Microphthalmia belongs to a group of congenital eye malformations. In Irish soft-coated wheaten terriers (ISCWTs), an amino acid deletion in the retinol-binding protein 4 (RBP4) was identified as cause of the disease. Normal RBP4 carries vitamin A from hepatic stores to peripheral tissues, including the placenta and eye. There it is used as substrate for synthesis of retinoic acid, an important molecule for proper tissue development. The mutation disrupts folding of the retinol-binding protein which decreases its secretion from hepatocytes to serum, resulting in gestational vitamin A deficiency. The eye is most sensitive to impaired synthesis of retinoic acid among organs and vitamin A deficiency is a known risk factor for ocular birth defects. Inheritance of the disease is unusual. It is an autosomal recessive trait, but it is only expressed, when both dam and offspring are deletion homozygotes. Normal RBP carries vitamin A to and from cells of the materno-fetal interface. Only if maternal and fetal RBP4 mutations are homozygous, the vitamin A level is reduced below the threshold for expression of the disease in the offspring.
Test specific information
Symptoms will develop at a young age. Within a few hours to a maximum of several weeks after birth, the characteristics that go with these genetic effects will become visible.
Turn Around Time
The turn-around-time of a test depends to a large extent on the logistics of sample transportation to the laboratory. After receiving the sample at the test location, you can normally expect the result within 10 working days. A longer delivery time applies to tests carried out by a Partner Lab.
Location of disease or trait
This disease is present in the entire body, but causes main effects in the internal organs such as stomach, intestinal tract, liver and / or kidneys. In a number of cases, the disease affects one major internal organ.
This DNA test is available for the following breeds: . Additional information is available in the Frequently Asked Questions (FAQ).
For this DNA test we accept the following materials: Blood EDTA, Blood Heparin, Semen, Swab, Tissue. Please contact Dr. Van Haeringen Laboratorium if you wish to submit other material as listed.
An animal can be free and has in that situation two healthy alleles. When used in breeding this animal will not become ill due to the disease. It cannot spread the disease in the population.
An animal can be carrier and has in that situation one healthy and one disease allele. When used in breeding 50 percent of the offspring will receive the disease allele. Carriers will not become ill.
An animal can be affected and has in that situation two disease alleles. When used in breeding all offspring will also receive the disease allele. Affected will become ill.
This genetic factor is inherited in an autosomal, recessive, mode. This means, that the individual can be free of the disease (homozygote normal), affected (homozygous affected) or carrier (heterozygous).
Carriers may spread the mutation in a population without showing symptoms themselves. Because of this, it is extremely important to identify carriers correctly to prevent spreading of a mutation.
Severity of Disease