Abstract
Three siblings born to Turkish parents from the same village had normal brain development until acute neurological deterioration between 12 months and 8 years of age. Consequent loss of all acquired motor, social, and language functions following infections was associated with a pontine cyst, calcification, and cerebellar atrophy. Exome sequencing revealed a homozygous c.1297G>A (p.Gly433Ser) alteration in BEND4, which was predicted to be deleterious in in silico analysis tools and segregated in multiple affected individuals in the family. BEND4 has not been associated with any existing disease. Immunofluorescence microscopy analysis of wild-type and mutant BEND4 expressing Vero cells showed nuclear and cytoplasmic localization. Wild-type BEND4 displayed a network-like distribution, whereas mutant BEND4 showed a juxtanuclear distribution pattern. Differential proteome analysis of Vero cells expressing BEND4 revealed that mutant BEND4 expression caused selective increase in reticulocalbin-1 and endoplasmic reticulum resident protein-29. Both proteins are associated with the endoplasmic reticulum and are primarily involved in protein processing and folding pathways. Any defect or stress in protein folding creates stress on cells and may cause chronic damage. This is the first study showing that pathogenic BEND4 variants may lead to an infection-induced acute necrotizing encephalopathy as demonstrated in characteristic neuroimaging findings.