Guidelines for genetic study of aniridia.

INTRODUCTION: Aniridia is a panocular disorder which occurs in 1/50,000 to 1/100,000 live births and can appear either in isolated form or in the context of a syndrome. Isolated aniridia is inherited as an autosomal dominant condition and is caused by mutations of the PAX6 gene. A variety of techniques and methodologies within molecular genetics and cytogenetics are used to study these mutations. OBJECTIVE: To identify the different aspects of this disease and to provide a guide for proper genetic diagnosis leading to improved clinical management of the disease. DEVELOPMENT: Aniridia is an autosomal dominant disease that primarily affects the iris, though it can impact most of the ocular structures. The disease is mainly caused by mutations in the PAX6 gene located on chromosome 11p13 which encodes a transcription factor that is involved in the development of the eye. Genetic analysis of aniridia is complex and requires the use of both molecular genetics and cytogenetics techniques. These procedures are indicated in all cases of aniridia. It is important bear certain clinical and technical aspects in mind prior to starting analysis or providing genetic counseling for patients and their families. CONCLUSIONS: The use of molecular genetic techniques in the genetic diagnosis of aniridia enables patients and their families to receive better clinical management.

Guía para el estudio genético de la aniridia / Guidelines for genetic study of aniridia

Introducción: La aniridia es una enfermedad panocular con una incidencia de entre 1/50.000 a 1/100.000 nacidos vivos, que puede presentarse de forma aislada o en el contexto de un síndrome. Presenta una herencia autosómica dominante y en la mayoría de los casos está causada por mutaciones en el gen PAX6, para cuyo estudio de mutaciones se emplea una gran variedad de técnicas y metodologías de genética molecular y citogenéticas. Objetivo: Recoger los distintos aspectos de esta enfermedad y ofrecer una guía para el adecuado diagnóstico genético que ayude a un mejor manejo clínico de la misma. Desarrollo: La aniridia es una enfermedad autosómica dominante que afecta fundamentalmente al iris, pero también puede afectar a la mayoría de las estructuras oculares. Está causada principalmente por mutaciones en el gen PAX6, ubicado en la región cromosómica 11p13, que codifica para una proteína reguladora de la transcripción imprescindible en el desarrollo del ojo. El análisis genético de la aniridia es complejo y requiere tanto de técnicas de genética molecular (secuenciación, CGH-array o MLPA) como citogenéticas (cariotipo y FISH). Este estudio está indicado en todos los casos de aniridia y es importante tener en cuenta ciertas consideraciones tanto clínicas como técnicas antes de abordar su análisis y el asesoramiento genético de los pacientes y familias afectados por esta enfermedad. Conclusiones: La aplicación de técnicas de genética molecular al diagnóstico genético de la aniridia permite un mejor manejo clínico tanto de los afectados como de sus familiares(AU)

Introduction: Aniridia is a panocular disorder which occurs in 1/50,000 to 1/100,000 live births and can appear either in isolated form or in the context of a syndrome. Isolated aniridia is inherited as an autosomal dominant condition and is caused by mutations of the PAX6 gene. A variety of techniques and methodologies within molecular genetics and cytogenetics are used to study these mutations. Objective: To identify the different aspects of this disease and to provide a guide for proper genetic diagnosis leading to improved clinical management of the disease. Development: Aniridia is an autosomal dominant disease that primarily affects the iris, though it can impact most of the ocular structures. The disease is mainly caused by mutations in the PAX6 gene located on chromosome 11p13 which encodes a transcription factor that is involved in the development of the eye. Genetic analysis of aniridia is complex and requires the use of both molecular genetics and cytogenetics techniques. These procedures are indicated in all cases of aniridia. It is important bear certain clinical and technical aspects in mind prior to starting analysis or providing genetic counseling for patients and their families. Conclusions: The use of molecular genetic techniques in the genetic diagnosis of aniridia enables patients and their families to receive better clinical management(AU)

Molecular analysis of the ABCA4 gene for reliable detection of allelic variations in Spanish patients: identification of 21 novel variants.

BACKGROUND/AIMS: Mutations in ABCA4 have been associated with autosomal recessive Stargardt disease (STGD), a few cases with autosomal recessive cone-rod dystrophy (arCRD) and autosomal recessive retinitis pigmentosa (arRP). The purpose of the study was threefold: to molecularly characterise families with no mutations or partially characterised families; to determine the specificity and sensitivity of the genotyping microarray; and to evaluate the efficiency of different methodologies. METHODS: 23 STGD, five arCRD and three arRP Spanish patients who were previously analysed with the ABCR400 microarray were re-evaluated. Results were confirmed by direct sequencing. In patients with either none or only one mutant allele, ABCA4 was further analysed by denaturing high-performance liquid chromatography (dHPLC) and multiplex ligation-dependent probe amplification (MLPA). Haplotype analysis was also performed. RESULTS: In the first analysis performed with the microarray, 27 ABCA4 variants (27/62; 43.5%) were found. By dHPLC scanning, 12 novel mutations were additionally identified. In addition, two previously described mutations, one false negative (1/62; 1.6%) and one false positive (1.6%), were detected. MLPA analysis did not reveal additional substitutions. The new strategy yielded an increment of 21% compared with the approach used in the first round. CONCLUSION: ABCA4 should be analysed by optimal combination of high-throughput screening techniques such as microarray, dHPLC and direct sequencing. To the best of our knowledge, this strategy yielded significant mutational spectrum identification in Spanish patients with ABCA4-associated phenotypes. Follow-up of patients, presenting an early onset of the disease and severe mutations, seems essential to perform accurate genotype-phenotype correlations and further characterisation of pathological ABCA4 alleles.