Multiple Phenotypes Resulting from a Mutagenesis Screen for Pharynx Muscle Mutations in Caenorhabditis elegans

Abstract

We describe a novel screen to isolate pharyngeal cell morphology mutants in Caenorhabditis elegans using myo-2::GFP to rapidly identify abnormally shaped pharynxes in EMS (Ethyl Methanesulfonate) mutagenized worms. We observed over 83 C. elegans lines with distinctive pharyngeal phenotypes in worms surviving to the L1 larval stage, with phenotypes ranging from short pharynx, unattached pharynx, missing cells, asymmetric morphology, and non-adherent pharynx cells. Thirteen of these mutations have been chromosomally mapped using Single Nucleotide Polymorphisms (SNPs) and deficiency strain complementation. Our studies have focused on genetically mapping and functionally testing two phenotypes, the short pharynx and the loss of muscle cohesion phenotypes. We have also identified new alleles of sma-1, and our screen suggests many genes directing pharynx assembly and structure may be either pharynx specific or less critical in other tissues.

BLMP-1/Blimp-1 Regulates the Spatiotemporal Cell Migration Pattern in C. elegans

“…In addition, blmp-1 is important for pharynx and [40] male tail morphogenesis [41]. Under Nomarski optics, we confirmed the blmp-1 alae defect, as 40% of blmp-1(s71) mutants had incomplete alae and the rest had no alae in the adult stage (Figure S3C).…”

Development and maintenance of functional actomyosin networks

“…In agreement with previous work in C. elegans (McKeown et al, 1998;Buechner et al, 1999;Norman and Moerman, 2002;Ferrier et al, 2011), we find that UNC-70/β is the dominant isoform in the spermatheca, with SMA-1/βH playing a restricted role. UNC-70/β is expressed throughout the spermatheca and SP-UT valve from L4 and into adulthood and loss of UNC-70/β results in a stronger reduction in spermathecal contractility compared with loss of SMA-1/βH.…”

“…β heavy-spectrin has additional spectrin repeats, a SH3 proteinprotein interaction domain, and unique binding partners and functions (Médina et al, 2002;Lee et al, 2010b). UNC-70/β and SMA-1/βH have distinct expression patterns and subcellular localizations with the expression and function of SMA-1/βH restricted to a specific subset of tissues (McKeown et al, 1998;Buechner et al, 1999;Norman and Moerman, 2002;Ferrier et al, 2011). However, mutations in SMA-1/βH enhance the UNC-70/β loss of function phenotype, indicating the two β isoforms have some overlapping functions (Norman and Moerman, 2002).…”

Developmental genetics of the Caenorhabditis elegans pharynx

“…For example, a screen of 10,000 mutagenized haploid genomes yielded 83 mutants with abnormal pharynges. 113 Specific aspects remain to be understood in detail, including cell fusions 124 and the secretion and deposition of many extracellular components, including glycans, 125 specialized cuticle 126 and chitin. 12 One of the most pressing issues toward a better understanding of axon guidance in the C. elegans pharynx concerns the source and distribution of the guidance cues.…”

“… 14 , 111 , 112 The other identified mutant was a new allele of sma-1 , which encodes a β-spectrin important for pharyngeal muscle development. 113 – 115 A detailed analysis of several other mutants that also affect the properties of the pharyngeal muscles revealed that they impose mechanical constraints that shape the gland cells: mutations in such genes result in abnormal gland cell morphology, including formation of supernumerary branches and swellings suggestive of hypertrophy. This suggests that pharyngeal muscles act primarily to regulate expansion of the gland cells.…”