WormMine: ExpressionPattern Expr1425

• Pattern: sma-1 transcripts are present in the embryonic epidermis at the start of morphogenesis. In a population of mixed-stage embryos hybridized with a sma-1 antisense probe, sma-1 RNA was not observed in pre-morphogenesis embryos. In particular, there was no sign of sma-1 transcripts in early cleavage-stage embryos (2-8 cells). In embryos just beginning morphogenesis, sma-1 RNA was present in cells along the dorsal surface of the embryo, corresponding to the location of the epidermis at this point in development. Examining embryos at successive stages of morphogenesis, it was found that sma-1 RNA changed in a pattern that exactly matched the movements of the migrating epidermal cells. During early morphogenesis, when the epidermal cell sheet spreads over the lateral surfaces of the embryo, sma-1-expressing cells were observed on the dorsal and lateral surfaces of the embryo, but not on the ventral surface or in the head region, which at this stage are not yet covered by the spreading epidermis. In cross-section, it can be seen that the sma-1 RNA is located in the outermost cell layer of the embryo. As morphogenesis progresses, the spreading epidermis encloses first the ventral surface of the embryo and then the head as the embryo bends ventrally and begins to elongate. In embryos at this stage of morphogenesis, there was a corresponding pattern in which sma-1 RNA was seen first on the ventral surface and then on the anterior (head) surface of the embryo. At the same time, the overall level of sma-1 RNA rapidly decreased as the embryo began to elongate. sma-1 RNA in the epidermis was not observed in embryos past the 2-fold stage. In addition to sma-1 expression in the cells of the epidermis, a line of sma-1 RNA was observed in the interior of the embryo, oriented along the anterior-posterior axis. Based on its location, this sma-1 RNA seems located in the developing digestive tract of the embryo, consisting of the pharynx and intestine. During early morphogenesis, it is difficult to determine the anterior extent of sma-1 staining in the interior of the embryo, but as the embryo begins to elongate, the level of sma-1 RNA increases and at the 1.5-fold stage sma-1 RNA is clearly present in both the pharynx and intestine. A lower level of pharyngeal/intestinal RNA was observed in 2- to 3-fold stage embryos. In these older embryos, sma-1 RNA was also found in the excretory cell and in an unidentified cell near the anus. Expression of sma-1 RNA was observed in several epithelial tissues: epidermis, pharynx, intestine and excretory cell. sma-1 RNA was not seen in the body wall muscle cells, which are arranged in four stripes underlying the epidermis. The highest level of sma-1 RNA was observed in the epidermis during the early stages of morphogenesis, prior to when differences are observed between development of wild-type and sma-1 embryos.
• Primary Identifier: Expr1425

4 Anatomy Terms

Definition	Name	Synonym	Primary Identifier
A chain of very large cuboidal cells forming a wide central lumen in which food arrives from the posterior pharynx, is digested, and from which waste products proceed to the rectum. Intestinal rings form in groups of two and four cells surrounding the common lumen; thus the epithelium is only one cell deep at any point, with neighboring cells firmly secured to their neighbors by apical adherens junctions. These cells have very large nuclei and many large vacuoles, yolk granules, and other inclusions; the latter increase in number and electron density as the animal ages.	intestine	gut	WBbt:0005772
the feeding organ, a neuro-muscular pump in the head of the animal, used to ingest food, bacteria suspended in liquid, filter them out, grind them up and transport posteriorly into the instestine.	pharynx	esophagus	WBbt:0003681
H-shaped cell associated with the excretory system, largest cell in C. elegans.	excretory cell	excretory canal cell	WBbt:0005812
cell that exists in and is part of an embryo.	embryonic cell		WBbt:0007028

1 Genes

WormBase Gene ID	Gene Name	Sequence Name	Organism
WBGene00004855	sma-1	R31.1	Caenorhabditis elegans

1 Life Stages

Remark	Definition	Other Name	Public Name	Primary Identifier
	The whole period of embryogenesis in the nematode Caenorhabditis elegans, from the formation of an egg until hatching.		embryo Ce	WBls:0000003