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The LIM homeobox gene ceh-14 is required for phasmid function and neurite outgrowth
Universität Basel, Basel, Switzerland /National Institute of Genetics, Shizuoka, Japan / Research Organization of Information and Systems (ROIS), Tokyo, Japan.
Universität Basel, Basel, Switzerland.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Biology. Karolinska Institute.
Aix-Marseille Université, Marseille, France.
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2013 (English)In: Developmental Biology, ISSN 0012-1606, E-ISSN 1095-564X, Vol. 380, no 2, 314-323 p.Article in journal (Refereed) Published
Abstract [en]

Transcription factors play key roles in cell fate specification and cell differentiation. Previously, we showed that the LIM homeodomain factor CEH-14 is expressed in the AFD neurons where it is required for thermotaxis behavior in Caenorhabditis elegans. Here, we show that ceh-14 is expressed in the phasmid sensory neurons, PHA and PHB, a number of neurons in the tail, i.e., PHC, DVC, PVC, PVN, PVQ PVT, PVW and PVR, as well as the touch neurons. Analysis of the promoter region shows that important regulatory elements for the expression in most neurons reside from -4 kb to -1.65 kb upstream of the start codon. Further, within the first introns are elements for expression in the hypodermis. Phylogenetic footprinting revealed numerous conserved motifs in these regions. In addition to the existing deletion mutation ceh-14(ch3), we isolated a new allele, ceh-14(ch2), in which only one LIM domain is disrupted. The latter mutant allele is partially defective for thermosensation. Analysis of both mutant alleles showed that they are defective in phasmid dye-filling. However, the cell body, dendritic outgrowth and ciliated endings of PHA and PHB appear normal, indicating that ceh-14 is not required for growth. The loss of a LIM domain in the ceh-14(ch2) allele causes a partial loss-of-function phenotype. Examination of the neurites of ALA and tail neurons using a ceh-14::GFP reporter shows abnormal axonal outgrowth and pathfinding.

Place, publisher, year, edition, pages
2013. Vol. 380, no 2, 314-323 p.
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:sh:diva-19637DOI: 10.1016/j.ydbio.2013.04.009ISI: 000322297900015PubMedID: 23608457ScopusID: 2-s2.0-84879881843OAI: oai:DiVA.org:sh-19637DiVA: diva2:644685
Note

Som manuskript i avhandling. As manuscript in dissertation.

Available from: 2013-09-02 Created: 2013-09-02 Last updated: 2016-03-14Bibliographically approved
In thesis
1. Regulatory function of homeobox genes in the development of Caenorhabditis elegans
Open this publication in new window or tab >>Regulatory function of homeobox genes in the development of Caenorhabditis elegans
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The nematode worm Caenorhabditis elegans has been widely used as a genetic model for over 40 years to investigate developmental control genes. In this thesis, I studied the roles of several homeobox genes and a novel RNA binding protein (RBD) in the development of C. elegans to understand the function of these genes in higher organisms. Homeobox genes are transcriptional regulators that are highly conserved in evolution and play important domains in eukaryotes, and genes encoding this domain play roles in a wide variety of post-transcriptional gene regulation processes. In paper I, we characterized a novel protein, RNA binding domain-1 (RBD-1), which is involved in ribosome biogenesis. This protein contains six consensus RNA-binding domains and is conserved as to sequence, domain organization, and subcellular localization from yeast to human. RBD-1 is essential for the development of C. elegans. The RNAi experiments using the cDNA of RBD-1 demonstrated various abnormalities in the C. elegans development, such as defects in morphology (dumpy), incomplete molting, and defective gonadal and vulval development. Animals depleted for RBD-1 arrested mainly at the L1 larval stage. In the course of studying the homeobox genes, we often used the dye-filling assay. It is the simplest method presently used to assay the structural integrity of sensory cilia. In paper II, we optimized conditions, in which reliable staining of the inner labial (IL2) neurons could be obtained, namely in low salt conditions, in the presence of determethod to distinguish mutant alleles that stain amphids and phasmids, and IL2 neurons. Using this assay, we found that a mutation in the POU homeobox gene unc-86 abolished dye-filling in IL2 neurons but not amphids and phasmids. mids. In Paper III, we showed that the LIM homeobox gene ceh-14 was expressed in other sensory neurons and interneurons, including the phasmid neurons and the ALA interneuron, while previously it was shown that ceh-14 is expressed in the AFD neurons and required for thermotaxis behavior in C. elegans. ceh-14 mutant animals displayed defects in dendrite outgrowth of the phasmid neurons, while the ALA interneuron and some tail neurons showed ceh-14 and the paired-like homeobox gene ceh-17 act in the separate pathway to control normal axonal outgrowth of ALA neuron. Overexpression of CEH-14 in the nervous system may titrate out interacting factors, such as LDB-1, which caused developmental defects In paper IV, we investigated the function of four homeobox genes, ceh-6, ceh-26, ttx-1 and ceh-37, in the excretory cell development. We showed that the POU-III class homeobox gene ceh-6, the Prospero class homeobox gene ceh-26, and two otd/Otx family homeobox genes, ceh-37 and ttx-1 formed a regulatory hierarchy required for the development and function of the excretory cell in C. elegans. The excretory cell is required for maintaining osmotic balance and excreting waste products. While ceh-6 has previously been demonstrated to play a role in the excretory cell patterning, we showed here that ceh-26 and ceh-37 are expressed in the excretory cell. ceh-26 mutants arrested in early larval development with defects characteristic for a lack of excretory cell function. Double mutant of the otd/Otx genes ceh-37 and ttx-1 was displaying larval arrest, consistent with the excretory cell dysfunction, which indicates that there is functional redundancy between these two genes. Using mutant alleles and RNAi, we showed that ceh-26::GFP and ceh-37::GFP was down-regulated in ceh-6 mutants. Further, we found that ceh-37::GFP was down-regulated in the ceh-26 genes, such as channel proteins (the target genes ) that are expressed in the excretory cell and found that only a subset of the genes regulated by ceh-6 was also regulated by ceh-37/ttx-1. We mapped the promoter regions of ceh-26 and of the target gene clh-4 to identify putative homeodomain proteins binding sites. Given that these homeobox genes are well conserved in evolution, we may expect that parts of this cascade are also conserved in other organisms.

Place, publisher, year, edition, pages
Stockholm: Karolinska Institutet, 2010. 47 p.
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:sh:diva-29738 (URN)978-91-7457-018-2 (ISBN)
Available from: 2016-03-14 Created: 2016-03-14 Last updated: 2016-03-14Bibliographically approved

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