression of the placenta in a totally different way than the reference strains. In addition, we describe isolates of T. cruzi that cannot be transmitted transplacentally. Taken together, these results open up new insights into the molecular mechanisms of this insect vector-independent transmission form.

Modulation of gene expression during early stages of reconnection of the turtle spinal cord.

The spinal cord of the freshwater turtle Trachemys dorbignyi regenerates after complete transection (Rehermann et al. J. Comp. Neurol. 515, 2009, 197-214). This remarkable ability may be related to the persistence around the central canal (CC) of progenitors functionally clustered via connexin 43 (Cx43) that express brain lipid binding protein (BLBP) and the transcription factor Pax6 (Russo et al. J. Neurosci. 28, 2008, 8510-8516). Indeed, because BLBP+ cells appear in the bridge joining the rostral and caudal stumps, we speculated that progenitors contacting the central canal may play a key part in spinal cord regeneration. To test this hypothesis, we designed degenerated primers pairing conserved regions for key proteins synthesized in progenitors (BLBP, Cx43, and Pax6) and the neuronal protein HuB. Fragments of these proteins were amplified, cloned, and sequenced. Based on these sequences, we analyzed the changes in the expression levels using quantitative real-time RT-PCR with specific primers, comparing the injured spinal cord at different times after injury (4, 12, 20, and 60 days) with uninjured spinal cords. We found a transient, early increase of BLBP, Cx43 and HuB mRNA, with Pax6 remaining unchanged. These results suggest that the selected genes--active in progenitor cells--play an important part in early mechanisms of spinal cord regeneration.

Host-parasite interaction: changes in human placental gene expression induced by Trypanosoma cruzi.

BACKGROUND: Chagas disease is caused by Trypanosoma cruzi, a parasite endemic to Latin America. Most infections occur in children by vector or congenital transmission. Trypanosoma cruzi establishes a complexity of specific molecular parasite-host cell interactions to invade the host. However, most studies have been mainly focused on the interaction between the parasite and different cell types, but not on the infection and invasion on a tissue level. During congenital transmission, T. cruzi must cross the placental barrier, composed of epithelial and connective tissues, in order to infect the developing fetus. Here we aimed to study the global changes of transcriptome in the placental tissue after a T. cruzi challenge. RESULTS: Strong changes in gene expression profiling were found in the different experimental conditions, involving the reprogramming of gene expression in genes involved in the innate immune response. CONCLUSIONS: Trypanosoma cruzi induces strong changes in genes involved in a wide range of pathways, especially those involved in immune response against infections.

MUC5B silencing reduces chemo-resistance of MCF-7 breast tumor cells and impairs maturation of dendritic cells.

Mucins participate in cancer progression by regulating cell growth, adhesion, signaling, apoptosis or chemo-resistance to drugs. The secreted mucin MUC5B, the major component of the respiratory tract mucus, is aberrantly expressed in breast cancer, where it could constitute a cancer biomarker. In this study we evaluated the role of MUC5B in breast cancer by gene silencing the MUC5B expression with short hairpin RNA on MCF-7 cells. We found that MUC5B-silenced MCF-7 cells have a reduced capacity to grow, adhere and form cell colonies. Interestingly, MUC5B knock-down increased the sensitivity to death induced by chemotherapeutic drugs. We also show that MUC5B silencing impaired LPS-maturation of DCs, and production of cytokines. Furthermore, MUC5B knock-down also influenced DC-differentiation and activation since it resulted in an upregulation of IL-1ß, IL-6 and IL-10, cytokines that might be involved in cancer progression. Thus, MUC5B could enhance the production of LPS-induced cytokines, suggesting that the use of MUC5B-based cancer vaccines combined with DC-maturation stimuli, could favor the induction of an antitumor immune response.

Dissecting chronic lymphocytic leukemia microenvironment signals in patients with unmutated disease: microRNA-22 regulates phosphatase and tensin homolog/AKT/FOXO1 pathway in proliferative leukemic cells.

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of clonal B cells arrested in G0/G1 stages that coexist with proliferative B cells. We identified one of these proliferative subsets in the peripheral blood from patients with unmutated disease (UM). Aiming to characterize the molecular mechanism underlying this proliferative behavior, we performed gene expression analysis of the mRNA and microRNAs in this leukemic subpopulation and compared results with those for the quiescent counterpart. Our results suggest that proliferation of this subset mainly depends on microRNA-22 overexpression, which induces phosphatase and tensin homolog (PTEN) down-regulation and phosphoinositide 3-kinase (PI3K)/AKT pathway activation. These results underline the role of the PI3K/AKT pathway at the origin of this proliferative pool in patients with UM CLL and provide additional rationale for the use of PI3K inhibitors.

Early Trypanosoma cruzi infection reprograms human epithelial cells.

Trypanosoma cruzi, the causative agent of Chagas disease, has the peculiarity, when compared with other intracellular parasites, that it is able to invade almost any type of cell. This property makes Chagas a complex parasitic disease in terms of prophylaxis and therapeutics. The identification of key host cellular factors that play a role in the T. cruzi invasion is important for the understanding of disease pathogenesis. In Chagas disease, most of the focus is on the response of macrophages and cardiomyocytes, since they are responsible for host defenses and cardiac lesions, respectively. In the present work, we studied the early response to infection of T. cruzi in human epithelial cells, which constitute the first barrier for establishment of infection. These studies identified up to 1700 significantly altered genes regulated by the immediate infection. The global analysis indicates that cells are literally reprogrammed by T. cruzi, which affects cellular stress responses (neutrophil chemotaxis, DNA damage response), a great number of transcription factors (including the majority of NF κ B family members), and host metabolism (cholesterol, fatty acids, and phospholipids). These results raise the possibility that early host cell reprogramming is exploited by the parasite to establish the initial infection and posterior systemic dissemination.