Biomedical subjects

David Patton

Publications and source records attributed to David Patton.

8 recordsLinked to original sources

PubMed2005

Nephrotic plasma alters slit diaphragm-dependent signaling and translocates nephrin, Podocin, and CD2 associated protein in cultured human podocytes.

Podocytes are critical in maintaining the filtration barrier of the glomerulus and are dependent on the slit diaphragm (SD) proteins nephrin, podocin, and CD2-associated protein (CD2AP) to function optimally. The effects of normal human plasma and nephrotic plasma on podocytes were tested, focusing particularly on the SD complex. With the use of a conditionally immortalized human podocyte cell line, it first was shown that exposure to normal and non-nephrotic human plasma leads to a concentration of nephrin, podocin, CD2AP, and actin at the cell surface. Next, the effects of plasma from patients with nephrotic conditions to non-nephrotic conditions were compared. When exposed to all nephrotic plasma samples (and a non-human serum control), nephrin podocin and CD2AP assumed a cytoplasmic distribution; nephrin and synaptopodin were selectively downregulated, and the relocation of nephrin induced by nephrotic plasma could be rescued back to the plasma membrane by co-incubation with non-nephrotic plasma. Furthermore, intracellular calcium signaling was altered by nephrotic plasma, which was mediated by tyrosine kinase phosphorylation. With the use of nephrin mutant human cell lines, it was shown that this signaling and translocation response to normal plasma is nephrin dependent. This work demonstrates that nephrotic plasma seems to be deficient in factors that act via the podocyte SD complex, which are essential in maintaining its physiologic function.

Actins↗

PubMed2005

Prevalence and predictors of "heavy" marijuana use in a Canadian youth sample.

In this investigation, secondary analyses were performed on an extensive database for 473 biological and 128 adoptive families. These data, which were gathered as part of the Vancouver Family Survey, were used to examine the prevalence and predictors of "heavy" marijuana use in a Canadian youth sample aged 14-25. Results in this study showed that 12.6% of the sample reported using marijuana once a week or more. These respondents were categorized as "heavy" marijuana users. Higher levels of life problems were associated with this use pattern. Results from a series of regression analyses suggested that the family, personality, and peer domains all contributed significantly in predicting "heavy" marijuana use. Father's alcoholism and peer illicit drug use had direct relationships with heavy marijuana use in this final model. A possible mediated pathway was also suggested with the Addiction Prone Personality influencing use through its relationship with heavier peer drug use.

Adolescent↗

PubMed2004

A pilot trial of rituximab and alemtuzumab combination therapy in patients with relapsed and/or refractory chronic lymphocytic leukemia (CLL).

The treatment of patients with chronic lymphocytic leukemia (CLL) who fail purine analogues is sub optimal. CLL lymphocytes express two antigens, namely CD 20 and CD 52, for which monoclonal antibodies are readily available. Rituximab is a chimeric monoclonal antibody targeted against CD 20, which has some activity in refractory CLL, with primary effect on nodal disease. Alemtuzumab is a humanized anti-CD 52 antibody that is approved for the treatment of CLL in patients who fail alkylating agents and purine analogues. Alemtuzumab has better activity in the peripheral blood and the bone marrow compared to nodal disease. We investigated whether combining both antibodies is safe in refractory CLL. Both antibodies were given to a total of 12 patients divided into 3 cohorts with escalating alemtuzumab doses (3 mg, 10 mg, and 30 mg). The combination was proven to be safe, not toxic, feasible, and active. One patient attained PR by NCI criteria while all other patients had stable disease lasting a median of 101.5 days. All patients normalized their peripheral lymphocytosis within a median of 23.5 days. No treatment-related mortality was identified. No CMV reactivation occurred. Additional studies are needed to investigate the clinical significance of such a combination in this patient population, and whether this combination can be administered safely with systemic chemotherapy. These studies are currently underway.

Aged↗

PubMed2004

Identification of genes required for embryo development in Arabidopsis.

A long-term goal of Arabidopsis research is to define the minimal gene set needed to produce a viable plant with a normal phenotype under diverse conditions. This will require both forward and reverse genetics along with novel strategies to characterize multigene families and redundant biochemical pathways. Here we describe an initial dataset of 250 EMB genes required for normal embryo development in Arabidopsis. This represents the first large-scale dataset of essential genes in a flowering plant. When compared with 550 genes with other knockout phenotypes, EMB genes are enriched for basal cellular functions, deficient in transcription factors and signaling components, have fewer paralogs, and are more likely to have counterparts among essential genes of yeast (Saccharomyces cerevisiae) and worm (Caenorhabditis elegans). EMB genes also represent a valuable source of plant-specific proteins with unknown functions required for growth and development. Analyzing such unknowns is a central objective of genomics efforts worldwide. We focus here on 34 confirmed EMB genes with unknown functions, demonstrate that expression of these genes is not embryo-specific, validate a strategy for identifying interacting proteins through complementation with epitope-tagged proteins, and discuss the value of EMB genes in identifying novel proteins associated with important plant processes. Based on sequence comparison with essential genes in other model eukaryotes, we identify 244 candidate EMB genes without paralogs that represent promising targets for reverse genetics. These candidates should facilitate the recovery of additional genes required for seed development.

Animals↗

PubMed2004

Arabidopsis hapless mutations define essential gametophytic functions.

In flowering plants, the egg develops within a haploid embryo sac (female gametophyte) that is encased within the pistil. The haploid pollen grain (male gametophyte) extends a pollen tube that carries two sperm cells within its cytoplasm to the embryo sac. This feat requires rapid, precisely guided, and highly polarized growth through, between, and on the surface of the cells of the stigma, style, and ovary. Pollen tube migration depends on a series of long-range signals from diploid female cells as well as a short-range attractant emitted by the embryo sac that guides the final stage of tube growth. We developed a genetic screen in Arabidopsis thaliana that tags mutant pollen with a cell-autonomous marker carried on an insertion element. We found 32 haploid-disrupting (hapless) mutations that define genes required for pollen grain development, pollen tube growth in the stigma and style, or pollen tube growth and guidance in the ovary. We also identified genomic DNA flanking the insertion element for eleven hap mutants and showed that hap1 disrupts AtMago, a gene whose ortholog is important for Drosophila cell polarity.

Arabidopsis↗

PubMed2003

The Arabidopsis SeedGenes Project.

The SeedGenes database (http://www.seedgenes.org) presents molecular and phenotypic information on essential, non-redundant genes of Arabidopsis that give a seed phenotype when disrupted by mutation. Experimental details are synthesized for efficient use by the community and organized into two major sections in the database, one dealing with genes and the other with mutant alleles. The database can be queried for detailed information on a single gene to create a SeedGenes Profile. Queries can also generate lists of genes or mutants that fit specified criteria. The long-term goal is to establish a complete collection of Arabidopsis genes that give a knockout phenotype. This information is needed to focus attention on genes with important cellular functions in a model plant and to assess from a genetic perspective the extent of functional redundancy in the Arabidopsis genome.

Arabidopsis↗

PubMed2002

Condensin and cohesin knockouts in Arabidopsis exhibit a titan seed phenotype.

The titan (ttn) mutants of Arabidopsis exhibit striking alterations in chromosome dynamics and cell division during seed development. Endosperm defects include aberrant mitoses and giant polyploid nuclei. Mutant embryos differ in cell size, morphology and viability, depending on the locus involved. Here we demonstrate that three TTN genes encode chromosome scaffold proteins of the condensin (SMC2) and cohesin (SMC1 and SMC3) classes. These proteins have been studied extensively in yeast and animal systems, where they modulate chromosome condensation, chromatid separation, and dosage compensation. Arabidopsis contains single copies of SMC1 and SMC3 cohesins. We used forward genetics to identify duplicate T-DNA insertions in each gene. These mutants (ttn7 and ttn8) have similar titan phenotypes: giant endosperm nuclei and arrested embryos with a few small cells. A single SMC2 knockout (ttn3) was identified and confirmed by molecular complementation. The weak embryo phenotype observed in this mutant may result from expression of a related gene (AtSMC2) with overlapping functions. Further analysis of titan mutants and the SMC gene family in Arabidopsis should provide clues to chromosome mechanics in plants and insights into the regulation of nuclear activity during endosperm development.

Adenosine Triphosphatases↗

PubMed2002

A high-throughput Arabidopsis reverse genetics system.

A collection of Arabidopsis lines with T-DNA insertions in known sites was generated to increase the efficiency of functional genomics. A high-throughput modified thermal asymmetric interlaced (TAIL)-PCR protocol was developed and used to amplify DNA fragments flanking the T-DNA left borders from approximately 100000 transformed lines. A total of 85108 TAIL-PCR products from 52964 T-DNA lines were sequenced and compared with the Arabidopsis genome to determine the positions of T-DNAs in each line. Predicted T-DNA insertion sites, when mapped, showed a bias against predicted coding sequences. Predicted insertion mutations in genes of interest can be identified using Arabidopsis Gene Index name searches or by BLAST (Basic Local Alignment Search Tool) search. Insertions can be confirmed by simple PCR assays on individual lines. Predicted insertions were confirmed in 257 of 340 lines tested (76%). This resource has been named SAIL (Syngenta Arabidopsis Insertion Library) and is available to the scientific community at www.tmri.org.

Agrobacterium tumefaciens↗