Updated project metadata. Marinesco-Sjögren syndrome (MSS) is a neurodegenerative disorder caused by autosomal recessive SIL1 mutations. SIL1 acts as a nucleotide exchange factor for the endoplasmic reticulum (ER) resident chaperone BiP. As BiP controls many ER-related processes, it is likely to contribute to MSS pathology. Owing to the absence of appropriate in vitro models, the precise pathophysiological mechanisms leading to neurodegeneration in MSS are still elusive. Here, we demonstrate for the first time that SIL1-depleted HEK293 cells can be used to reveal these mechanisms using ultra-structural, cell biological, and biochemical approaches.