Ptpmeg is required for the proper establishment and maintenance of axon projections in the central brain of Drosophila

Ptpmeg is a cytoplasmic tyrosine phosphatase containing FERM and PDZ domains. Drosophila Ptpmeg and its vertebrate homologs PTPN3 and PTPN4 are expressed in the nervous system, but their developmental functions have been unknown. We found that ptpmeg is involved in neuronal circuit formation in the Drosophila central brain, regulating both the establishment and the stabilization of axonal projection patterns. In ptpmeg mutants, mushroom body (MB) axon branches are elaborated normally, but the projection patterns in many hemispheres become progressively abnormal as the animals reach adulthood. The two branches of MB α/βneurons are affected by ptpmeg in different ways; ptpmegactivity inhibits α lobe branch retraction while preventing β lobe branch overextension. The phosphatase activity of Ptpmeg is essential for bothα and β lobe formation, but the FERM domain is required only for preventing α lobe retraction, suggesting that Ptpmeg has distinct roles in regulating the formation of α and β lobes. ptpmeg is also important for the formation of the ellipsoid body (EB), where it influences the pathfinding of EB axons. ptpmeg function in neurons is sufficient to support normal wiring of both the EB and MB. However, ptpmeg does not act in either MB or EB neurons, implicating ptpmeg in the regulation of cell-cell signaling events that control the behavior of these axons.

CD4+ T cell-independent DNA vaccination against opportunistic infections

Depletion or dysfunction of CD4+ T lymphocytes profoundly perturbs host defenses and impairs immunogenicity of vaccines. Here, we show that plasmid DNA vaccination with a cassette encoding antigen (OVA) and a second cassette encoding full-length CD40 ligand (CD40L), a molecule expressed on activated CD4+ T lymphocytes and critical for T cell helper function, can elicit significant titers of antigen-specific immunoglobulins in serum and Tc1 CD8+ T cell responses in CD4-deficient mice. To investigate whether this approach leads to CD4+ T cell-independent vaccine protection against a prototypic AIDS-defining infection, Pneumocystis (PC) pneumonia, we used serum from mice vaccinated with PC-pulsed, CD40L-modified DCs to immunoprecipitate PC antigens. Kexin, a PC antigen identified by this approach, was used in a similar DNA vaccine strategy with or without CD40L. CD4-deficient mice receiving DNA vaccines encoding Kexin and CD40L showed significantly higher anti-PC IgG titers as well as opsonic killing of PC compared with those vaccinated with Kexin alone. Moreover, CD4-depleted, Kexin-vaccinated mice showed a 3-log greater protection in a PC challenge model. Adoptive transfer of CD19+ cells or IgG to SCID mice conferred protection against PC challenge, indicating a role of humoral immunity in the protection. The results of these studies show promise for CD4-independent vaccination against HIV-related or other opportunistic pathogens.

Compartmentalization of visual centers in the Drosophila brain requires Slit and Robo proteins

Brain morphogenesis depends on the maintenance of boundaries between populations of non-intermingling cells. We used molecular markers to characterize a boundary within the optic lobe of the Drosophila brain and found that Slit and the Robo family of receptors, well-known regulators of axon guidance and neuronal migration, inhibit the mixing of adjacent cell populations in the developing optic lobe. Our data suggest that Slit is needed in the lamina to prevent inappropriate invasion of Robo-expressing neurons from the lobula cortex. We show that Slit protein surrounds lamina glia, while the distal cell neurons in the lobula cortex express all three Drosophila Robos. We examine the function of these proteins in the visual system by isolating a novel allele of slit that preferentially disrupts visual system expression of Slit and by creating transgenic RNA interference flies to inhibit the function of each Drosophila Robo in a tissue-specific fashion. We find that loss of Slit or simultaneous knockdown of Robo, Robo2 and Robo3 causes distal cell neurons to invade the lamina, resulting in cell mixing across the lamina/lobula cortex boundary. This boundary disruption appears to lead to alterations in patterns of axon navigation in the visual system. We propose that Slit and Robo-family proteins act to maintain the distinct cellular composition of the lamina and the lobula cortex.

High-resolution cartography of recently integrated human chromosome 19-specific Alu fossils

The recently inserted subfamilies of Alu retroposons (Ya5/8 and Yb8) are composed of approximately 2000 elements. We have screened a human chromosome 19-specific cosmid library for the presence of Ya5/8 and Yb8 Alu family members. This analysis resulted in the identification of 12 Ya5/8 Alu family members and 15 Yb8 Alu family members from human chromosome 19. The total number of Ya5/8 and Yb8 Alu family members located on human chromosome 19 does not differ from that expected based upon random integration of Alu repeats within the human genome. The distribution of both subfamilies of Alu elements along human chromosome 19 also appears to be random. DNA sequence analysis of the individual Alu elements revealed a low level of random mutations within both subfamilies of Alu elements consistent with their recent evolutionary origin. Oligonucleotide primers complementary to the flanking unique sequences adjacent to each Alu element were used in polymerase chain reaction assays to determine the phylogenetic distribution and human genomic variation associated with each Alu family member. All of the chromosome 19-specific Ya5/8 and Yb8 Alu family members were restricted to the human genome and absent from orthologous positions within the genomes of several non-human primates. Three of the Yb8 Alu family members were polymorphic for insertion presence/absence within the genomes of a diverse array of human populations. The polymorphic Alu elements will be useful tools for the study of human population genetics.

Assembly of a high-resolution map of the Acadian Usher syndrome region and localization of the nuclear EF-hand acidic gene

Usher syndrome type 1C (USH1C) occurs in a small population of Acadian descendants from southwestern Louisiana. Linkage and linkage disequilibrium analyses localize USH1C to chromosome 11p between markers D11S1397 and D11S1888, an interval of less than 680 kb. Here, we refine the USH1C linkage to a region less than 400 kb, between genetic markers D11S1397 and D11S1890. Using 17 genetic markers from this interval, we have isolated a contiguous set of 60 bacterial artificial chromosomes (BACs) that span the USH1C critical region. Exon trapping of BAC clones from this region resulted in the recovery of an exon of the nuclear EF-hand acidic (NEFA) gene. However, DNA sequence analysis of the NEFA cDNA from lymphocytes of affected individuals provided no evidence of mutation, making structural mutations in the NEFA protein unlikely as the cellular cause of Acadian Usher syndrome.