Identification of genes expressed in C. elegans touch receptor neurons

Abstract

The extent of gene regulation in cell differentiation is poorly understood. We previously used saturation mutagenesis to identify 18 genes that are needed for the development and function of a single type of sensory neuron--the touch receptor neuron for gentle touch in Caenorhabditis elegans. One of these genes, mec-3, encodes a transcription factor that controls touch receptor differentiation. By culturing and isolating wild-type and mec-3 mutant cells from embryos and applying their amplified RNA to DNA microarrays, here we have identified genes that are known to be expressed in touch receptors, a previously uncloned gene (mec-17) that is needed for maintaining touch receptor differentiation, and more than 50 previously unknown mec-3-dependent genes. These genes are randomly distributed in the genome and under-represented both for genes that are co-expressed in operons and for multiple members of gene families. Using regions 5' of the start codon of the first 20 genes, we have also identified an over-represented heptanucleotide, AATGCAT, that is needed for the expression of touch receptor genes.

Molecular profiling reveals synaptic release machinery in Merkel cells

“…In this study, we have surmounted these obstacles by combining genetic labeling, in vitro methods, and microarray techniques to identify 362 transcripts that are enriched in Merkel cells. A similar strategy has been used to discover genes expressed in worm touch receptors (40). To our knowledge, this report represents the first extensive molecular profiling of Merkel cells, and it provides a rich data set of molecules that help to define the Merkel cell's function in the epidermis.…”

Touch sensitivity in Caenorhabditis elegans

“…UNC-86::MEC-3 heterodimers then bind promoters of mec-3 and other genes, maintaining mec-3 expression and activating transcription of downstream genes necessary for touch receptor neuron function [24,94]. The requirement for mec-3 for touch neuron differentiation has been used to identify additional mec-3-dependent genes using DNA microarrays [99]. The roles of most of these new genes in touch sensitivity have not been tested.…”

“…Screens for touch-insensitive mutants have identified many genes whose products are needed for touch sensitivity, but even though these screens are saturated, they cannot give a complete picture of the genes needed for touch sensitivity. Microarray analysis of RNAs expressed in the touch receptor neurons have provided many more candidate genes [99], but their importance in transduction has not been determined. Second, we do not know how that channel complex interacts with the ECM, nor how the ECM is structured.…”

“…Although the sensory neurons and putative channels responsible for many of these behaviors have been identified, the means by which they sense mechanical stimuli has yet to be ascertained. Genetic approaches, using both classical procedures [9] and improved RNA interference methods [42], as well as DNA microarray methods (e.g., [99]) should provide additional candidates for components of the transduction machinery in these cells. Wild-type and mutant strains can then be analyzed by calcium imaging, as has been done with the ASH neurons needed for nose touch [34] and the DVA neuron needed for proprioreception [48], and direct electrophysiological recording to obtain a description of the mechanosensory currents in these sensory neurons.…”

Molecular basis of the acetyltransferase activity of MEC-17 towards α-tubulin

“…Previously, the Chalfie group reported two missense mutations in allele of C. elegans MEC-17, u265, one of which (Leu46) corresponds to Gln53 of DrMEC-17 [9]. Intriguingly, although the acetyltransferase activity of MEC-17 is not required for touch sensation [10], the mec-17 (u265) worms are not touch sensitive [9], indicating that Leu46 of C. elegans MEC-17 and probably the equivalent Gln53 of DrMEC-17 might contribute to the substrate binding.…”