PAX6 MUTATION IN A LARGE BRAZILIAN FAMILY WITH CONGENITAL ANIRIDIA

FERNANDES-LIMA, ZS; ANDRADE, AKM; FERNANDES, AS; CORONADO, BNL; MONTE FILHO, HP; SANTOS, MJ; OMENA, RL; BIONDI, F; RAMALLO, V; HÜNEMEIER, T; PAIXÃO-CÔRTES VR; MONLLEO, L; SCHULER-FACCINI, L

Congreso; 59 Congresso Brasileiro de Genética; 2013

Congenital aniridia is a rare genetic disorder, with a wide range of clinical manifestations that include several degrees of iris hypoplasia associated with abnormalities of many other ocular structures and tissues. Usually diagnosed in early infancy, it eventually evolves to blindness in the adulthood. In about 2/3 of the cases this condition is inherited as an autosomal dominant trait, in the remaining 1/3 it occurs as a sporadic disorder by ?de novo? mutation. Despite the wide phenotype variability, more than 90% of the mutations identi ed are in the PAX6 (Paired box gene 6). PAX6 is a transcription factor of critical importance in the neurogenesis and oculogenesis processes.  e aim of this study was to investigate PAX6 mutations in a large Brazilian family with congenital aniridia. We identi ed 53 subjects across a 5-generation pedigree of a family of 163 individuals living in a rural area of the Northeast of Brazil (Água Branca, Alagoas). Diagnosis was established after complete ophthalmological examination. Biological samples were obtained for 35 (29 a ected and 6 controls) family members. Using speci c primers, DNA from 5 a ected and 2 controls were ampli ed by PCR for 18 regions covering all PAX6 gene exons, a total of 7527bp, for screening in search of the mutation.  e amplicons were puri ed, and sequenced in the ABI3730XL machine.  e chromatograms were aligned and their quality and accuracy were checked using the CodonCode Aligner software.  e 24 additional a ected and 4 familiar volunteers were subsequently evaluated for the presence of the possible causal mutation.  e Human Splicing Finder Version 2.4.1 software was used to predict the e ect of changing nucleotide found. All the 29 a ected individuals sequenced presented a heterozygous G>A change in the  rst nucleotide after 141 exon position (c.141+1G>A). All the 6 controls tested fr om this family didn?t show the mutation.  e identi ed mutation was described in PAX6 database (http://lsdb.hgu.mrc.ac.uk/home.php?select_db=PAX6). It possibly lead to disruption of one of the splice sites of exon 5, which contains part of the paired domain, altering the strength of the donor splice site. PAX6 mutations in splice sites were present in 8% of the case records.  e phenotype related varies from complete absence to mild iris defects. Splice site mutations modify or eliminate correct processing and maturation of the mRNA, and may or may not abolish the wild-type transcript expression completely, which could lead to variation in the phenotypes.  us, this mutation in the splice site could explain the phenotype variability found in this family.