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Hum Genet November 1, 2020; 139 (11): 1363-1379.
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De novo mutations in FBRSL1 cause a novel recognizable malformation and intellectual disability syndrome.

Ufartes R , Berger H , Till K , Salinas G , Sturm M , Altmüller J , Nürnberg P , Thiele H , Funke R , Apeshiotis N , Langen H , Wollnik B , Borchers A , Pauli S .

We report truncating de novo variants in specific exons of FBRSL1 in three unrelated children with an overlapping syndromic phenotype with respiratory insufficiency, postnatal growth restriction, microcephaly, global developmental delay and other malformations. The function of FBRSL1 is largely unknown. Interestingly, mutations in the FBRSL1 paralogue AUTS2 lead to an intellectual disability syndrome (AUTS2 syndrome). We determined human FBRSL1 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 in Xenopus laevis embryos to explore the role of Fbrsl1 during development and detected craniofacial abnormalities and a disturbance in neurite outgrowth. The aberrant phenotype in Xenopus 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.

PubMed ID: 32424618
PMC ID: PMC7519918
Article link: Hum Genet
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: auts2 fbrsl1 ncam1
GO keywords: neuron migration
Morpholinos: fbrsl1 MO1

Disease Ontology terms: syndromic intellectual disability
Phenotypes: Xla Wt + fbrsl1 MO (Fig 5. C r3) [+]

Article Images: [+] show captions
References [+] :
Aiken, Tubulin mutations in brain development disorders: Why haploinsufficiency does not explain TUBA1A tubulinopathies. 2020, Pubmed