This study was supported by the Universidad del Rosario and Colciencias (Grants CS/CIGGUR-ABN062-2016 and 672-2014). Colciencias supported Liliana Catherine Patiño´s work (Fellowship: 617, 2013). The authors declare no conflict of interest.
BackgroundRhoptries are specialized organelles from parasites belonging to the phylum Apicomplexa; they secrete their protein content during invasion of host target cells and are sorted into discrete subcompartments within rhoptry neck or bulb. This distribution is associated with these proteins' role in tight junction (TJ) and parasitophorous vacuole (PV) formation, respectively.MethodsPlasmodium falciparum RON2 amino acid sequence was used as bait for screening the codifying gene for the homologous protein in the Plasmodium vivax genome. Gene synteny, as well as identity and similarity values, were determined for ron2 and its flanking genes among P. falciparum, P. vivax and other malarial parasite genomes available at PlasmoDB and Sanger Institute databases. Pvron2 gene transcription was determined by RT-PCR of cDNA obtained from the P. vivax VCG-1 strain. Protein expression and localization were assessed by Western blot and immunofluorescence using polyclonal anti-PvRON2 antibodies. Co-localization was confirmed using antibodies directed towards specific microneme and rhoptry neck proteins.Results and discussionThe first P. vivax rhoptry neck protein (named here PvRON2) has been identified in this study. PvRON2 is a 2,204 residue-long protein encoded by a single 6,615 bp exon containing a hydrophobic signal sequence towards the amino-terminus, a transmembrane domain towards the carboxy-terminus and two coiled coil α-helical motifs; these are characteristic features of several previously described vaccine candidates against malaria. This protein also contains two tandem repeats within the interspecies variable sequence possibly involved in evading a host's immune system. PvRON2 is expressed in late schizonts and localized in rhoptry necks similar to what has been reported for PfRON2, which suggests its participation during target cell invasion.ConclusionsThe identification and partial characterization of the first P. vivax rhoptry neck protein are described in the present study. This protein is homologous to PfRON2 which has previously been shown to be associated with PfAMA-1, suggesting a similar role for PvRON2.
Premature ovarian insufficiency (POI) is a frequent pathology that affects women under 40 years of age, characterized by an early cessation of menses and high FSH levels. Despite recent progresses in molecular diagnosis, the etiology of POI remains idiopathic in most cases. Whole-exome sequencing of members of a Colombian family affected by POI allowed us to identify a novel homozygous donor splice-site mutation in the meiotic gene MSH4 (MutS Homolog 4). The variant followed a strict mendelian segregation within the family and was absent in a cohort of 135 women over 50 years of age without history of infertility, from the same geographical region as the affected family. Exon trapping experiments showed that the splice-site mutation induced skipping of exon 17. At the protein level, the mutation p.Ile743_Lys785del is predicted to lead to the ablation of the highly conserved Walker B motif of the ATP-binding domain, thus inactivating MSH4. Our study describes the first MSH4 mutation associated with POI and increases the number of meiotic/DNA repair genes formally implicated as being responsible for this condition.
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