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Congenital stationary night blindness (CSNB) can be inherited in an X-linked, autosomal dominant, or autosomal recessive pattern, depending on the genes involved. Two forms of CSNB can also affect horses, one linked to the leopard complex of equine coat colors and the other found in certain horse breeds. Both are autosomal recessives.
Congenital stationary night blindness (CSNB) is usually diagnosed based on the owner's observations, but some horses have visibly abnormal eyes: poorly aligned eyes (dorsomedial strabismus) or involuntary eye movement (nystagmus). [8] In horses, CSNB has been linked with the leopard complex color pattern since the 1970s. [9]
Congenital stationary night blindness has been linked with the leopard complex since the 1970s. [14] The presence of CSNB in non-leopard breeds and horses suggested that the two conditions might be located on close, but separate genes.
Homozygous leopards are substantially more prone to congenital stationary night blindness. [9] Congenital stationary night blindness is present at birth and is characterized by impaired vision in dark conditions.
One result of the mapping of the horse genome was locating the mutation that creates the Leopard complex (Lp) spotting pattern seen in breeds such as the Appaloosa. [2] Horses homozygous for the Lp gene are also at risk for congenital stationary night blindness (CSNB). [6]
Mutations in this gene cause congenital stationary night blindness in humans (CSNB). [8] which is a stable retinal disorder. [2] The consequence of this mutation results in an abnormal night vision. Nyctalopin is critical due to the fact that it generates a depolarizing bipolar cell response due to the mutation on the NYX gene. [6]
Congenital blindness is sometimes used interchangeably with "Childhood Blindness." However, current literature has various definitions of both terms. Childhood blindness encompasses multiple diseases and conditions present in ages up to 16 years old, which can result in permanent blindness or severe visual impairment over time. [ 2 ]
Horses heterozygous for the Ile118Lys mutation on the equine EDNRB gene—carriers of lethal white syndrome—usually exhibit a white-spotting pattern called "frame", or "frame overo". [5] [7] [9] [13] Frame is characterized by jagged, sharply defined, horizontally oriented white patches that run along the horse's neck, shoulder, flank, and ...