Comparison of in vitro transformation efficiency methods for Plasmodium falciparum

Poor efficiency plagues conventional methods to transfect Plasmodium falciparum with genetic modifications, impeding research aimed at limiting the damage wrought by this agent of severe malaria. Here, we sought and documented improvements, using fluoresce imaging, cell sorting, and drug selection as means to measure efficiency. Through the transfection of EGFP plasmid, the transfection efficiency of the three methods used in this study was as high as 10^-3. A method that pre-loaded uninfected erythrocytes with plasmids using the Bio-Rad Gene Pulser Xcell achieved the highest efficiency (0.48%±0.06%), twice the efficiency of a method using nuclear transfection of ring stages employing the 4D-Nucleofector^TM X Kit L. We also evaluated an approach using the Nucleofactor system to transform schizont stages. We considered efficiency and the time required to complete drug screening experiments when evaluating transfection methods. Fluorescence measurements confirmed greater efficiencies for the Pre-load method (52.4% vs. 25%; P < 0.0001), but the Nuc-Ring method required less time to complete drug selection experiments following CRISPR/Cas9 editing. These data should benefit future studies seeking to remove or modify genes of P. falciparum.

Apoptosis and its pathway in X gene-transfected HepG2 cells

AIM: To investigate the effect of hepatitis B virus (HBV) X gene on apoptosis and expressions of apoptosis factors in X gene-transfected HepG₂ cells.

METHODS: The HBV X gene eukaryon expression vector pcDNA3-X was transiently transfected into HepG₂ cells by lipid-media transfection. Untransfected HepG₂ and HepG₂ transfected with pcDNA3 were used as controls. Expression of HBx in HepG₂ was identified by RT-PCR. MTT and TUNEL were employed to measure proliferation and apoptosis of cells in three groups. Semi-quantified RT-PCR was used to evaluate the expression levels of Fas/FasL, Bax/Bcl-xL, and c-myc in each group.

RESULTS: HBV X gene was transfected into HepG₂ cells successfully. RT-PCR showed that HBx was only expressed in HepG₂/pcDNA3-X cells, but not expressed in HepG₂ and HepG₂/pcDNA3 cells. Analyzed by MTT, cell proliferation capacity was obviously lower in HepG₂/pcDNA3-X cells (0.08910±0.003164) than in HepG₂ (0.14410±0.004927) and HepG₂/pcDNA3 cells (0.12150±0.007159) (P<0.05 and P<0.01). Analyzed by TUNEL, cell apoptosis was much more in HepG₂/pcDNA3-X cells (980/2 000) than HepG₂ (420/2 000), HepG₂/pcDNA3 cells (520/2 000) (P<0.05 and P<0.01). Evaluated by semi-quantified RT-PCR, the expression level of Fas/FasL was significantly higher in HepG₂ cells transfected with HBx than in HepG₂ and HepG₂/pcDNA3cells (P<0.05 and P<0.01). Bax/Bcl-xL expression level was also elevated in HepG₂/pcDNA3-X cells (P<0.05 and P<0.01). Expression of c-myc was markedly higher in HepG₂/pcDNA3-X cells than in HepG₂ and HepG₂/pcDNA3 cells (P<0.05 andP<0.01).

CONCLUSION: HBV X gene can impair cell proliferation capacity, improve cell apoptosis, and upregulate expression of apoptosis factors. The intervention of HBV X gene on the expression of apoptosis factors may be a possible mechanism responsible for the change in cell apoptosis and proliferation.