ABCB6 mutations cause ocular coloboma.
Ocular coloboma is a developmental defect of the eye and is due to abnormal or incomplete closure of the optic fissure. This disorder displays genetic and clinical heterogeneity. Using a positional cloning approach, we identified a mutation in the ATP-binding cassette (ABC) transporter ABCB6 in a Chinese family affected by autosomal-dominant coloboma. The Leu811Val mutation was identified in seven affected members of the family and was absent in six unaffected members from three generations. A LOD score of 3.2 at θ = 0 was calculated for the mutation identified in this family. Sequence analysis was performed on the ABCB6 exons from 116 sporadic cases of microphthalmia with coloboma (MAC), isolated coloboma, and aniridia, and an additional mutation (A57T) was identified in three patients with MAC. These two mutations were not present in the ethnically matched control populations. Immunostaining of transiently transfected, Myc-tagged ABCB6 in retinal pigment epithelial (RPE) cells showed that it localized to the endoplasmic reticulum and Golgi apparatus of RPE cells. RT-PCR of ABCB6 mRNA in human cell lines and tissue indicated that ABCB6 is expressed in the retinae and RPE cells. Using zebrafish, we show that abcb6 is expressed in the eye and CNS. Morpholino knockdown of abcb6 in zebrafish produces a phenotype characteristic of coloboma and replicates the clinical phenotype observed in our index cases. The knockdown phenotype can be corrected with coinjection of the wild-type, but not mutant, ABCB6 mRNA, suggesting that the phenotypes observed in zebrafish are due to insufficient abcb6 function. Our results demonstrate that ABCB6 mutations cause ocular coloboma.
Department of Ophthalmology, Peking University Third Hospital, Beijing, China. wanglejin@hotmail.com
Lejin
L
Wang
Lejing
L
Wang
Fei
F
He
Juan
J
Bu
Yuanli
Y
Zhen
Xiaoqui
X
Liu
Xiaqi
X
Liu
Wei
W
Du
Jiamei
J
Dong
Jeffrey D
JD
Cooney
Sushil Kumar
SK
Dubey
Yi
Y
Shi
Bo
B
Gong
Jing
J
Li
Paul F
PF
McBride
Yanlei
Y
Jia
Fang
F
Lu
Kathleen A
KA
Soltis
Ying
Y
Lin
Prasanthi
P
Namburi
Chen
C
Liang
Periasamy
P
Sundaresan
Barry H
BH
Paw
Wei
W
Li
Dean Y
DY
Li
John D
JD
Phillips
Zhenglin
Z
Yang
D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis / Q000235:genetics*; D000818:Animals; D044466:Asian People / Q000235:genetics; D001483:Base Sequence; D002460:Cell Line; D002490:Central Nervous System / Q000378:metabolism; D003103:Coloboma / Q000235:genetics*; D005091:Exons; D005124:Eye Abnormalities / Q000235:genetics; D005260:Female; D006801:Humans; D008126:Lod Score; D008297:Male; D008850:Microphthalmos / Q000235:genetics; D008875:Middle Aged; D008969:Molecular Sequence Data; D060172:Morpholinos / Q000008:administration & dosage; D009154:Mutation; D055213:Retinal Pigment Epithelium; D014162:Transfection; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics
C107991:ABCB6 protein, human; D018528:ATP-Binding Cassette Transporters; D060172:Morpholinos; D029961:Zebrafish Proteins