A mutation in the FOXE3 gene causes congenital primary aphakia in an autosomal recessive consanguineous Pakistani family.
OBJECTIVE
Aphakia is the complete absence of any lens in the eye, either due to surgical removal of the lens as a result of a perforating wound or ulcer, or due to a congenital anomaly. The purpose of this study was to elucidate the molecular genetics for a large consanguineous Pakistani family with a clear aphakia phenotype.


METHODS
The initial homozygosity screening of the family was extended to all the known autosomal recessive cataract loci in order to exclude the possibility of surgical cataract removal leading to aphakia. The screening was performed using polymorphic nucleotide repeat markers, followed by DNA sequencing of a possible candidate gene, the forkhead box protein E3 gene (FOXE3). The identified mutation was counter-checked by a diagnostic restriction enzyme digest of all the family members, and an analysis of the normal population.


RESULTS
The initial homozygosity screening of 13 known autosomal recessive loci resulted in negative LOD (logarithm of odds) scores. The aphakia phenotype suggested a mutation in FOXE3 close to the AR-locus 1p34.3-p32.2, and sequence analyses revealed the nonsense mutation c.720C>A, changing cysteine 240 to a stop codon. Segregation in the family was shown by diagnostic restriction enzyme digest, and marker analysis of another aphakia family from Madagascar carrying the same mutation excluded the presence of a founder mutation. Clinical re-examination of the family was not possible due to the escalating security concerns and internal displacement of the population in this region of Pakistan which has prevailed for many months.


CONCLUSIONS
FOXE3 is responsible for the early developmental arrest of the lens placode, and the complete loss of a functional FOXE3 protein results in primary aphakia. It can also be deduced that this mutation is quite primitive in origin since the same mutation is responsible for the same phenotypic outcome in two families of geographically different descent.
Anjum
Iram
I
Human Molecular Genetics Laboratory, Health Biotechnology Division, National Institute for Biotechnology & Genetic Engineering (NIBGE), Faisalabad, Pakistan.
Eiberg
Hans
H
Baig
Shahid Mahmood
SM
Tommerup
Niels
N
Hansen
Lars
L
D000595:Amino Acid Sequence; D001035:Aphakia / Q000151:congenital* / Q000235:genetics*; D001483:Base Sequence; D002386:Cataract / Q000235:genetics; D003241:Consanguinity; D004252:DNA Mutational Analysis; D005190:Family; D005260:Female; D051858:Forkhead Transcription Factors / Q000737:chemistry / Q000235:genetics*; D005808:Genes, Recessive / Q000235:genetics*; D056426:Genetic Loci / Q000235:genetics; D006239:Haplotypes / Q000235:genetics; D006720:Homozygote; D006801:Humans; D008126:Lod Score; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D010154:Pakistan; D010375:Pedigree; D020161:Physical Chromosome Mapping
C404285:FOXE3 protein, human; D051858:Forkhead Transcription Factors