Anterior segment mesenchymal dysgenesis in a large Australian family is associated with the recurrent 17 bp duplication in PITX3.
OBJECTIVE
A recurrent 17 bp duplication (c.657ins17bp) of a segment of the paired-like homeodomain transcription factor 3 (PITX3) gene on human chromosome 10 has been reported in seven families with autosomal dominant posterior polar cataracts with or without anterior segment mesenchymal dysgenesis (ASMD). ASMD can include Peters anomaly with corneal clouding, iridolenticular corneal adhesions, displaced Schwalbe's line, and cataract as described previously in a large Australian family. This study reports the examination of PITX3 in this Australian family.


METHODS
Clinical examinations of the proband and her relatives were performed as part of routine follow up. A polymerase chain reaction (PCR) based test for the duplication in PITX3 was developed, and DNA from 21 members of the proband's family was tested.


RESULTS
All clinically affected members of the family had the same 17 bp duplication of PITX3. There was no difference in the size of the duplication between the severely affected individuals and the more mildly affected individuals. Prenatal diagnosis was performed for two offspring of one affected person. In the first pregnancy, the fetus was shown to carry the duplication while in the second pregnancy, the fetus was shown to be homozygous for the normal allele.


CONCLUSIONS
The results show that in some individuals within one family, duplication of this segment of PITX3 can result in severe symptoms leading to functional blindness while in other individuals in the same family or in other families, the same duplication leads to treatable cataract with minimal visual impairment.
Summers
Kim M
KM
Roslin Institute, University of Edinburgh, Roslin, Midlothian, UK. kim.summers@roslin.ed.ac.uk
Withers
Stephen J
SJ
Gole
Glen A
GA
Piras
Sara
S
Taylor
Peter J
PJ
D000869:Anterior Eye Segment / Q000002:abnormalities*; D001315:Australia; D020029:Base Pairing / Q000235:genetics*; D001483:Base Sequence; D002648:Child; D005091:Exons / Q000235:genetics; D005190:Family; D005260:Female; D020440:Gene Duplication; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D008297:Male; D008648:Mesoderm / Q000002:abnormalities*; D008969:Molecular Sequence Data; D010375:Pedigree; D011247:Pregnancy; D011296:Prenatal Diagnosis; D014157:Transcription Factors / Q000235:genetics*
D018398:Homeodomain Proteins; D014157:Transcription Factors; C433629:homeobox protein PITX3