title: Truncation of the E3 ubiquitin ligase component FBXO31 causes non-syndromic autosomal recessive intellectual disability in a Pakistani family.
abstract: In this study, we have performed autozygosity mapping on a large consanguineous Pakistani family segregating with intellectual disability. We identified two large regions of homozygosity-by-descent (HBD) on 16q12.2-q21 and 16q24.1-q24.3. Whole exome sequencing (WES) was performed on an affected individual from the family, but initially, no obvious mutation was detected. However, three genes within the HBD regions that were not fully captured during the WES were Sanger sequenced and we identified a five base pair deletion (actually six base pairs deleted plus one base pair inserted) in exon 7 of the gene FBXO31. The variant segregated completely in the family, in recessive fashion giving a LOD score of 3.95. This variant leads to a frameshift and a premature stop codon and truncation of the FBXO31 protein, p.(Cys283Asnfs*81). Quantification of mRNA and protein expression suggests that nonsense-mediated mRNA decay also contributes to the loss of FBXO31 protein in affected individuals. FBXO31 functions as a centrosomal E3 ubiquitin ligase, in association with SKP1 and Cullin-1, involved in ubiquitination of proteins targeted for degradation. The FBXO31/SKP1/Cullin1 complex is important for neuronal morphogenesis and axonal identity. FBXO31 also plays a role in dendrite growth and neuronal migration in developing cerebellar cortex. Our finding adds further evidence of the involvement of disruption of the protein ubiquitination pathway in intellectual disability.
authors.affiliation: Human Molecular Genetics Lab, Department of Bioinformatics and Biotechnology, FBAS, International Islamic University, Islamabad, Pakistan.
authors.forename: Asif
authors.initials: A
authors.lastname: Mir
authors.forename: Kumudesh
authors.initials: K
authors.lastname: Sritharan
authors.forename: Kirti
authors.initials: K
authors.lastname: Mittal
authors.forename: Nasim
authors.initials: N
authors.lastname: Vasli
authors.forename: Carolina
authors.initials: C
authors.lastname: Araujo
authors.forename: Talal
authors.initials: T
authors.lastname: Jamil
authors.forename: Muhammad Arshad
authors.initials: MA
authors.lastname: Rafiq
authors.forename: Zubair
authors.initials: Z
authors.lastname: Anwar
authors.forename: Anna
authors.initials: A
authors.lastname: Mikhailov
authors.forename: Sobiah
authors.initials: S
authors.lastname: Rauf
authors.forename: Huda
authors.initials: H
authors.lastname: Mahmood
authors.forename: Abdul
authors.initials: A
authors.lastname: Shakoor
authors.forename: Sabir
authors.initials: S
authors.lastname: Ali
authors.forename: Joyce
authors.initials: J
authors.lastname: So
authors.forename: Farooq
authors.initials: F
authors.lastname: Naeem
authors.forename: Muhammad
authors.initials: M
authors.lastname: Ayub
authors.forename: John B
authors.initials: JB
authors.lastname: Vincent
mesh_terms: D015153:Blotting, Western; D002874:Chromosome Mapping; D002885:Chromosomes, Human, Pair 16 / Q000235:genetics*; D003241:Consanguinity; D044783:F-Box Proteins / Q000235:genetics*; D005260:Female; D016368:Frameshift Mutation / Q000235:genetics; D005808:Genes, Recessive; D006720:Homozygote; D006801:Humans; D007124:Immunoenzyme Techniques; D008607:Intellectual Disability / Q000235:genetics* / Q000473:pathology; D008297:Male; D010154:Pakistan; D010375:Pedigree; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017384:Sequence Deletion; D025521:Tumor Suppressor Proteins / Q000235:genetics*
chemical_list: D044783:F-Box Proteins; C507917:FBXO31 protein, human; D012333:RNA, Messenger; D025521:Tumor Suppressor Proteins