NDUFA4 Mutations Underlie Dysfunction of a Cytochrome c Oxidase Subunit Linked to Human Neurological Disease

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Mutations in the gene PRRT2 cause paroxysmal kinesigenic dyskinesia with infantile convulsions

Paroxysmal Kinesigenic Dyskinesia with Infantile Convulsions (PKD/IC) is an episodic movement disorder with autosomal dominant inheritance and high penetrance, but the causative gene is unknown. We have now identified four truncating mutations involving the PRRT2 gene in the vast majority (24/25) of well characterized families with PKD/IC. PRRT2 truncating mutations were also detected in 28 of 78 additional families. The PRRT2 gene encodes a proline-rich transmembrane protein of unknown function that has been reported to interact with the t-SNARE, SNAP25. PRRT2 localizes to axons but not to dendritic processes in primary neuronal culture and mutants associated with PKD/IC lead to dramatically reduced PRRT2 protein levels leading ultimately to neuronal hyperexcitability that manifests in vivo as PKD/IC.     

Definition of new alloantigens encoded by genes in the Ly-6 complex

Three alloantigens encoded by Ly-6-linked genes are defined by monoclonal antibodies. The Ly-27.2 antigen is defined by antibody 5075-19.1, Ly-28.2 by 5075-3.6, -12.1, -16.10 and by 5095-16.6. The strain distribution pattern of these antibodies is the same and identical with Ly-6.2. However the tissue distribution of these antigens is unique and distinguishes these antigens from the Ly-6.2 antigen or any known antigen encoded by Ly-6-linked genes. Ly-27.2 is present on all thymocytes, T cells, and B cells but is absent from bone marrow cells, whereas Ly-28.2 is absent from most thymocytes and is present on a subpopulation of T cells and B cells but is found on 60–70% of bone marrow cells. No recombination between the Ly-6/Ly-27/Ly-28 loci was found in linkage studies using 41 recombinant inbred strains and 57 backcross mice and indicates very close linkage of these genes. In addition, close linkage to 24 minor histocompatibility genes was excluded using the Bailey HW bilineal congenic mice. The data presented indicate that either the Ly-6 complex is composed of a family of tightly linked genes or the antigens are the products of a single gene that undergoes extensive modification during differentiation.     

N-glycosylation of HIV-gp120 may constrain recognition by T lymphocytes.

The HIV envelope protein gp120 is heavily glycosylated, having 55% of its molecular mass contributed by N-linked carbohydrates. We investigated the role of N-glycosylation in presentation of HIV-gp120 to T cells. T cell clones obtained from humans immunized with a recombinant nonglycosylated form of HIV-gp120 (env 2-3) were studied for their ability to recognize both env 2-3 and glycosylated gp120. We found that 20% of CD4+ T cell clones specific for env 2-3 fail to respond to glycosylated gp120 of the same HIV isolate. Using synthetic peptides, we mapped one of the epitopes recognized by such clones to the sequence 292-300 (NESVAINCT), which contains two asparagines that are glycosylated in the native gp120. These findings suggest that N-linked carbohydrates within an epitope can function as hindering structures that limit Ag recognition by T lymphocytes.     

In vitro and in vivo activation of murine gamma/delta T cells induces the expression of IgA, IgM, and IgG Fc receptors.

The present studies examined resting and activated murine gamma/delta T lymphocytes, in vitro and in vivo, for surface expression of FcR. Polyclonal gamma/delta TCR+ lymphocytes selectively grown from the spleen and intestine of normal mice did not express FcR when the cells were in a resting state, but when cells were activated with anti-CD3 antibody virtually all of the splenic gamma/delta lymphocytes and a large subpopulation of the intestinal gamma/delta lymphocytes expressed IgA and IgM FcR. This was confirmed by using transgenic mice. Resting gamma/delta TCR+ lymphocytes from the spleen, thymus, lymph node, and blood of gamma/delta TCR transgenic mice did not express FcR for any of the five major classes of Ig H chains. Activation of the gamma/delta TCR+ cells via the CD3/TCR complex induced high levels of IgM and IgA FcR and low levels of IgG FcR. Finally, in hepatic granulomas of schistosome-infected mice, activated gamma/delta TCR+ cells are present and express high levels of IgA and IgM FcR and low levels of IgG FcR. These investigations establish that transition of gamma/delta TCR+ lymphocytes from a resting to an activated state (triggered via the T3Ti TCR complex) is accompanied by the induction of surface membrane receptors specific for Ig H chain isotypes. The activation-linked expression of FcR on gamma/delta TCR+ lymphocytes provides potential mechanisms for coupling the functional activities of gamma/delta T lymphocytes with immune mechanisms that involve Ig molecules, such as antibody-dependent cellular cytotoxicity.     

PRRT2 Regulates Synaptic Fusion by Directly Modulating SNARE Complex Assembly

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Captive breeding, paternity determination, and genetic variation in chimpanzees (Pan troglodytes) in the Australasian region

DNA “fingerprinting” using polymorphic (CA)-repeat microsatellite markers was used to quantify the level of genetic variation present in chimpanzees (Pan troglodytes) in the Australasian region. These markers were also used to determine the paternity of chimpanzees born at Taronga Zoo over a 20-year period. The results suggested that the dominant male in the colony was responsible for siring most, but not all, of the offspring. Where the dominant male was excluded from paternity, the sire was identifiable if all candidate males were available for typing. This enabled us to prove the captive origin of offspring born in the colony during this period. Thus, microsatellite analysis was a useful tool for assignment of familial relationships and improving genetic management of breeding colonies.     

Signal transduction through class I MHC by a monoclonal antibody that detects multiple murine and human class I molecules.

We have generated a hamster anti-mouse class I reactive mAb that is capable of activating T cells in the presence of the cofactor PMA, as assayed by both IFN-gamma production and cellular proliferation. This mAb detects an epitope present on the majority of murine class I molecules, with the known exceptions of H-2Kk and H-2Kq, and is therefore not beta 2-microglobulin-specific. It also recognizes multiple human class I molecules. The epitope recognized by this antibody maps to the class I alpha 1 domain. The activation properties of this mAb are not mediated exclusively through the glycosylphosphatidylinositol-linked Qa-2 molecule, as the antibody activates spleen cells from Qa-2 negative strains. Although class I molecules are not usually considered as activation Ag, these data demonstrate their potential for involvement in signal transduction.     

Low Phylogeographic Structure in a Wide Spread Endangered Australian Frog <Emphasis Type="Italic">Litoria aurea</Emphasis> (Anura: Hylidae)

The green and golden bell frog (Litoria aurea) has a widespread distribution along the south-east coast of Australia. The species range, however, is highly fragmented and remaining populations are predominately isolated and restricted to the coastline. Previously, the range extended further inland and the species was considered common. Here we report a study designed to identify the phylogeographic and conservation genetic parameters of L. aurea. Mitochondrial DNA sequences were examined from 263 individuals sampled from 26 locations using both phylogenetic and population analyses. Despite a general consensus that amphibians are highly structured we found no phylogeographic divisions within the species, however, there was significant structure amongst extant populations (F _ST=0.385). Patterns of haplotype relatedness, high haplotypic diversity (mean h=0.547) relative to low nucleotide diversity (mean π=0.003) and mismatch distribution analysis supported a Pleistocene expansion hypothesis with continued restricted dispersal and gene flow. We conclude that the genetic structure of the species may permit ‘well managed’ intervention to mediate gene flow amongst isolated populations and provide some guidelines for the implementation of such conservation strategies.     

KIF1A, an axonal transporter of synaptic vesicles, is mutated in hereditary sensory and autonomic neuropathy type 2

Hereditary sensory and autonomic neuropathy type II (HSANII) is a rare autosomal-recessive disorder characterized by peripheral nerve degeneration resulting in a severe distal sensory loss. Although mutations in FAM134B and the HSN2 exon of WNK1 were associated with HSANII, the etiology of a substantial number of cases remains unexplained. In addition, the functions of WNK1/HSN2 and FAM134B and their role in the peripheral nervous system remain poorly understood. Using a yeast two-hybrid screen, we found that KIF1A, an axonal transporter of synaptic vesicles, interacts with the domain encoded by the HSN2 exon. In parallel to this screen, we performed genome-wide homozygosity mapping in a consanguineous Afghan family affected by HSANII and identified a unique region of homozygosity located on chromosome 2q37.3 and spanning the KIF1A gene locus. Sequencing of KIF1A in this family revealed a truncating mutation segregating with the disease phenotype. Subsequent sequencing of KIF1A in a series of 112 unrelated patients with features belonging to the clinical spectrum of ulcero-mutilating sensory neuropathies revealed truncating mutations in three additional families, thus indicating that mutations in KIF1A are a rare cause of HSANII. Similarly to WNK1 mutations, pathogenic mutations in KIF1A were almost exclusively restricted to an alternatively spliced exon. This study provides additional insights into the molecular pathogenesis of HSANII and highlights the potential biological relevance of alternative splicing in the peripheral sensory nervous system.