Genetic analysis of the mouse brain proteome

Proteome analysis is a fundamental step in systematic functional genomics. Here we have resolved 8,767 proteins from the mouse brain proteome by large-gel two-dimensional electrophoresis. We detected 1,324 polymorphic proteins from the European collaborative interspecific backcross. Of these, we mapped 665 proteins genetically and identified 466 proteins by mass spectrometry. Qualitatively polymorphic proteins, to 96%, reflect changes in conformation and/or mass. Quantitatively polymorphic proteins show a high frequency (73%) of allele-specific transmission in codominant heterozygotes. Variations in protein isoforms and protein quantity often mapped to chromosomal positions different from that of the structural gene, indicating that single proteins may act as polygenic traits. Genetic analysis of proteomes may detect the types of polymorphism that are most relevant in disease-association studies.     

Mutations in the gene encoding the lamin B receptor produce an altered nuclear morphology in granulocytes (Pelger-Huët anomaly)

Pelger-Hu?t anomaly (PHA; OMIM *169400) is an autosomal dominant disorder characterized by abnormal nuclear shape and chromatin organization in blood granulocytes. Affected individuals show hypolobulated neutrophil nuclei with coarse chromatin. Presumed homozygous individuals have ovoid neutrophil nuclei, as well as varying degrees of developmental delay, epilepsy and skeletal abnormalities. Homozygous offspring in an extinct rabbit lineage showed severe chondrodystrophy, developmental anomalies and increased pre- and postnatal mortality. Here we show, by carrying out a genome-wide linkage scan, that PHA is linked to chromosome 1q41-43. We identified four splice-site, two frameshift and two nonsense mutations in LBR, encoding the lamin B receptor. The lamin B receptor (LBR), a member of the sterol reductase family, is evolutionarily conserved and integral to the inner nuclear membrane; it targets heterochromatin and lamins to the nuclear membrane. Lymphoblastoid cells from heterozygous individuals affected with PHA show reduced expression of the lamin B receptor, and cells homozygous with respect to PHA contain only trace amounts of it. We found that expression of the lamin B receptor affects neutrophil nuclear shape and chromatin distribution in a dose-dependent manner. Our findings have implications for understanding nuclear envelope-heterochromatin interactions, the pathogenesis of Pelger-like conditions in leukemia, infection and toxic drug reactions, and the evolution of neutrophil nuclear shape.     

Familial association in serum IgE levels

Summary The serum IgE levels measured by RIST correlated closely with those obtained by the single radioimmunodiffusion method. Values for husband and wife were closely related as were those between father and daughter but in contrast to previous observations no significant relationship existed between IgE levels for mother and son.Acknowledgments. The Busselton population studies, of which this paper forms part, have been supported by the University of Western Australia the Arnold Yeldham and Mary Raine Foundation, the National Heart Foundation of Australia, Royal Perth Hospital, State Health Laboratories (Western Australia), the National Health and Medical Research Council, Princess Margaret Children's Medical Research Foundation, various private donors, numerous volunteer workers, and the people of Busselton. The authors wish to personally acknowledge support from the Arnold Yeldham and Mary Raine Foundation, the National Health and Medical Research Council and the Asthma Foundation of Western Australia. We are indebted to Drs.K. J. Cullen andR. C. Godfrey for making available valuable material from the Busselton population survey.     

Membrane protein sequestering by ionic protein-lipid interactions

Neuronal exocytosis is catalysed by the SNAP receptor protein syntaxin-1A, which is clustered in the plasma membrane at sites where synaptic vesicles undergo exocytosis. However, how syntaxin-1A is sequestered is unknown. Here we show that syntaxin clustering is mediated by electrostatic interactions with the strongly anionic lipid phosphatidylinositol-4,5-bisphosphate (PIP2). Using super-resolution stimulated-emission depletion microscopy on the plasma membranes of PC12 cells, we found that PIP2 is the dominant inner-leaflet lipid in microdomains about 73 nanometres in size. This high accumulation of PIP2 was required for syntaxin-1A sequestering, as destruction of PIP2 by the phosphatase synaptojanin-1 reduced syntaxin-1A clustering. Furthermore, co-reconstitution of PIP2 and the carboxy-terminal part of syntaxin-1A in artificial giant unilamellar vesicles resulted in segregation of PIP2 and syntaxin-1A into distinct domains even when cholesterol was absent. Our results demonstrate that electrostatic protein-lipid interactions can result in the formation of microdomains independently of cholesterol or lipid phases.