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General Information
D. melanogaster
FlyBase ID
Feature type
Associated gene
Associated Insertion(s)
Carried in Construct
Also Known As
snaIIG05, snaIIG, snaII6, IIG05, snail18
Key Links
Nature of the Allele
Mutations Mapped to the Genome
Additional Notes
Nucleotide change:


Reported nucleotide change:


Amino acid change:

H324Y | sna-PA

Reported amino acid change:



The nucleotide change was reported relative to the positive (noncoding) strand.

Associated Sequence Data
DNA sequence
Protein sequence
Progenitor genotype

Polytene chromosomes normal.

Nature of the lesion

Amino acid replacement: H324Y.

Expression Data
Reporter Expression
Additional Information
Marker for
Reflects expression of
Reporter construct used in assay
Human Disease Associations
Disease Ontology (DO) Annotations
Models Based on Experimental Evidence ( 0 )
Modifiers Based on Experimental Evidence ( 0 )
Comments on Models/Modifiers Based on Experimental Evidence ( 0 )
Disease-implicated variant(s)
Phenotypic Data
Phenotypic Class
Phenotype Manifest In
Detailed Description

sna18 mutants do not exhibit defects in nicotine sensitivity.

sna1/sna18;snaSquish mutant embryos exhibit normal gastrulation.

In sna1/sna18;snaSquish mutant embryos the gland primordia degenerate and disappear.

Ventral cells of sna18 mutants fail to constrict productively during gastrulation.

The class I da neurons of sna18 mutants show dorsal overextension of primary dendrites as well as a severe reduction in lateral branching.

Despite the loss of the caudal visceral mesoderm (CVM) stellate cells still remain though their numbers are strongly reduced.

Malpighian tubules arrest early in their morphogenesis in homozygous embryos. The tubules are similar to those of wild-type embryos just after evagination, but the tubules are typically spherical at stages 16 and 17 (when they are elongated in wild-type embryos). The tip cells are seldom apparent and may be absent. The tubules remain fairly small, apparently ceasing cell division soon after they bud. The hindgut is often normal in shape and length but are sometimes shorter than normal.

Very little ventral cell invagination is seen by mid to late germ band extension.

Patches of wild type cells injected into a twi, sna double mutant embryos undergo typical ventral shape changes, nuclear movements and apical constrictions, as long as they are in a region that would normally be occupied by prospective mesoderm.

The endodermal part of the anterior midgut primordium does not become specified. The stomodeum invaginates almost normally, but no cells attach to its posterior surface and the stomodeum stays epithelial for a long time.

Defective in gonad assembly when in double mutant combination with twi.

In spite of normal AMG and PMG invagination, neither anterior nor posterior midgut primordia shows any sign of extension towards each other, but remain as large mesenchymal cell masses immersed in yolk at the ends of the embryo. The cells of these primordia fail to arrange into an epithelium.

Homozygous embryos do not form a ventral furrow. Mesectodermal domain is expanded.

Interacts with RpII140wimp maternal effect.

sna8 embryos also mutant for twi have a few extra neuroblasts around the midline.

Dorsalized embryos: all cuticle cells along the dorsoventral axis behave like dorsal cells of the wild type embryo. zen expression pattern refines at stage 5, dpp pattern does not refine at all, twi and sna are expressed during late stages of embryogenesis.

No changes in phenotype of tor13D embryos.

Ventral furrow fails to form.

The ventral epithelium becomes thinner, due to the mesodermal cells becoming shorter and more cuboidal, in sna18 mutant embryos at germ band extension. The epithelium then buckles, forming irregular folds. As the germ band elongates, the epithelium straightens out again and the folds disappear. Two deep folds form where the dorsal ectoderm and neuroectoderm meet. Very few morphogenetic changes occur in sna18 Df(2R)twi double mutant embryos, with small transient indentations in the centre of the ventral surface being seen only occasionally.

Homozygous females lay dorsalised eggs.

Strong allele.

Homozygous embryos fail to form a ventral furrow. Cephalic furrow formation, invagination of the endoderm and germ band elongation do take place in these embryos. Embryos show varying defects in the segmental denticle belts.

strong allele

External Data
Show genetic interaction network for Enhancers & Suppressors
Phenotypic Class
NOT Enhancer of
Suppressor of

sna18/sna[+] is a suppressor of visible | dominant phenotype of gcmPyx

Phenotype Manifest In
Suppressed by
NOT suppressed by

sna18 has ventral furrow phenotype, non-suppressible by esgsna.PA

sna18 has ventral furrow phenotype, non-suppressible by worsna.PA

Enhancer of
Suppressor of

sna18/sna[+] is a suppressor of chaeta | increased number phenotype of gcmPyx

Additional Comments
Genetic Interactions

The addition of a Df(3L)H99 background (blocking apoptosis), results in the survival of the corpora allata and prothoracic glands in sna1/sna18;snaSquish mutant embryos, but they do not undergo epithelial-mesenchymal transition. As a result, the gland primordia maintain epithelial polarity, do not migrate, and form small pouches that remain attached to the epidermis.

sna18 is a moderate enhancer of the ImpScer\UAS.cGa (Scer\GAL4mat.αTub67C.T:Hsim\VP16) dorsalisation phenotype.

The stomatogastric nervous system is intact in twi3 sna18 double mutant stage 16 embryos, but the corpus cardiacum is absent.

sna18 Df(2R)twi embryos do not form a ventral furrow. brkM68; dppH46 sna18 Df(2R)twi quadruple mutant embryos secrete cuticles showing partial transformation of ventral into dorsal epidermis.

Heat-induced foghs.PM expression fails to induce ventral furrow formation, cells do exhibit apical flattening.

Embryos mutant for both sna and twi do not form an anterior midgut or a stomodeum.

Xenogenetic Interactions
Complementation and Rescue Data
Partially rescued by

sna18/sna1 is partially rescued by sna24.8.GFP

sna18/sna1 is partially rescued by snaΔProx

sna18 is partially rescued by snasna.mutR

sna18 is partially rescued by snasna.ΔM1


At 25[o]C, snaΔProx rescues 82% of sna1/sna18 animals to viability. At 18[o]C, 94% are rescued and at 29[o]C 36% are rescued.

At 25[o]C, sna+t24.8 rescues 91% of sna1/sna18 animals to viability. At 18[o]C, 100% are rescued and at 29[o]C 100% are rescued.

snaSquish and snaDtoP each rescue the gastrulation defects of sna1/sna18 embryos, but the animals are not rescued to adult viability.

Images (0)
Stocks (4)
Notes on Origin


C. Nusslein-Volhard.

External Crossreferences and Linkouts ( 0 )
Synonyms and Secondary IDs (13)
Reported As
Symbol Synonym
Name Synonyms
Secondary FlyBase IDs
    References (80)