A homozygous splice mutation in the HSF4 gene is associated with an autosomal recessive congenital cataract.
OBJECTIVE
To map the locus and identify the gene causing autosomal recessive congenital cataracts in a large consanguineous Tunisian family.


METHODS
DNA was extracted from blood samples from a large Tunisian family with an autosomal recessive, congenital, total white cataract. A genome-wide scan was performed with microsatellite markers. All exons and the splice sites of the HSF4 gene were sequenced in all members of the Tunisian family and in control individuals. RT-PCR was used to detect different transcripts of the HSF4 gene in the human lens. The transcripts were cloned in a TA cloning vector and sequenced.


RESULTS
Two-point linkage analyses showed linkage to markers on 16q22 with a maximum lod score of 17.78 at theta = 0.01 with D16S3043. Haplotype analysis refined the critical region to a 1.8-cM (4.8-Mb) interval, flanked by D16S3031 and D16S3095. This region contains HSF4, some mutations of which cause the autosomal dominant Marner cataract. Sequencing of HSF4 showed a homozygous mutation in the 5' splice site of intron 12 (c.1327+4A-->G), which causes the skipping of exon 12. A more detailed study of the transcripts resulting from alternative splicing of the HSF4 gene in the lens is also reported, showing the major transcript HSF4b.


CONCLUSIONS
This is the first report describing association of an autosomal recessive cataract with the HSF4 locus on 16q21-q22.1 and the first description of HSF4 splice variants in the lens showing that HSF4b is the major transcript.
Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Nizar
N
Smaoui
Omar
O
Beltaief
Sonia
S
BenHamed
Ridha
R
M'Rad
Faouzi
F
Maazoul
Amel
A
Ouertani
Habiba
H
Chaabouni
J Fielding
JF
Hejtmancik
D002386:Cataract / Q000151:congenital / Q000235:genetics*; D002874:Chromosome Mapping; D002885:Chromosomes, Human, Pair 16 / Q000235:genetics*; D003241:Consanguinity; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics*; D005260:Female; D005808:Genes, Recessive; D006239:Haplotypes; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins / Q000235:genetics; D006801:Humans; D007438:Introns / Q000235:genetics; D008126:Lod Score; D008297:Male; D018895:Microsatellite Repeats; D009154:Mutation; D010375:Pedigree; D022821:RNA Splice Sites / Q000235:genetics*; D012326:RNA Splicing / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics*; D014416:Tunisia
D004268:DNA-Binding Proteins; C102948:HSF4 protein, human; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D022821:RNA Splice Sites; D012333:RNA, Messenger; D014157:Transcription Factors