A novel biallelic frameshift variant in C2orf69 causing developmental regression, seizures, microcephaly, autistic features, and hypertonia.

Combined oxidative phosphorylation deficiency type 53 (COXPD53) is an autosomal recessive neurodevelopmental disorder (NDD) caused by homozygous variants in the gene C2orf69. Here, we report a novel frameshift variant c.187_191dupGCCGA, p.D64Efs*56 identified in an individual with clinical presentation of COXPD53 with developmental regression and autistic features. The variant c.187_191dupGCCGA, p.D64Efs*56 represents the most N-terminal part of C2orf69. Notable clinical features of COXPD53of the proband include developmental delay, developmental regression, seizures, microcephaly, and hypertonia. Structural brain defects of cerebral atrophy, cerebellar atrophy, hypomyelination, and thin corpus callosum were also observed. While we observe strong phenotypic overlap among affected individuals with C2orf69 variants, developmental regression and autistic features have not been previously described in individuals with COXPD53. Together, this case expands the genetic and clinical phenotypic spectrum of C2orf69-associated COXPD53.

Hydrogen peroxide-induced oxidative stress and its impact on innate immune responses in lung carcinoma A549 cells.

The immune responses, involved in recognition of cancer-specific antigens, are of particular interest as this may provide major leads towards developing new vaccines and antibody therapies against cancer. An effective treatment for cancer is still a challenge because there are many mechanisms through which the tumor cells can escape the host immune surveillance. Oxidative stress or respiratory burst which is host's mechanism to kill the foreign particles is used as defense mechanism by the tumor cells. The tumor cells uses this oxidative stress to form neo-antigens which in turn makes them undetectable and can escape the host immune surveillance. The human lung carcinoma (A549) cells were treated using 100 µM H2O2 to induce oxidative stress, and the extent oxidative modifications were detected at the level of membrane and proteins in form of lipid peroxidation and protein carbonyls respectively. Nitric oxide and iNOS levels were estimated by Griess assay and immunostaining, respectively. The oxidized tumor proteins were visualized on one-dimensional SDS-PAGE. The H2O2-treated (15 min and 24 h post-treatment) A549 cells were co-cultured with THP-1 cells to subsequently visualize the phagocytic activity by Giemsa and CFSE staining to understand the role of neo (oxidized) tumor antigens in eliciting alteration in immune responses. A significant decline in the percent engulfed cells and decrease in the levels of reactive oxygen species was observed. Immunohistostaining for p47phox, which is an important indicator of the oxygen-dependent phagocytosis, showed a decrease in its levels when cells were treated for only 15 min with 100 µM H2O2, whereas at 24-h post-treatment there was no change in the p47phox levels. The study has established oxidative stress as a new pathogenic mechanism of carcinogenesis and will open new avenues for clinical intervention, adjunct therapies for cancer, and its control at the initial stage by targeting these neo-antigens.