An atypical phenotype of macular and peripapillary retinal atrophy caused by a mutation in the RP2 gene.
OBJECTIVE
To determine the molecular basis and describe the phenotype of an atypical retinal dystrophy in a family presenting with bilateral, progressive central visual loss.


METHODS
Family members were examined. Investigations included Goldman perimetry, electrophysiology, and autofluorescence imaging. Candidate gene screening was performed using SSCP and sequence analysis. The proband's lymphoblastoid cells were examined for protein expression.


RESULTS
Fundal examination of the proband, his mother, and brother revealed peripapillary and macular atrophy. Autosomal dominant retinal dystrophy was suspected, but less severe disease in the mother led to screening for mutations in X linked genes. A 4 bp microdeletion in exon 3 of the RP2 gene, segregating with disease, was identified. No RP2 protein expression was detected.


CONCLUSIONS
The distinct phenotype in this family, caused by this frameshifting mutation in RP2, broadens the phenotypic spectrum of X linked retinitis pigmentosa. The absence of RP2 protein suggests that loss of protein function and not novel gain of function could account for the atypical phenotype. A definitive diagnosis of X linked retinitis pigmentosa permits appropriate genetic counselling with important implications for other family members. Clinicians should have a low threshold for screening RP2 in families with retinal dystrophy, including posterior retinal disease, not immediately suggestive of X linked inheritance.
Dandekar
S S
SS
Moorfields Eye Hospital, London, UK.
Ebenezer
N D
ND
Grayson
C
C
Chapple
J P
JP
Egan
C A
CA
Holder
G E
GE
Jenkins
S A
SA
Fitzke
F W
FW
Cheetham
M E
ME
Webster
A R
AR
Hardcastle
A J
AJ
D000328:Adult; D000368:Aged; D001284:Atrophy; D005136:Eye Proteins / Q000032:analysis / Q000235:genetics*; D005260:Female; D016368:Frameshift Mutation; D005654:Fundus Oculi; D019204:GTP-Binding Proteins; D017353:Gene Deletion; D006579:Heterozygote; D006801:Humans; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins; D008214:Lymphocytes / Q000737:chemistry; D008297:Male; D008565:Membrane Proteins; D008875:Middle Aged; D010375:Pedigree; D018807:Polymorphism, Single-Stranded Conformational; D012160:Retina / Q000473:pathology*; D012174:Retinitis Pigmentosa / Q000235:genetics* / Q000276:immunology / Q000473:pathology; D017422:Sequence Analysis, DNA; D014786:Vision Disorders / Q000235:genetics* / Q000276:immunology / Q000473:pathology
D005136:Eye Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C072178:RP2 protein, human; D019204:GTP-Binding Proteins