Strabismus was originally identified as a Drosophila

Drosophila

Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" or more appropriately pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species to linger around overripe or rotting fruit...

protein involved in planar cell polarity. Flies with mutated stranismus genes have altered development of omatidia

Ommatidium

The compound eyes of insects, mantis shrimp and millipedes are composed of units called ommatidia . An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells. The outer part of the ommatidium is overlaid with a transparent cornea...

 in their eyes. Vertebrate

Vertebrate

Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s have two Strabismus-related proteins, VANGL1 and VANGL2 (an alternate name for the Drosophila "Strabismus" protein is "Van Gogh").

The amino acid sequence and localization studies for Strabismus indicate that it is a membrane protein

Membrane protein

A membrane protein is a protein molecule that is attached to, or associated with the membrane of a cell or an organelle. More than half of all proteins interact with membranes.-Function:...

. Prickle

Prickle (protein)

The first prickle protein was identified in Drosophila as a planar cell polarity protein. Vertebrate prickle-1 was first found as a rat protein that binds to a transcription factor, neuron-restrictive silencer factor . It was then recognized that other vertebrates including mice and humans have two...

 is another protein in the planar cell polarity signaling pathway. Prickle is recruited to the cell

Cell (biology)

The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

 surface membrane

Cell membrane

The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...

 by strabismus. In cells of the developing Drosophila wing, Prickle and Strabismus are concentrated at the cell surface membrane on the most proximal side of cells.

Vertebrate cell movement

VANGL2 is involved in the migration of groups of cells during vertebrate embryogenesis.

Humans

In humans, mutations in VANGL1 have been associated with neural tube defects including spina bifida

Spina bifida

Spina bifida is a developmental congenital disorder caused by the incomplete closing of the embryonic neural tube. Some vertebrae overlying the spinal cord are not fully formed and remain unfused and open. If the opening is large enough, this allows a portion of the spinal cord to protrude through...

, and with some forms of cancer

Cancer

Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

 including hepatocellular carcinoma

Hepatocellular carcinoma

Hepatocellular carcinoma is the most common type of liver cancer. Most cases of HCC are secondary to either a viral hepatitide infection or cirrhosis .Compared to other cancers, HCC is quite a rare tumor in the United States...

.