Identification of three novel OA1 gene mutations identified in three families misdiagnosed with congenital nystagmus and carrier status determination by real-time quantitative PCR assay.
BACKGROUND
X-linked ocular albinism type 1 (OA1) is caused by mutations in OA1 gene, which encodes a membrane glycoprotein localised to melanosomes. OA1 mainly affects pigment production in the eye, resulting in optic changes associated with albinism including hypopigmentation of the retina, nystagmus, strabismus, foveal hypoplasia, abnormal crossing of the optic fibers and reduced visual acuity. Affected Caucasian males usually appear to have normal skin and hair pigment.


RESULTS
We identified three previously undescribed mutations consisting of two intragenic deletions (one encompassing exon 6, the other encompassing exons 7-8), and a point mutation (310delG) in exon 2. We report the development of a new method for diagnosis of heterozygous deletions in OA1 gene based on measurement of gene copy number using real-time quantitative PCR from genomic DNA.


CONCLUSIONS
The identification of OA1 mutations in families earlier reported as families with hereditary nystagmus indicate that ocular albinism type 1 is probably underdiagnosed. Our method of real-time quantitative PCR of OA1 exons with DMD exon as external standard performed on the LightCycler trade mark allows quick and accurate carrier-status assessment for at-risk females.
Faugère
Valérie
V
Laboratoire de Génétique Moléculaire, Institut Universitaire de Recherche Clinique IURC et CHU, 641 Avenue du Doyen Gaston Giraud, 34093 Montpellier cedex 5, France. vfaugere@igh.cnrs.fr
Tuffery-Giraud
Sylvie
S
Hamel
Christian
C
Claustres
Mireille
M
D000328:Adult; D016117:Albinism, Ocular / Q000175:diagnosis / Q000235:genetics*; D002648:Child; D041321:Chromosomes, Human, X / Q000235:genetics; D003199:Computer Systems; D003951:Diagnostic Errors; D005091:Exons / Q000235:genetics; D005136:Eye Proteins / Q000235:genetics*; D005260:Female; D018628:Gene Dosage; D006580:Genetic Carrier Screening / Q000379:methods; D005819:Genetic Markers / Q000235:genetics; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D020417:Nystagmus, Congenital / Q000175:diagnosis*; D010375:Pedigree; D016133:Polymerase Chain Reaction / Q000379:methods*
D005136:Eye Proteins; C095276:GPR143 protein, human; D005819:Genetic Markers; D008562:Membrane Glycoproteins