Chadi Soukkarieh

Role of BMPs in controlling the spatial and temporal origin of GFAP astrocytes in the embryonic spinal cord.

In the vertebrate central nervous system (CNS), astrocytes are the most abundant and functionally diverse glial cell population. However, the mechanisms underlying their specification and differentiation are still poorly understood. In this study, we have defined spatially and temporally the origin of astrocytes and studied the role of BMPs in astrocyte development in the embryonic chick spinal cord. Using explant cultures, we show that astrocyte precursors started migrating out of the neuroepithelium in the mantle layer from E5, and that the dorsal-most level of the neuroepithelium, from the roof plate to the dl3 level, did not generate GFAP-positive astrocytes. Using a variety of early astrocyte markers together with functional analyses, we show that dorsal-most progenitors displayed a potential for astrocyte production but that dorsally-derived BMP signalling, possibly mediated through BMP receptor 1B, promoted neuronal specification instead. BMP treatment completely prevented astrocyte development from intermediate spinal cord explants at E5, whereas it promoted it at E6. Such an abrupt change in the response of this tissue to BMP signalling could be correlated to the onset of new foci of BMP activity and enhanced expression of BMP receptor 1A, suggesting that BMP signalling could promote astrocyte development in this region.

A Simple Method to Isolate and Expand Human Umbilical Cord Derived Mesenchymal Stem Cells: Using Explant Method and Umbilical Cord Blood Serum

Background and Objectives Mesenchymal stem cells (MSCs) are multipotent stem cells that can be isolated from umbilical cords and are therapeutically used because of their ability to differentiate into various types of cells, in addition to their immunosuppressive and anti-inflammatory properties. Fetal bovine serum (FBS), considered as the standard additive when isolating and culturing MSCs, has a major limitation related to its animal origin. Here, we employed a simple and economically efficient protocol to isolate MSCs from human umbilical cord tissues without using digestive enzymes and replacing FBS with umbilical cord blood serum (CBS). Methods and Results MSCs were isolated by culturing umbilical cord pieces in CBS or FBS supplemented media. Expansion and proliferation kinetics of cells isolated by explant method in the presence of either FBS or CBS were measured, with morphology and multi-differentiation potential of expanded cells characterized by flow cytometry, RT-PCR, and immunofluorescence. MSCs maintained morphology, immunophenotyping, multi-differentiation potential, and self-renewal ability, with better proliferation rates for cells cultured in CBS compared to FBS supplement media. Conclusions We here present a simple, reliable and efficient method to isolate MSCs from umbilical cord tissues, where cells maintained proliferation, differentiation potential and immunophenotyping properties and could be efficiently expanded for clinical applications.

Purification of polyclonal IgG specific for Camelid’s antibodies and their recombinant nanobodies

Abstract Camelid’ s heavy-chain antibody (HCAb) consists of only two heavy chains and lacks the two light chains together with the CH1 domain usually found in conventional immunoglobulins. A recombinant single antigen-binding entity, named VHH (or Nanobody®) was generated by reengineering the variable domains from HCAb. This study focuses on the detection of camelid´s immunoglobulins as well as their derivative nanobodies using a universal anti-camel antibody produced in rabbit (rIgG). Starting from a crude rabbit serum, a standard stock of rIgG (1 mg/ml) was prepared after purification by affinity chromatography using protein-A column. As expected, rIgG was able to detect camel antibodies in ELISA and immunoblotting, and its reactivity was equal against all different camel IgG subclasses, which were purified from serum by differential affinity chromatography on protein-G and -A. Interestingly, rIgG also recognized nanobodies since they were originally part of camel HCAbs, providing an alternative method to detect the corpus of these recombinant proteins rather than targeting their artificial tags. These data suggest that the anti-camel rIgG described here could be efficiently applied at different stages of nanobody technology, including the quantitation of the issued nanobodies and their detection when bound to target antigens.

Molecular cloning and expression of the Leishmania tropica KMP-11 gene.

Kinetoplastid membrane protein-11 (KMP-11) is a small protein of 11 kDa present in all kinetoplastid protozoa studded so far. This protein which is highly expressed in all stages of the Leishmania life cycle is considered a potential candidate for a leishmaniasis vaccine against many leishmania species. KMP-11 has been recently described in Leishmania tropica. In the present study, the KMP-11 gene was extracted from L. tropica by PCR using two oligonucleotide primers designed to amplify the entire coding region of this gene. Then, the purified PCR products were successfully ligated into a high expression vector the pRSET-GFP. This expression vector provides the opportunity to clone the desired insert as a fusion protein with a GFP and a tag, polyhistidine region. The GFP use as a carrier to improve immune response and the polyhistidine tag facilitates detection of the expressed protein with anti-His antibodies and also purification of the protein using affinity purification. After wards KMP-11 coding region was sequenced and the recombinant protein was induced and purified from Escherichia coli cultures. The results of the present study will increase our knowledge about molecular cloning and expression of the L. tropica KMP-11 gene, and this may be used as an effective target for controlling cutenous leishmaniasis.

First genotyping of Cryptosporidium spp. in pre-weaned calves, broiler chickens and children in Syria by PCR-RFLP analysis.

In this study, PCR-RFLP was used for the first time in Syria for genotyping Cryptosporidium species of man, calves and chickens. The total of 391 fecal samples included 213 from children with diarrhea (<5years), 67 from pre-weaned calves with diarrhea and 111 from broiler chicken farms. All samples were collected and examined with acid fast stain to detect the positive samples. Subsequently a nested-PCR test was performed on 35 positive samples (17 from calves, 11 from chicken, and 7 from children) targeting SSU rRNA gene, and was followed by RFLP analysis using three restriction enzymes SspI, VspI and MboII. Results showed that C. parvum was the only identified species in children and calves, on the other hand C. baileyi was identified in broilers in addition to another species with unknown RFLP profile in comparison to those which have been described in chicken. Further studies using more genes are needed to sequence and detect subtypes of this parasite.

Cloning, expression, purification and characterization of Leishmania tropica PDI-2 protein

Abstract In Leishmania species, protein disulfide isomerase (PDI) is an essential enzyme that catalyzes thiol-disulfide interchange. The present work describes the isolation, cloning, sequencing and expression of the pdI-2 gene. Initially, the gene was amplified from L. tropica genomic DNA by PCR using specific primers before cloning into the expression vector pET-15b. The construct pET/pdI-2 was transformed into BL21(DE3) cells and induced for the protein expression. SDS-PAGE and western blot analysis showed that the expressed protein is about 51 kDa. Cloned gene sequence analysis revealed that the deduced amino acid sequence showed significant homology with those of several parasites PDIs. Finally, recombinant protein was purified with a metal-chelating affinity column. The putative protein was confirmed as a thiol - disulfide oxidoreductase by detecting its activity in an oxidoreductase assay. Assay result of assay suggested that the PDI-2 protein is required for both oxidation and reduction of disulfide bonds in vitro. Antibodies reactive with this 51 kDa protein were detected by Western blot analysis in sera from human infected with L. tropica. This work describes for the first time the enzymatic activity of recombinant L. tropica PDI-2 protein and suggests a role for this protein as an antigen for the detection of leishmaniasis infection.

Onset of Spinal Cord Astrocyte Precursor Emigration from the Ventricular Zone Involves the Zeb1 Transcription Factor

During spinal cord development, astrocyte precursors arise from neuroepithelial progenitors, delaminate from the ventricular zone, and migrate toward their final locations where they differentiate. Although the mechanisms underlying their early specification and late differentiation are being deciphered, less is known about the temporal control of their migration. Here, we show that the epithelial-mesenchymal transition regulator Zeb1 is expressed in glial precursors and report that loss of Zeb1 function specifically delays the onset of astrocyte precursor delamination from the ventricular zone, correlating with transient deregulation of the adhesion protein Cadherin-1. Consequently, astrocyte precursor invasion into the Zeb1-/- mutant white matter is delayed, and induction of their differentiation is postponed. These findings illustrate how fine regulation of adhesive properties influences the onset of neural precursor migration and further support the notion that duration of exposure of migrating astrocyte precursors to environmental cues and/or their correct positioning influence the timing of their differentiation.