Supporting people with aniridia and their Families
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Pax6 the Aniridia GeneAll cases of aniridia are genetic and about 98% of these are caused by a mutation of the PAX6 gene, which is found on band 13 on the short arm of the 11th chromosome (11p13). This gene is responsible for the development of the eye, brain and nasal tissue. A mutation of this gene causes haploinsufficiency, the gene is unable to function. heterozygoteWhen a child is born with a mutation in one of the two PAX6 genes, the most significant clinical findings are the underdevelopment of the eye. The most common phenotype is aniridia this is usually caused by a nonsense mutation. Very few missense mutations are reported in PAX6 but those that have been reported tended to lead to to mild or atypical aniridia phenotypes or to other eye diseases such as congential nystagmus, isolated foveal hypoplasia and peters' anomaly. these missense mutations tend to be found in the Paired Domain. a low penitrence mutation was recently found in the Home Damain for the PAX6 gene in a child with isolated Iris coloboma. New research is being conducted into the affect of PAX 6 on the brain. recent studies have shown hypoplastic olfactory bulbs causing mild or moderate hyposmia (poor sense of smell) Absent pineal gland - the pineal gland produces the hormone melatnin responible for sleep response Unilateral polymicrogyria. a malformation of the cerebral cortex (outer layer of the brain). The term polymicrogyria designates an excessive number of small and prominent convolutions spaced out by shallow and enlarged sulci (grooves), pancreatic malfunction - This causes glucose intolerance with one reported case of diabetes in a family with aniridia. homozygoteWhen a child is born with two pax6 mutations have serve craniolfacial abnormalities, nerves system defects which are lethal. Glaser et al describe the first known case. The head was small with disproportionately large ears. The eyes where absent The nose was malformed with a flattened bridge and pinpoint external nares, and choanal atresia (lack of a connection between the nose and the mouth. babies are naturally nose breathers but in this condition cannot breath through their nose causing resperatary distress). The brain was small and misshapen. The cerebral hemispheres were thin and widely separated with a single open ventricular system. In 2% of aniridia cases are part of a condition called Gillespie syndrome/. Mutations in the PAX6 gene are not found in people with condition. Links |