De novo mutations in FBRSL1 cause a novel recognizable malformation and intellectual disability syndrome

We report truncating de novo variants in specific exons ofFBRSL1 in three unrelated children with an overlapping syndromic phenotype with respiratory insufficiency, postnatal growth restriction, microcephaly, global developmental delay and other malformations. The function ofFBRSL1 is largely unknown. Interestingly, mutations in theFBRSL1 paralogueAUTS2 lead to an intellectual disability syndrome (AUTS2 syndrome). We determined humanFBRSL1 transcripts and describe protein-coding forms by Western blot analysis as well as the cellular localization by immunocytochemistry stainings. All detected mutations affect the two short N-terminal isoforms, which show a ubiquitous expression in fetal tissues. Next, we performed a Fbrsl1 knockdown inXenopus laevis embryos to explore the role of Fbrsl1 during development and detected craniofacial abnormalities and a disturbance in neurite outgrowth. The aberrant phenotype inXenopus laevis embryos could be rescued with a human N-terminal isoform, while the long isoform and the N-terminal isoform containing the mutation p.Gln163* isolated from a patient could not rescue the craniofacial defects caused by Fbrsl1 depletion. Based on these data, we propose that the disruption of the validated N-terminal isoforms of FBRSL1 at critical timepoints during embryogenesis leads to a hitherto undescribed complex neurodevelopmental syndrome.
Source: Human Genetics - Category: Genetics & Stem Cells Source Type: research