1
|
Nieves-Moreno M, Noval S, Peralta J, Palomares-Bralo M, del Pozo A, Garcia-Miñaur S, Santos-Simarro F, Vallespin E. Expanding the Phenotypic Spectrum of PAX6 Mutations: From Congenital Cataracts to Nystagmus. Genes (Basel) 2021; 12:genes12050707. [PMID: 34065151 PMCID: PMC8151272 DOI: 10.3390/genes12050707] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Revised: 05/04/2021] [Accepted: 05/05/2021] [Indexed: 12/15/2022] Open
Abstract
Background: Congenital aniridia is a complex ocular disorder, usually associated with severe visual impairment, generally caused by mutations on the PAX6 gene. The clinical phenotype of PAX6 mutations is highly variable, making the genotype–phenotype correlations difficult to establish. Methods: we describe the phenotype of eight patients from seven unrelated families with confirmed mutations in PAX6, and very different clinical manifestations. Results: Only two patients had the classical aniridia phenotype while the other two presented with aniridia-related manifestations, such as aniridia-related keratopathy or partial aniridia. Congenital cataracts were the main manifestation in three of the patients in this series. All the patients had nystagmus and low visual acuity. Conclusions: The diagnosis of mild forms of aniridia is challenging, but these patients have a potentially blinding hereditary disease that might present with a more severe phenotype in future generations. Clinicians should be aware of the mild aniridia phenotype and request genetic testing to perform an accurate diagnosis.
Collapse
Affiliation(s)
- Maria Nieves-Moreno
- Department of Ophthalmology, Hospital Universitario La Paz, 28046 Madrid, Spain; (S.N.); (J.P.)
- Correspondence:
| | - Susana Noval
- Department of Ophthalmology, Hospital Universitario La Paz, 28046 Madrid, Spain; (S.N.); (J.P.)
| | - Jesus Peralta
- Department of Ophthalmology, Hospital Universitario La Paz, 28046 Madrid, Spain; (S.N.); (J.P.)
| | - María Palomares-Bralo
- Department of Molecular Developmental Disorders, Medical and Molecular Genetics Institue (INGEMM) IdiPaz, CIBERER, Hospital Universitario La Paz, 28046 Madrid, Spain;
| | - Angela del Pozo
- Department of Bioinformatics, Medical and Molecular Genetics Institue (INGEMM) IdiPaz, CIBERER, Hospital Universitario La Paz, 28046 Madrid, Spain;
| | - Sixto Garcia-Miñaur
- Department of Clinical Genetics, Medical and Molecular Genetics Institue (INGEMM) IdiPaz, CIBERER, Hospital Universitario La Paz, 28046 Madrid, Spain; (S.G.-M.); (F.S.-S.)
| | - Fernando Santos-Simarro
- Department of Clinical Genetics, Medical and Molecular Genetics Institue (INGEMM) IdiPaz, CIBERER, Hospital Universitario La Paz, 28046 Madrid, Spain; (S.G.-M.); (F.S.-S.)
| | - Elena Vallespin
- Department of Molecular Ophthalmology, Medical and Molecular Genetics Institue (INGEMM) IdiPaz, CIBERER, Hospital Universitario La Paz, 28046 Madrid, Spain;
| |
Collapse
|
2
|
Jafari R, Ahmadzadeh Amiri A. A Clinical and Genetic Review of Aniridia. JOURNAL OF PEDIATRICS REVIEW 2015. [DOI: 10.17795/jpr-241] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
|
3
|
Chang JW, Kim JH, Kim SJ, Yu YS. Congenital aniridia: long-term clinical course, visual outcome, and prognostic factors. KOREAN JOURNAL OF OPHTHALMOLOGY 2014; 28:479-85. [PMID: 25435751 PMCID: PMC4239467 DOI: 10.3341/kjo.2014.28.6.479] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Accepted: 03/13/2014] [Indexed: 11/23/2022] Open
Abstract
Purpose To describe the clinical course of congenital aniridia and to evaluate prognostic factors for visual outcome after long-term follow-up. Methods The medical records of 120 eyes from 60 patients with congenital aniridia were retrospectively reviewed. The prevalence and clinical course of ophthalmic characteristics, systemic disease, refractive errors, and visual acuity were assessed. Prognostic factors for final visual outcomes were analyzed. Results Aniridic keratopathy developed in 82 (69%) of 119 eyes. Macular hypoplasia was observed in 70 eyes of 35 patients (91%). Cataract was observed in 63 of 120 eyes (53%). Nystagmus was present in 41 patients (68% of 60 patients) at the initial visit but decreased in five patients (8% of 60 patients). Ocular hypertension was detected in 19 eyes (20% of 93 eyes), six (32% of 19 eyes) of which developed secondarily after cataract surgery. The mean changes in spherical equivalent and astigmatism during the follow-up period were -1.10 and 1.53 diopter, respectively. The mean final visual acuity was 1.028 logarithm of minimal angle of resolution. Nystagmus and ocular hypertension were identified as prognostic factors for poor visual outcome. Conclusions Identification of nystagmus and ocular hypertension was important to predict final visual outcome. Based on the high rate of secondary ocular hypertension after cataract surgery, careful management is needed.
Collapse
Affiliation(s)
- Ji Woong Chang
- Department of Ophthalmology, Ilsan Paik Hospital, Inje University College of Medicine, Goyang, Korea
| | - Jeong Hun Kim
- Department of Ophthalmology, Seoul National University Hospital, Seoul, Korea. ; Seoul Artificial Eye Center, Seoul National University Hospital Clinical Research Institute, Seoul, Korea
| | - Seong-Joon Kim
- Department of Ophthalmology, Seoul National University Hospital, Seoul, Korea. ; Seoul Artificial Eye Center, Seoul National University Hospital Clinical Research Institute, Seoul, Korea
| | - Young Suk Yu
- Department of Ophthalmology, Seoul National University Hospital, Seoul, Korea. ; Seoul Artificial Eye Center, Seoul National University Hospital Clinical Research Institute, Seoul, Korea
| |
Collapse
|
4
|
Ma ZL, Wang G, Cheng X, Chuai M, Kurihara H, Lee KKH, Yang X. Excess caffeine exposure impairs eye development during chick embryogenesis. J Cell Mol Med 2014; 18:1134-43. [PMID: 24636305 PMCID: PMC4508153 DOI: 10.1111/jcmm.12260] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2013] [Accepted: 01/22/2014] [Indexed: 12/17/2022] Open
Abstract
Caffeine has been an integral component of our diet and medicines for centuries. It is now known that over consumption of caffeine has detrimental effects on our health, and also disrupts normal foetal development in pregnant mothers. In this study, we investigated the potential teratogenic effect of caffeine over-exposure on eye development in the early chick embryo. Firstly, we demonstrated that caffeine exposure caused chick embryos to develop asymmetrical microphthalmia and induced the orbital bone to develop abnormally. Secondly, caffeine exposure perturbed Pax6 expression in the retina of the developing eye. In addition, it perturbed the migration of HNK-1+ cranial neural crest cells. Pax6 is an important gene that regulates eye development, so altering the expression of this gene might be the cause for the abnormal eye development. Thirdly, we found that reactive oxygen species (ROS) production was significantly increased in eye tissues following caffeine treatment, and that the addition of anti-oxidant vitamin C could rescue the eyes from developing abnormally in the presence of caffeine. This suggests that excess ROS induced by caffeine is one of the mechanisms involved in the teratogenic alterations observed in the eye during embryogenesis. In sum, our experiments in the chick embryo demonstrated that caffeine is a potential teratogen. It causes asymmetrical microphthalmia to develop by increasing ROS production and perturbs Pax6 expression.
Collapse
Affiliation(s)
- Zheng-Lai Ma
- Department of Histology & Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Institute of Fetal-Preterm Labor Medicine, Medical College of Jinan University, Guangzhou, China
| | | | | | | | | | | | | |
Collapse
|
5
|
Adaptation of the central retina for high acuity vision: cones, the fovea and the avascular zone. Prog Retin Eye Res 2013; 35:63-81. [PMID: 23500068 DOI: 10.1016/j.preteyeres.2013.01.005] [Citation(s) in RCA: 169] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 01/25/2013] [Accepted: 01/25/2013] [Indexed: 12/31/2022]
Abstract
Presence of a fovea centralis is directly linked to molecular specification of an avascular area in central retina, before the fovea (or 'pit') begins to form. Modelling suggests that mechanical forces, generated within the eye, initiate formation of a pit within the avascular area, and its later remodelling in the postnatal period. Within the avascular area the retina is dominated by 'midget' circuitry, in which signals are transferred from a single cone to a single bipolar cell, then a single ganglion cell. Thus in inner, central retina there are relatively few lateral connections between neurons. This renders the region adaptable to tangential forces, that translocate of ganglion cells laterally/centrifugally, to form the fovea. Optical coherence tomography enables live imaging of the retina, and shows that there is greater variation in the morphology of foveae in humans than previously thought. This variation is associated with differences in size of the avascular area and appears to be genetically based, but can be modified by environmental factors, including prematurity. Even when the fovea is absent (foveal hypoplasia), cones in central retina adopt an elongated and narrow morphology, enabling them to pack more densely to increase the sampling rate, and to act as more effective waveguides. Given these findings, what then is the adaptive advantage of a fovea? We suggest that the advantages of having a pit in central retina are relatively few, and minor, but together work to enhance acuity.
Collapse
|
6
|
Reply to Aniridia—To Be or Not To Be? Transplantation 2010. [DOI: 10.1097/tp.0b013e3181c832a8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
7
|
Hewitt AW, Kearns LS, Jamieson RV, Williamson KA, van Heyningen V, Mackey DA. PAX6Mutations May Be Associated with High Myopia. Ophthalmic Genet 2009; 28:179-82. [PMID: 17896318 DOI: 10.1080/13816810701356676] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
PAX6 is a key regulator of eye development and there are many well recognized ophthalmic sequelae of mutations at this locus. The 14 exon PAX6 gene is well conserved across species and phyla. Coding region mutations manifest in a variety of phenotypes. Predicted premature protein truncations are generally associated with classical aniridia. Missense mutations are often found in cases with variant phenotypes such as ectopia pupillae; isolated foveal hypoplasia; nystagmus and hyaloid vessel proliferation. The locus has also been implicated, through a genome-wide sib-pair scan, to be important in the normal variation of myopia. We investigated the association between identified PAX6 mutations and refractive error in Australian patients from four pedigrees. Two of eight subjects with a 1410delC PAX6 mutation had a mean spherical equivalence < -9D, whilst a mean spherical equivalence < or = -5D was recorded in two from four subjects with an Arg240Stop PAX6 mutation and one of two subjects with a Glu93Stop mutation. One individual identified with a Pro346Ala PAX6 mutation had a mean spherical equivalence of +2.8 D. Thus, our observations generally support other incidental findings, that PAX6 mutation, particularly predicted haploinsufficiency, may be associated with extreme refractive error, although the mechanism by which this occurs is not clear.
Collapse
Affiliation(s)
- Alex W Hewitt
- Department of Ophthalmology, Flinders University, Adelaide, Australia
| | | | | | | | | | | |
Collapse
|
8
|
Kawano T, Wang C, Hotta Y, Sato M, Iwata-Amano E, Hikoya A, Fujita N, Koyama N, Shirai S, Azuma N, Ohtsubo M, Shimizu N, Minoshima S. Three novel mutations of the PAX6 gene in Japanese aniridia patients. J Hum Genet 2007; 52:571-574. [PMID: 17568989 DOI: 10.1007/s10038-007-0153-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2007] [Accepted: 04/17/2007] [Indexed: 10/23/2022]
Abstract
Mutations in the PAX6 gene of Japanese aniridia patients were analyzed. Four types of mutations including one known (474delC) and three novel (786_787ins10, 678_688del11 and 572_575delAATCins14) were found in six patients from four families. A patient with the mutation 572_575delAATCins14 also manifested VATER association. This is the first case of aniridia accompanied by VATER association. All of mutations found in this study are frameshift type, resulting in premature termination of translation. The database for PAX6 gene mutation has been made using a graphical data display system MutationView ( http://mutview.dmb.med.keio.ac.jp/ ).
Collapse
Affiliation(s)
- Toshio Kawano
- Department of Ophthalmology, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Chunxia Wang
- Department of Ophthalmology, Hamamatsu University School of Medicine, Hamamatsu, Japan
- Medical Photobiology Department, Photon Medical Research Center, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu, 431-3192, Japan
| | - Yoshihiro Hotta
- Department of Ophthalmology, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Miho Sato
- Department of Ophthalmology, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Emi Iwata-Amano
- Department of Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Akiko Hikoya
- Department of Ophthalmology, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Naoya Fujita
- Department of Pediatrics, Toyohashi Municipal Hospital, Toyohashi, Japan
| | - Norihisa Koyama
- Department of Pediatrics, Toyohashi Municipal Hospital, Toyohashi, Japan
| | - Shoichiro Shirai
- Department of Ophthalmology, Toyohashi Municipal Hospital, Toyohashi, Japan
| | - Noriyuki Azuma
- Department of Ophthalmology, National Center for Child Health and Development, Tokyo, Japan
| | - Masafumi Ohtsubo
- Medical Photobiology Department, Photon Medical Research Center, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu, 431-3192, Japan
| | - Nobuyoshi Shimizu
- Department of Molecular Biology, Keio University School of Medicine, Tokyo, Japan
| | - Shinsei Minoshima
- Medical Photobiology Department, Photon Medical Research Center, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu, 431-3192, Japan.
| |
Collapse
|
9
|
Willcock C, Grigg J, Wilson M, Tam P, Billson F, Jamieson R. Congenital iris ectropion as an indicator of variant aniridia. Br J Ophthalmol 2006; 90:658-569. [PMID: 16622108 PMCID: PMC1857026 DOI: 10.1136/bjo.2005.089698] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
|
10
|
Vincent MC, Gallai R, Olivier D, Speeg-Schatz C, Flament J, Calvas P, Dollfus H. Variable phenotype related to a novel PAX 6 mutation (IVS4+5G>C) in a family presenting congenital nystagmus and foveal hypoplasia. Am J Ophthalmol 2004; 138:1016-21. [PMID: 15629294 DOI: 10.1016/j.ajo.2004.08.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/02/2004] [Indexed: 11/25/2022]
Abstract
PURPOSE Several ocular defects have been identified as a consequence of the PAX6 gene mutations. With regard to the implication of this gene in unusual phenotypes, we report a family presenting with congenital nystagmus, foveal hypoplasia, and iris hypoplasia or atypical coloboma. DESIGN Observational case report. METHODS The entire transcribed region of the PAX6 gene was submitted to mutation search at the DNA and mRNA levels in five affected members of a French family in test with 82 normal subjects. RESULTS A novel heterozygous PAX6 gene splice mutation (IVS4 + 5G>C) was identified. The mutation is located in IVS4 within the consensus donor splice site. A mutant mRNA lacking exon 4 as the sole defect was evidenced. The resultant protein was predicted to contain a cryptic ATG initiation codon in exon 3 and a slightly altered paired-domain in an open reading frame extended by 13 amino acids. CONCLUSIONS The association of anterior segment anomalies and foveal hypoplasia with one of the slightest alterations of the PAX6 protein described to date confirms the association of variant phenotypes with hypomorphic alleles. Mutation screening of the PAX6 gene could be useful in elucidating the origin of complex ocular malformations.
Collapse
|
11
|
Neethirajan G, Krishnadas SR, Vijayalakshmi P, Shashikant S, Sundaresan P. PAX6 gene variations associated with aniridia in south India. BMC MEDICAL GENETICS 2004; 5:9. [PMID: 15086958 PMCID: PMC419353 DOI: 10.1186/1471-2350-5-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/05/2003] [Accepted: 04/16/2004] [Indexed: 11/10/2022]
Abstract
Background Mutations in the transcription factor gene PAX6 have been shown to be the cause of the aniridia phenotype. The purpose of this study was to analyze patients with aniridia to uncover PAX6 gene mutations in south Indian population. Methods Total genomic DNA was isolated from peripheral blood of twenty-eight members of six clinically diagnosed aniridia families and 60 normal healthy controls. The coding exons of the human PAX6 gene were amplified by PCR and allele specific variations were detected by single strand conformation polymorphism (SSCP) followed by automated sequencing. Results The sequencing results revealed novel PAX6 mutations in three patients with sporadic aniridia: c.715ins5, [c.1201delA; c.1239A>G] and c.901delA. Two previously reported nonsense mutations were also found: c.482C>A, c.830G>A. A neutral polymorphism was detected (IVS9-12C>T) at the boundary of intron 9 and exon 10. The two nonsense mutations found in the coding region of human PAX6 gene are reported for the first time in the south Indian population. Conclusion The genetic analysis confirms that haploinsuffiency of the PAX6 gene causes the classic aniridia phenotype. Most of the point mutations detected in our study results in stop codons. Here we add three novel PAX6 gene mutations in south Indian population to the existing spectrum of mutations, which is not a well-studied ethnic group. Our study supports the hypothesis that a mutation in the PAX6 gene correlates with expression of aniridia.
Collapse
Affiliation(s)
| | | | | | - Shetty Shashikant
- Department of Pediatric Ophthalmology and Strabismus, Aravind Eye Hospital, Madurai, India
| | | |
Collapse
|
12
|
De Becker I, Walter M, Noël LP. Phenotypic variations in patients with a 1630 A>T point mutation in the PAX6 gene. Can J Ophthalmol 2004; 39:272-8. [PMID: 15180145 DOI: 10.1016/s0008-4182(04)80125-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
BACKGROUND The extreme clinical case-to-case variability of aniridia, even within families, can cause difficulties in making the correct diagnosis, prognosis and treatment plan. We describe seven patients from two families demonstrating variable expression of this syndrome, all with the same single point mutation within the PAX6 gene. METHODS Case presentations. The authors review the clinical ophthalmic findings of the aniridia-keratopathy syndrome from two families, one involving four generations, the other with two generations. Polymerase chain reaction amplification of all 14 exons of the PAX6 gene was performed for five patients. RESULTS The iris findings varied from classic total absence to nearly normal iris appearance. Corneal changes were minimal in the younger patients but vision-impairing in the older. None of the patients had glaucoma. The five patients who underwent DNA analysis shared the same PAX6 point mutation defect (1630A>T). INTERPRETATION Bilateral corneal changes progressing from mild opacification at the limbus to vascularized central keratopathy, especially in the presence of nystagmus, are highly suggestive of a PAX6 mutation. Such patients may theoretically benefit from early limbal stem cell replacement therapy.
Collapse
Affiliation(s)
- Inge De Becker
- Department of Ophthalmology, Dalhousie University, Halifax, NS
| | | | | |
Collapse
|
13
|
Ylikärppä R, Eklund L, Sormunen R, Kontiola AI, Utriainen A, Määttä M, Fukai N, Olsen BR, Pihlajaniemi T. Lack of type XVIII collagen results in anterior ocular defects. FASEB J 2003; 17:2257-9. [PMID: 14525950 DOI: 10.1096/fj.02-1001fje] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Mice lacking type XVIII collagen have defects in the posterior part of the eye, including delayed regression of the hyaloid vasculature and poor outgrowth of the retinal vessels. We report here that these mice also have a fragile iris and develop atrophy of the ciliary body. The irises of Col18a1-/- mice can be seen to adhere to the lens and cornea. After the pupils begin to function, the double layer of epithelial cells separates at the apical cell contacts, leading to defoliation of its posterior pigment epithelial cell layer, and extracellular material begins to accumulate in the basement membrane zones of the iris. In contrast to the iris epithelia, where no clear signs of cellular atrophy were detected, the lack of type XVIII collagen resulted in atrophy of the pigmented epithelial cells of the ciliary body, and there were also ultrastructural abnormalities in the basement membrane zones. These changes did not lead to chronically elevated intraocular pressures, however. Our results indicate that type XVIII collagen is needed for the integrity of the epithelial basement membranes of the iris and the ciliary body and that its gene should therefore be taken into account as a new potential cause of anterior segment disorders in the eye.
Collapse
Affiliation(s)
- Ritva Ylikärppä
- Collagen Research Unit, Biocenter Oulu and Department of Medical Biochemistry and Molecular Biology, University of Oulu, Finland
| | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Vincent MC, Pujo AL, Olivier D, Calvas P. Screening for PAX6 gene mutations is consistent with haploinsufficiency as the main mechanism leading to various ocular defects. Eur J Hum Genet 2003; 11:163-9. [PMID: 12634864 DOI: 10.1038/sj.ejhg.5200940] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2002] [Revised: 11/21/2002] [Accepted: 11/27/2002] [Indexed: 11/08/2022] Open
Abstract
PAX6, a paired box transcriptional factor, is considered as the master control gene for morphogenesis of the eye. Human PAX6 mutations have been associated with a range of eye abnormalities, including aniridia, various anterior segment defects and foveal hypoplasia. We carried out a mutational analysis of the PAX6 gene in 54 unrelated patients with aniridia or related syndromes. A deleterious variation was evidenced in 17 sporadic cases (50%) and in 13 (72%) familial cases. Twenty-four different mutations, 17 of which are novel, were found. The spectrum of PAX6 mutations was highly homogeneous: 23 mutations (96%) leading to premature stop codons (eight nonsense and four splice site mutations, 11 insertions and deletions) and only one (4%) missense mutation. Twenty-two mutations were associated with aniridia phenotypes whereas two were associated with atypical phenotypes. These latter encompassed a missense mutation (R19P) in an individual with a microphthalmia-sclerocornea and a splice site mutation (IVS4+5G > C) in a family presenting with a congenital nystagmus. Both represented the most probably hypomorphic alleles. Aniridia cases were associated with nonsense or frameshifting mutations. A careful examination of the phenotypes did not make it possible to recognise significant differences whenever the predicted protein was deprived of one or another of its functional domains. This strongly suggested that most of the truncating mutations generated null alleles by nonsense mediated mRNA decay. Our observations support the concept of dosage effects of the PAX6 mutations as well as presenting evidence for variable expressivity.
Collapse
Affiliation(s)
- Marie-Claire Vincent
- Service de Génétique Médicale, Hôpital Purpan, Pavillon Lefebvre, 1, place Baylac, 31059 Toulouse cedex, France
| | | | | | | |
Collapse
|
15
|
Mishra R, Gorlov IP, Chao LY, Singh S, Saunders GF. PAX6, paired domain influences sequence recognition by the homeodomain. J Biol Chem 2002; 277:49488-94. [PMID: 12388550 DOI: 10.1074/jbc.m206478200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PAX6 functions as a transcription factor and has two DNA-binding domains, a paired domain (PD) and a homeodomain (HD), joined by a glycine-rich linker and followed by a proline-serine-threonine-rich (PST) transactivation region at the C terminus. The mechanism of PAX6 function is not clearly understood, and few target genes in vertebrates have been identified. In this report we described the functional analyses of patient missense mutations from the paired domain region of PAX6 and a paireddomain-less isoform (PD-less) of Pax6 that lacks the paired domain and part of the glycine-rich linker. The PD-less was expressed in the brain, eyes, and pancreas of mouse. The level of expression of this isoform was relatively higher in brain. The mutation sites PAX6-L46R and -C52R were located in the PD of PAX6 on either end of the 5a-polypeptide insert of the alternatively spliced form of PAX6, PAX6-5a. Another PAX6 mutant V53L described in this report was adjacent to C52R. We created corresponding mutations in PAX6 and PAX6-5a, and evaluated their transcriptional activation and DNA binding properties. The PD mutants of PAX6 (L46R, C52R, and V53L) exhibited lower transactivation activities and variable DNA binding ability than wild-type PAX6 with PD DNA-binding consensus sequences. The mutated amino acids containing PAX6-5a isoforms showed unexpected transactivation properties with a reporter containing HD DNA-binding sequences. PAX6-5a-C52R, and -V53L showed lower transactivation activities, but PAX6-5a-L46R had greater transactivation ability than PAX6-5a. The PD-less isoform of Pax6 lost its transactivational ability but could bind to the HD DNA-binding sequences. Functional analysis of the PD-less isoform of Pax6 as well as findings related to missense mutations in the PD suggest that the PD of PAX6 is required for HD function.
Collapse
Affiliation(s)
- Rajnikant Mishra
- Department of Biochemistry and Molecular Biology, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
| | | | | | | | | |
Collapse
|