Biomedical subjects

C Echeverri

Publications and source records attributed to C Echeverri.

5 recordsLinked to original sources

PubMed2003

A functional genomic analysis of cell morphology using RNA interference.

BACKGROUND: The diversity of metazoan cell shapes is influenced by the dynamic cytoskeletal network. With the advent of RNA-interference (RNAi) technology, it is now possible to screen systematically for genes controlling specific cell-biological processes, including those required to generate distinct morphologies. RESULTS: We adapted existing RNAi technology in Drosophila cell culture for use in high-throughput screens to enable a comprehensive genetic dissection of cell morphogenesis. To identify genes responsible for the characteristic shape of two morphologically distinct cell lines, we performed RNAi screens in each line with a set of double-stranded RNAs (dsRNAs) targeting 994 predicted cell shape regulators. Using automated fluorescence microscopy to visualize actin filaments, microtubules and DNA, we detected morphological phenotypes for 160 genes, one-third of which have not been previously characterized in vivo. Genes with similar phenotypes corresponded to known components of pathways controlling cytoskeletal organization and cell shape, leading us to propose similar functions for previously uncharacterized genes. Furthermore, we were able to uncover genes acting within a specific pathway using a co-RNAi screen to identify dsRNA suppressors of a cell shape change induced by Pten dsRNA. CONCLUSIONS: Using RNAi, we identified genes that influence cytoskeletal organization and morphology in two distinct cell types. Some genes exhibited similar RNAi phenotypes in both cell types, while others appeared to have cell-type-specific functions, in part reflecting the different mechanisms used to generate a round or a flat cell morphology.

Animals↗

PubMed2001

Fite stain positivity in Rhodococcus equi: yet another acid-fast organism in respiratory cytology--a case report.

Rhodococcus equi is an aerobic Gram-positive and acid-fast coccobacillus that may cause cavitary pneumonia in immunocompromised hosts such as HIV-infected patients. Numerous Grocott's methenamine silver (GMS)-positive organisms were initially noted on the direct smear; a minor number of acid-fast organisms were seen in the Thin-Prep slide. Since the abundant mucous material with the attached organisms seen in conventional smears may be lost in liquid-based preparations, more sensitive stains such as Fite, as well as a more diligent search for organisms, is needed. This case illustrates the importance of careful selection and evaluation of special stains in sputum specimens.

AIDS-Related Opportunistic Infections↗

PubMed2001

Vulvar keratinizing squamous cell carcinoma in a 26-year-old woman.

A 26-year-old Hispanic woman complaining of "itching" and "herpetic lesions" on the vulva for 9 months was seen at a university hospital. On physical examination, multiple vulvar masses were noted. Biopsies taken from these lesions showed invasive keratinizing squamous cell carcinoma. The vulvectomy specimen revealed 4 tumor masses, the largest located on the mons pubis. Although the incidence of vulvar intraepithelial neoplasia has increased in recent years, only very few cases of invasive carcinoma have been reported in young women. The tumors that occur at a younger age characteristically have basaloid or warty histology, in contrast to those occurring in older women, which usually are well-differentiated keratinizing carcinomas. We believe this is an unusual case of vulvar squamous cell carcinoma. In addition to our patient's young age, her tumor had a histologic profile usually found in lesions of an elderly woman. The tumor was negative for human papillomavirus by polymerase chain reaction analysis and was positive for p53 by immunohistochemistry.

Adult↗

PubMed2000

Functional genomic analysis of cell division in C. elegans using RNAi of genes on chromosome III.

Genome sequencing projects generate a wealth of information; however, the ultimate goal of such projects is to accelerate the identification of the biological function of genes. This creates a need for comprehensive studies to fill the gap between sequence and function. Here we report the results of a functional genomic screen to identify genes required for cell division in Caenorhabditis elegans. We inhibited the expression of approximately 96% of the approximately 2,300 predicted open reading frames on chromosome III using RNA-mediated interference (RNAi). By using an in vivo time-lapse differential interference contrast microscopy assay, we identified 133 genes (approximately 6%) necessary for distinct cellular processes in early embryos. Our results indicate that these genes represent most of the genes on chromosome III that are required for proper cell division in C. elegans embryos. The complete data set, including sample time-lapse recordings, has been deposited in an open access database. We found that approximately 47% of the genes associated with a differential interference contrast phenotype have clear orthologues in other eukaryotes, indicating that this screen provides putative gene functions for other species as well.

Animals↗

PubMed1999

Opposing motor activities of dynein and kinesin determine retention and transport of MHC class II-containing compartments.

MHC class II molecules exert their function at the cell surface by presenting to T cells antigenic fragments that are generated in the endosomal pathway. The class II molecules are targetted to early lysosomal structures, termed MIIC, where they interact with antigenic fragments and are subsequently transported to the cell surface. We previously visualised vesicular transport of MHC class II-containing early lysosomes from the microtubule organising centre (MTOC) region towards the cell surface in living cells. Here we show that the MIIC move bidirectionally in a 'stop-and-go' fashion. Overexpression of a motor head-deleted kinesin inhibited MIIC motility, showing that kinesin is the motor that drives its plus end transport towards the cell periphery. Cytoplasmic dynein mediates the return of vesicles to the MTOC area and effectively retains the vesicles at this location, as assessed by inactivation of dynein by overexpression of dynamitin. Our data suggest a retention mechanism that determines the perinuclear accumulation of MIIC, which is the result of dynein activity being superior over kinesin activity. The bidirectional nature of MIIC movement is the result of both kinesin and dynein acting reciprocally on the MIIC during its transport. The motors may be the ultimate targets of regulatory kinases since the protein kinase inhibitor staurosporine induces a massive release of lysosomal vesicles from the MTOC region that is morphologically similar to that observed after inactivation of the dynein motor.

Antibodies↗