Alfonso, Aixa et al. (2009) International Worm Meeting "hlh-19 a C. elegans achaete-scute like gene is expressed in the M4 pharyngeal motor neuron."

Ramirez, Oscar, Alfonso, Aixa, Doonan, Ryan

[International Worm Meeting, 2009]

The achaete-scute family of proneural genes has been extensively characterized in Drosophila, and valuable information on the role of these genes in promoting neurogenesis has been obtained. The role of these transcription factors in C. elegans neurogenesis remains relatively uncharacterized. As part of our effort to understand the role of hlh-3 in the differentiation of the hermaphrodite-specific motor neurons (HSNs) (Doonan et al., 2008), we set out to determine the expression pattern of three other achaete-scute-like genes hlh-6, hlh-12, and hlh-19. To determine the identity of the cells that express these proteins, we generated promoter fusion reporter genes. Our first goal was to characterize if they were expressed in the nervous system and whether expression overlapped that of hlh-3. We, as well as others, have shown that two of these genes are not expressed in the nervous system: hlh-6 expression is limited to the pharyngeal gland cells (Raharjo and Gaudet, 2007) and hlh-12 is expressed in the gonadal leader cells (Tamai and Nishiwaki, 2007). Here we report that hlh-19 is expressed in the nervous system. Multiple neurons express the reporter, notably the pharyngeal neuron M4 and what appears to be a subset of sensory neurons in the head of both males and hermaphrodites. Expression is first detected at the comma stage, and continues throughout postembryonic development and adulthood. Interestingly, the reporter is also expressed in the stomatointestinal and body wall muscles of males but not hermaphrodites. We are currently determining the identity of the neurons in the head. Our future goal is to study the role of hlh-19 in the specification and differentiation of the hlh-19 positive neurons. We are currently investigating the consequences of missing gene function using a 218 bp deletion allele of hlh-19 obtained from the National Bioresource Project, Japan. hlh-19 (tm3105), if translated is missing most of the putative DNA binding domain and dimerization region of the protein. Preliminary analysis of hlh-19 (tm3105) revealed no obvious phenotype associated with M4 dysfunction however, the mutant is homozygous viable. References: (1) Doonan, Hatzold, Raut, Conradt, and Alfonso 2008. Mechanisms of Development 125:883-893 (2) Raharjo and Gaudet 2007. Developmental Biology 302:295-308 (3) Tamai and Nishiwaki 2007. Developmental Biology 308:562-571.

Vogel G (2002) Science "Neuroscience. Genes keep neurons' house in order."

Vogel G

[Science, 2002]

As any homeowner knows, timely maintenance is vital for keeping a building functioning properly after construction is finished. The same is evidently true for the complex architecture of the nervous system - at least in the roundworm. On page 686, neuroscientists Oliver Hobert, Oscar Aurelio, and David Hall describe a new family of proteins that help keep the wiring of the worm's nervous system tangle free.

Dolfini D et al. (2012) Crit Rev Biochem Mol Biol "NF-Y and the transcriptional activation of CCAAT promoters."

Gatta R, Mantovani R, Dolfini D

[Crit Rev Biochem Mol Biol, 2012]

The CCAAT box promoter element and NF-Y, the transcription factor (TF) that binds to it, were among the first cis-elements and trans-acting factors identified; their interplay is required for transcriptional activation of a sizeable number of eukaryotic genes. NF-Y consists of three evolutionarily conserved subunits: a dimer of NF-YB and NF-YC which closely resembles a histone, and the "innovative" NF-YA. In this review, we will provide an update on the functional and biological features that make NF-Y a fundamental link between chromatin and transcription. The last 25 years have witnessed a spectacular increase in our knowledge of how genes are regulated: from the identification of cis-acting sequences in promoters and enhancers, and the biochemical characterization of the corresponding TFs, to the merging of chromatin studies with the investigation of enzymatic machines that regulate epigenetic states. Originally identified and studied in yeast and mammals, NF-Y - also termed CBF and CP1 - is composed of three subunits, NF-YA, NF-YB and NF-YC. The complex recognizes the CCAAT pentanucleotide and specific flanking nucleotides with high specificity (Dorn et al., 1997; Hatamochi et al., 1988; Hooft van Huijsduijnen et al, 1987; Kim & Sheffery, 1990). A compelling set of bioinformatics studies clarified that the NF-Y preferred binding site is one of the most frequent promoter elements (Suzuki et al., 2001, 2004; Elkon et al., 2003; Marino-Ramirez et al., 2004; FitzGerald et al., 2004; Linhart et al., 2005; Zhu et al., 2005; Lee et al., 2007; Abnizova et al., 2007; Grskovic et al., 2007; Halperin et al., 2009; Hakkinen et al., 2011). The same consensus, as determined by mutagenesis and SELEX studies (Bi et al., 1997), was also retrieved in ChIP-on-chip analysis (Testa et al., 2005; Ceribelli et al., 2006; Ceribelli et al., 2008; Reed et al., 2008). Additional structural features of the CCAAT box - position, orientation, presence of multiple Transcriptional Start Sites - were previously reviewed (Dolfini et al., 2009) and will not be considered in detail here.

Desse, V. et al. (2019) International Worm Meeting "SAX-7/L1CAM in the maintenance of neuronal architecture."

Perrat, P., Blanchette, C., Desse, V., Benard, C.

[International Worm Meeting, 2019]

Whereas remarkable advances have been made in understanding neuronal development, the mechanisms that maintain the nervous system architecture lifelong are poorly understood. How does the nervous system established during embryogenesis subsequently maintain its integrity throughout life, despite the animal's growth, the addition of new neurons, maturation processes, body movements, and aging? The evolutionarily conserved gene sax-7, homologous to mammalian L1CAM, is one of the factors required for maintaining the structural integrity of ganglia and fascicles in C. elegans1. Thus, sax-7 not only contributes to nervous system development (roles in guidance and fasciculation of a subset of developing neurites)2, but is also required for maintaining the organization of neural architecture after its initial development. Indeed, some neural structures that initially develop normally become disorganized in animals lacking the function of sax-7. With heat shock assays, we show that expression of sax-7S(+) during larval stages is sufficient to rescue the maintenance defects of sax-7 mutants that were devoid of functional sax-7 during nervous system development. We are characterizing a true null allele (generated using CRISPR/Cas9), as well as the expression pattern of a functional SAX-7S::sfGFP (insertion in the endogenous locus using CRISPR/Cas9), and we find that SAX-7S is present in neurons, at the plasma membrane. We are exploring the structure-function relationship of SAX-7S, a transmembrane protein harboring extracellular Ig and FnIII domains, in the context of maintenance of the nervous system architecture. A conditional knockout of L1CAM in the adult mouse brain results in behavioral and learning defects, indicating that L1CAM plays a post-developmental role in mammals as well. Our studies are expected to help understand the role of SAX-7/L1CAM in conserved molecular mechanisms ensuring neuronal maintenance, which may go awry in neurodegenerative conditions. 1 Pocock, Benard et al 2008; Sasakura et al 2005; Wang, Chen et al 2005; Zallen et al 1999; Ramirez-Suarez et al 2019 2 Diaz-Balzac et al 2015; Salzberg et al 2013; Yip and Heiman 2018, Dong et al 2013; Zhu et al 2017