The epigenetic modifiers 5-aza-2'-deoxycytidine and trichostatin A influence adipocyte differentiation in human mesenchymal stem cells

Epigenetic mechanisms such as DNA methylation and histone modification are important in stem cell differentiation. Methylation is principally associated with transcriptional repression, and histone acetylation is correlated with an active chromatin state. We determined the effects of these epigenetic mechanisms on adipocyte differentiation in mesenchymal stem cells (MSCs) derived from bone marrow (BM-MSCs) and adipose tissue (ADSCs) using the chromatin-modifying agents trichostatin A (TSA), a histone deacetylase inhibitor, and 5-aza-2′-deoxycytidine (5azadC), a demethylating agent. Subconfluent MSC cultures were treated with 5, 50, or 500 nM TSA or with 1, 10, or 100 µM 5azadC for 2 days before the initiation of adipogenesis. The differentiation was quantified and expression of the adipocyte genes PPARG and FABP4 and of the anti-adipocyte gene GATA2 was evaluated. TSA decreased adipogenesis, except in BM-MSCs treated with 5 nM TSA. Only treatment with 500 nM TSA decreased cell proliferation. 5azadC treatment decreased proliferation and adipocyte differentiation in all conditions evaluated, resulting in the downregulation of PPARG and FABP4 and the upregulation of GATA2. The response to treatment was stronger in ADSCs than in BM-MSCs, suggesting that epigenetic memories may differ between cells of different origins. As epigenetic signatures affect differentiation, it should be possible to direct the use of MSCs in cell therapies to improve process efficiency by considering the various sources available.

Proteomic analysis of metacyclic trypomastigotes undergoing Trypanosoma cruzi metacyclogenesis

Trypanosoma cruzi, the causative agent of the Chagas disease, has a complex life cycle alternating between replicative and noninfective forms with nonreplicative and infective forms of the parasite. Metacyclogenesis is a process that takes place in the invertebrate host, comprising morphogenetic transformation from a noninfective form to an infective form, such that parasites acquire the ability to invade human cells. We analyze here the metacyclogenesis process by 2D electrophoresis coupled to MALDI-TOF MS. A large proportion of unique proteins expressed during metacyclogenesis were observed. Interestingly, 50% of the spots were found to differ between epimastigotes and trypomastigotes. We provide a 2D map of the infective metacyclic trypomastigotes. Sixty six protein spots were successfully identified corresponding to 43 different proteins. We analyzed the expression profiles for the identified proteins along metacyclogenesis and classified them into three groups according to their maximal level of expression. We detected several isoforms for a number of proteins, some displaying differential expression during metacyclogenesis. These results suggest that posttranslational modifications may be a fundamental part of the parasite's strategy for regulating gene expression during differentiation. This study contributes to the identification of relevant proteins involved in the metacyclogenesis process. The identification and molecular characterization of these proteins will render vital information about the steps of the parasite differentiation into the infective form.

Unusual features of poly[dT-dG].[dC-dA] stretches in CDS-flanking regions of Trypanosoma cruzi genome

In trypanosomatids, the mechanisms of gene expression regulation are not yet well understood. The genes are organized into long polycistronic transcription units separated by intergenic regions that may contain the signaling information for nucleic acid processing. Poly-dinucleotides are frequent in these regions and have been proposed to be involved in gene expression regulation. We analyzed their frequency in CDS-flanking sequences of sense strands in Trypanosoma cruzi and established that all but poly[dC-dC], poly[dC-dG], and poly[dG-dG] are significantly more frequent than expected by chance. Poly[dT-dG].[dC-dA] is among the longest and most frequent poly-dinucleotides and shows a remarkable strand asymmetry. Furthermore, electrophoretic mobility shift assays using T. cruzi epimastigotes nuclear extracts demonstrated the existence of at least, one sequence specific single-strand binding activity for each strand. These results strongly suggest that poly[dT-dG].[dC-dA] sequence is involved in regulatory mechanisms of relevance for the parasite biology.

Trypanosoma cruzi: a gene family encoding chitin-binding-like proteins is posttranscriptionally regulated during metacyclogenesis

The development of the representation of differential expression method has lead to the cloning of Trypanosoma cruzi stage-specific genes. We used this method to characterize a multicopy gene family differentially expressed during metacyclogenesis. The genomic and cDNA clones sequenced encoded three short cysteine-rich polypeptides, of two types, with predicted molecular masses of 7.1, 10.4, and 10.8 kDa. We searched GenBank for similar sequences and found that the sequences of these clones were similar to that encoding the wheat germ agglutinin protein. The region of similarity corresponds to the chitin-binding domain, with eight similarly positioned half-cysteines and conserved aromatic residues involved in chitin recognition. Multiple copies of the genes of this family are present on a high- molecular-mass chromosome. We studied the expression of genes of this family during metacyclogenesis by determining messenger RNA (mRNA) levels. The mRNAs for the members of this gene family were present in the total RNA fraction but were mobilized to the polysomal fraction of adhered (differentiating) epimastigotes during metacyclogenesis, with a peak of accumulation at 24 of differentiation. Polyclonal antisera were raised against a recombinant protein and a synthetic peptide. The specific sera obtained detected 7- and 11-kDa proteins in T. cruzi total protein extracts. The 11-kDa protein was present in similar amounts in the various cell populations, whereas the 7-kDa protein displayed differential synthesis during metacyclogenesis, with maximal levels in 24-h-adhered (differentiating) epimastigotes.

Trypanosoma cruzi: molecular cloning of a gene coding for a putative vacuolar protein

We describe the characterization of Tc38, a Trypanosoma cruzi gene coding for a 337-amino-acid protein with a predicted molecular mass of 38 kDa. Tc38 presents similarities to the plant storage vacuolar protein gamma-3-hordein involved in the transport and targeting of prolamins to the vacuole of developing barley endosperm. Western blot analysis using a polyclonal antiserum against recombinant Tc38 revealed that the protein is differentially expressed in the different life stages of the parasite, showing a higher expression in the epimastigote and tripomastigote stages. Immunofluorescence studies suggest that the protein is located in putative vacuolar structures in epimastigotes. The functionality of this protein in T. cruzi remains to be elucidated.

Characterization of a new ATP-binding cassette transporter in Trypanosoma cruzi associated to a L1Tc retrotransposon

We have characterized the tcpgp1-like gene of Trypanosoma cruzi, a new ATP-binding cassette (ABC) transporter. tcpgp1 codes for a 1035 amino acid protein with a considerable homology to LtpgpA of Leishmania. Tcpgp1 lacks the conserved sequences corresponding to the second nucleotide-binding domain of other ABC transporters due to the insertion of the L1Tc non-LTR retrotransposon.

A new member of YER057c family in Trypanosoma cruzi is adjacent to an ABC-transporter

Tcp17 is a Trypanosoma cruzi gene located contiguous to the ABC-transporter tcpgp2. The protein contains 160 amino acid residues with a predicted molecular mass of 16.5kDa. Western blot analysis using a polyclonal antiserum against recombinant TCP17 revealed that the protein is only expressed in the epimastigote form of the parasite; we did not detect the protein either in the amastigote or trypomastigote forms. A sequence comparison of TCP17 showed a remarkable homology with a conserved family of prokaryotic and eukaryotic proteins called YER057c whose function has not yet been characterized. Here, we propose a new signature of this family considering the N-terminal: [IV]-X(4)-[AV]-[AP]-X-[AP]-X(3)-Y-X(9)-[LIVF]-X(2)-[SA]-G-[QS], and the C-terminal: [AT]-R-X(2)-[IVFY]-X-[VC]-X(2)-L-P-X(4)-[LIVM]-E-[IVM] -[DE] motifs. Immunofluorescence and immunoelectron microscopy studies suggest that the protein has a wide distribution in the cell, with a higher concentration in the external side of the plasma membrane, on the Golgi complex and on cytoplasmic vacuoles. Although the physiological function of TCP17 is unknown, its conservation in evolution suggests biological relevance in the parasite.

Molecular characterization of a P-glycoprotein-related tcpgp2 gene in Trypanosoma cruzi

We have cloned, sequenced and characterized a gene from Trypanosoma cruzi (Y strain), termed tcpgp2, which encodes a member of the ABC (ATP-binding cassette) superfamily of evolutionarily conserved transport proteins. The nucleotide sequence of the tcpgp2 gene was determined. It presents a 4602-bp open reading frame, coding for a 1534-amino acid protein, with a predicted molecular mass of 169,470 Da. The deduced amino acid sequence of tcpgp2 exhibited a remarkable homology with the P-glycoprotein-related genes of Leishmania tarentolae, the yeast cadmium factor (YCF1) and the human multidrug resistance-associated protein (MRP). Southern blot analysis using a specific probe indicated that the Tcpgp2 P-glycoprotein is encoded by a single copy gene which maps to a chromosome of about 900 kb. Northern blot analysis revealed that tcpgp2 gene is expressed as a polyadenylated transcript of approximately 5 kb in dividing amastigote and epimastigote forms; we did not detect the transcript in the non-dividing trypomastigote forms of the parasite. Gene transfection experiments in Leishmania tropica indicated that, under the conditions tested, tcpgp2 gene is not involved in drug resistance.

A developmentally regulated gene of Echinococcus granulosus codes for a 15.5-kilodalton polypeptide related to fatty acid binding proteins

A stage-specific expressed gene has been isolated from a cDNA expression library of Echinococcus granulosus protoscolices. The isolated clone contains the complete coding sequence. The corresponding protein (EgDf1) has a molecular weight of 15.5 kDa and is expressed at the tegumental level in the protoscolices, being undetectable in the germinal layer of the metacestode. This protein shares an important homology with a family of low-molecular weight proteins involved in the binding of hydrophobic ligands. This family includes a protein of Schistosoma mansoni (Sm 14) that has immunoprotective activity in rodents. Histochemical and metabolic data already reported for E. granulosus suggest that EgDf1 could be a molecular marker for early events in the process of protoscolex differentiation.