Viruses and viral components have been shown to manipulate the expression of host microRNAs (miRNAs) to their advantage, and in some cases to play essential roles in cancer pathogenesis. Burkitt lymphoma (BL), a highly aggressive B-cell derived cancer, is significantly over-represented among people infected with HIV. This study adds to accumulating evidence demonstrating that the virus plays a direct role in promoting oncogenesis. A custom miRNA PCR was used to identify 32 miRNAs that were differently expressed in Burkitt lymphoma cells exposed to HIV-1, with a majority of these being associated with oncogenic processes. Of those, hsa-miR-200c-3p, a miRNA that plays a crucial role in cancer cell migration, was found to be significantly downregulated in both the array and in single-tube validation assays. Using an in vitro transwell system we found that this downregulation correlated with significantly enhanced migration of BL cells exposed to HIV-1. Furthermore, the expression of the ZEB1 and ZEB2 transcription factors, which are promotors of tumour invasion and metastasis, and which are direct targets of hsa-miR-200c-3p, were found to be enhanced in these cells. This study therefore identifies novel miRNAs as role players in the development of HIV-associated BL, with one of these miRNAs, hsa-miR-200c-3p, being a candidate for further clinical studies as a potential biomarker for prognosis in patients with Burkitt lymphoma, who are HIV positive.

Hearing impairment (HI) is a sensory disorder with a prevalence of 0.0055 live births in South Africa. DNA samples from a South African family presenting with progressive, autosomal dominant non-syndromic HI were subjected to whole-exome sequencing, and a novel monoallelic variant in REST [c.1244GC; p.(C415S)], was identified as the putative causative variant. The co-segregation of the variant was confirmed with Sanger Sequencing. The variant is absent from databases, 103 healthy South African controls, and 52 South African probands with isolated HI. In silico analysis indicates that the p.C415S variant in REST substitutes a conserved cysteine and results in changes to the surrounding secondary structure and the disulphide bonds, culminating in alteration of the tertiary structure of REST. Localization studies using ectopically expressed GFP-tagged Wild type (WT) and mutant REST in HEK-293 cells show that WT REST localizes exclusively to the nucleus; however, the mutant protein localizes throughout the cell. Additionally, mutant REST has an impaired ability to repress its known target AF1q. The data demonstrates that the identified mutation compromises the function of REST and support its implication in HI. This study is the second report, worldwide, to implicate REST in HI and suggests that it should be included in diagnostic HI panels.

Genetic studies and phenotypic expansion of hearing loss (HL) for people living in Africa are greatly needed. We evaluated the clinical phenotypes of three affected siblings presenting non-syndromic (NS) HL and five unaffected members of a consanguineous Ghanaian family. Analysis of exome sequence data was performed for all affected and one unaffected family members. In-depth genetic and cellular characterization studies were performed to investigate biological significance of the implicated variant using bioinformatic tools and cell-based experimentation. Audiological examinations showed severe-to-profound, bilateral, symmetrical, and post-lingual onset. The whole-exome sequencing (WES) identified a homozygous frameshift variant: MARVEL domain containing 2 (MARVELD2):c.1058dup;p.(Val354Serfs*5) in all affected siblings. This frameshift variant leads to an early stop codon insertion and predicted to be targeted by nonsense medicated decay (mutant protein predicted to lack conserved C-terminal domain if translated). Cell immunofluorescence and immunocytochemistry studies exposed the functional impact of the mutant protein’s expression, stability, localization, protein–protein binding, barrier function, and actin cytoskeleton architecture. The identified variant segregates with NSHL in the index Ghanaian family. The data support this nonsense variant as pathogenic, likely to impact the homeostasis of ions, solutes, and other molecules, compromising membrane barrier and signaling in the inner ear spaces.