Maternal Inheritance of a Recessive RBP4 Defect in Canine Congenital Eye Disease.

Maternally skewed transmission of traits has been associated with genomic imprinting and oocyte-derived mRNA. We report canine congenital eye malformations, caused by an amino acid deletion (K12del) near the N terminus of retinol-binding protein (RBP4). The disease is only expressed when both dam and offspring are deletion homozygotes. RBP carries vitamin A (retinol) from hepatic stores to peripheral tissues, including the placenta and developing eye, where it is required to synthesize retinoic acid. Gestational vitamin A deficiency is a known risk factor for ocular birth defects. The K12del mutation disrupts RBP folding in vivo, decreasing its secretion from hepatocytes to serum. The maternal penetrance effect arises from an impairment in the sequential transfer of retinol across the placenta, via RBP encoded by maternal and fetal genomes. Our results demonstrate a mode of recessive maternal inheritance, with a physiological basis, and they extend previous observations on dominant-negative RBP4 alleles in humans.

[It is worthwhile to examine the optic disc]. / Näköhermon papillan tutkiminen.

Ophthalmoscopy is sometimes very difficult, especially if special ophthalmologic equipments are not available. However, the examination of the optic disc is a skill a general practitioner needs. The use of mydriatics makes it much easier. Examination of the optic disc head is essential when increased intracranial pressure is suspected. Diabetes and systemic hypertension are also diseases in which ophthalmoscopy is needed.