LIS1 Missense Mutations

Abstract

Mutations in one allele of the human LIS1 gene cause a severe brain malformation, lissencephaly. Although most LIS1 mutations involve deletions, several point mutations with a single amino acid alteration were described. Patients carrying these mutations reveal variable phenotypic manifestations. We have analyzed the functional importance of these point mutations by examining protein stability, folding, intracellular localization, and protein-protein interactions. Our data suggest that the mutated proteins were affected at different levels, and no single assay could be used to predict the lissencephaly phenotype. Most interesting are those mutant proteins that retain partial folding and interactions. In the case of LIS1 mutated in F31S, the cellular phenotype may be modified by overexpression of specific interacting proteins. Overexpression of the PAF-AH ␣1 subunit dissolved aggregates induced by this mutant protein and increased its half-life. Overexpression of NudE or NudEL localized this mutant protein to spindle poles and kinetochores but had no effect on protein stability. Our results implicate that there are probably different biochemical and cellular mechanisms obstructed in each patient yielding the varied lissencephaly phenotypes.

The phospholipase complex PAFAH Ib regulates the functional organization of the Golgi complex

“…S1 A; unpublished data). A similar distribution was seen by Caspi et al (2003) in cells expressing GFP-α1. Catalytically inactive α1 S47A and α2 S48A, as well as α1 E38D and α2 E39D, were similarly localized (Fig.…”

Lis1 and doublecortin function with dynein to mediate coupling of the nucleus to the centrosome in neuronal migration

“…Intragenic LIS1 or DCX mutations in patients with lissencephaly include missense amino acid changes and truncations ( Cardoso et al, 2000 , 2002 ; Gleeson et al, 2000 ). The mutant proteins are either incorrectly folded ( Sapir et al, 1999 ; Caspi et al, 2003 ) and fail to associate with binding partners ( Feng et al, 2000 ) or fail to bind MTs ( Taylor et al, 2000 ), but no data exist on the effect of these mutations on migration. To assess the function of the mutant proteins quantitatively, patient-related mutant Dcx (R89G, T203R, 303stop; Gleeson et al, 1998 ) or Lis1 (H149R, S169R, D317H; Lo Nigro et al, 1997 ; Pilz et al, 1999 ) was overexpressed.…”

“…This is the first demonstration of a system that can be used to test the effect of patient mutations on neuronal migration. Previous reports have demonstrated that Lis1 with introduced patient mutations is either unstable ( Sapir et al, 1999 ), displays abnormal folding ( Caspi et al, 2003 ), or cannot properly bind to ligands such as mNudE ( Feng et al, 2000 ). Dcx with introduced patient mutations leads to impaired MT polymerizing ability ( Sapir et al, 2000 ; Taylor et al, 2000 ) or cannot bind to the FIGQY-phosphotyrosine motif in neurofascin ( Kizhatil et al, 2002 ).…”

Abnormal centrosome and spindle morphology in a patient with autosomal recessive primary microcephaly type 2 due to compound heterozygous WDR62 gene mutation

“…A central molecular mechanism for microcephaly in MCPH2 may be a deficiency or dysfunction of WDR62 at the spindle pole of dividing cells due to processes such as non-expression, loss of essential spindle targeting domains, misfolding or rapid degradation of the mutant protein [39]. For WDR62 it has been recently demonstrated that siRNA downregulation in murine neural progenitors through in utero electroporation induces early cell cycle exit and a reduced proliferative capacity.…”