title: Clinical and cellular features in patients with primary autosomal recessive microcephaly and a novel CDK5RAP2 mutation.
abstract: BACKGROUND
  Primary autosomal recessive microcephaly (MCPH) is a rare neurodevelopmental disorder that results in severe microcephaly at birth with pronounced reduction in brain volume, particularly of the neocortex, simplified cortical gyration and intellectual disability. Homozygous mutations in the Cyclin-dependent kinase 5 regulatory subunit-associated protein 2 gene CDK5RAP2 are the cause of MCPH3. Despite considerable interest in MCPH as a model disorder for brain development, the underlying pathomechanism has not been definitively established and only four pedigrees with three CDK5RAP2 mutations have been reported. Specifically for MCPH3, no detailed radiological or histological descriptions exist.
  
  
  RESULTS
  We sought to characterize the clinical and radiological features and pathological cellular processes that contribute to the human MCPH3 phenotype. Haplotype analysis using microsatellite markers around the MCPH1-7 and PNKP loci in an Italian family with two sons with primary microcephaly, revealed possible linkage to the MCPH3 locus. Sequencing of the coding exons and exon/intron splice junctions of the CDK5RAP2 gene identified homozygosity for the novel nonsense mutation, c.4441C > T (p.Arg1481*), in both affected sons. cMRI showed microcephaly, simplified gyral pattern and hypogenesis of the corpus callosum. The cellular phenotype was assessed in EBV-transformed lymphocyte cell lines established from the two affected sons and compared with healthy male controls. CDK5RAP2 protein levels were below detection level in immortalized lymphocytes from the patients. Moreover, mitotic spindle defects and disrupted γ-tubulin localization to the centrosome were apparent.
  
  
  CONCLUSIONS
  These results suggest that spindle defects and a disruption of centrosome integrity play an important role in the development of microcephaly in MCPH3.
authors.affiliation: Institute of Cell Biology and Neurobiology, Charité University Medicine, Berlin, Germany.
authors.forename: Lina
authors.initials: L
authors.lastname: Issa
authors.forename: Katrin
authors.initials: K
authors.lastname: Mueller
authors.forename: Katja
authors.initials: K
authors.lastname: Seufert
authors.forename: Nadine
authors.initials: N
authors.lastname: Kraemer
authors.forename: Henning
authors.initials: H
authors.lastname: Rosenkotter
authors.forename: Olaf
authors.initials: O
authors.lastname: Ninnemann
authors.forename: Michael
authors.initials: M
authors.lastname: Buob
authors.forename: Angela M
authors.initials: AM
authors.lastname: Kaindl
authors.forename: Deborah J
authors.initials: DJ
authors.lastname: Morris-Rosendahl
mesh_terms: D015153:Blotting, Western; D018797:Cell Cycle Proteins; D002461:Cell Line, Transformed; D005091:Exons; D005260:Female; D005808:Genes, Recessive; D006239:Haplotypes; D006720:Homozygote; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics*; D007438:Introns; D008279:Magnetic Resonance Imaging; D008297:Male; D008831:Microcephaly / Q000235:genetics* / Q000473:pathology; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics*; D010375:Pedigree; D010641:Phenotype; D016133:Polymerase Chain Reaction
chemical_list: C405929:CDK5RAP2 protein, human; D018797:Cell Cycle Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins