Screening for Presenilin Inhibitors Using the Free-Living Nematode, Caenorhabditis elegans

Abstract

Caenorhabditis elegans contains 3 homologs of presenilin genes that are associated with Alzheimer's disease. Loss-offunction mutations in C. elegans genes cause a defect in egg laying. In humans, loss of presenilin-1 (PS1) function reduces amyloid-beta peptide processing from the amyloid protein precursor. Worms were screened for compounds that block egg laying, phenocopying presenilin loss of function. To accommodate even relatively high throughput screening, a semiautomated method to quantify egg laying was devised by measuring the chitinase released into the culture medium. Chitinase is released by hatching eggs, but little is shed into the medium from the body cavity of a hermaphrodite with an egg laying deficient (egl) phenotype. Assay validation involved measuring chitinase release from wild-type C. elegans (N2 strain), sel-12 presenilin loss-of-function mutants, and 2 strains of C. elegans with mutations in the egl-36 K + channel gene. Failure to find specific presenilin inhibitors in this collection likely reflects the small number of compounds tested, rather than a flaw in screening strategy. Absent defined biochemical pathways for presenilin, this screening method, which takes advantage of the genetic system available in C. elegans and its historical use for anthelminthic screening, permits an entry into mechanismbased discovery of drugs for Alzheimer's disease. (Journal of Biomolecular Screening 2004:147-152)

Automated High-Content Live Animal Drug Screening Using C. elegans Expressing the Aggregation Prone Serpin α1-antitrypsin Z

“…This bottleneck is evident in the first series of relatively low-throughput and labor-intensive C. elegans drug screens [28], [29], [33], [55], [56]. Compound effects were assessed by direct inspection of animals in microtiter plate wells using a stereomicroscope or of images captured by a CCD camera.…”

“…Moreover, operator fatigue increases variability and decreases specificity. An enzymatic assay that measures fluorescent substrate conversion in culture medium can be automated, but the effects of compounds on the whole animal are lost [55]. Recently, Moy et al, reported an automated high-throughput screen for novel antimicrobial compounds that protect C. elegans from a lethal dose of S. faecalis [31].…”

High‐throughput screening and small animal models, where are we?

“…With traditional equipment, several other events may be measured in an automatic manner. For example, to measure egg-laying behaviour of C. elegans, a pharmaceutical company has developed an indirect method, called the 'chitinase assay' (Ellerbrock et al, 2004). It consists of measuring the chitinase activity that is released from the eggs by hatching larvae.…”

A microfluidic device for whole-animal drug screening using electrophysiological measures in the nematode C. elegans

“…Readouts fall into two broad categories: (1) assessment of the quantity or anatomical disposition of a fluorescent marker at the cellular 12–14 or organismal 15, 16 level, and (2) quantification of stereotypic behaviors such as crawling, 17, 18 swimming, 19, 20 or egg laying. 21 …”