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[Genetic study of holoprosencephaly]
C Dubourg1, L Lazaro, M Blayau
1Laboratoire de génétique moléculaire, CHU Pontchaillou, 35033 Rennes. christele.dubourg@chu-rennes.fr
Annales De Biologie Clinique
|January 9, 2004
Summary
Holoprosencephaly is a brain malformation with variable symptoms, often caused by genetic mutations. This study identified mutations in SHH, ZIC2, SIX3, and TGIF genes, highlighting genetic heterogeneity and diverse phenotypes.
Area of Science:
- Neuroscience
- Developmental Biology
- Genetics
Context:
- Holoprosencephaly (HPE) is a spectrum of congenital brain malformations due to incomplete forebrain cleavage.
- Incidence varies, affecting 1/16,000 live births and 1/250 conceptuses.
- HPE exhibits significant genetic heterogeneity and variable expressivity, influenced by genetic and environmental factors.
Purpose:
- To investigate the genetic basis of holoprosencephaly in a cohort of 143 patients.
- To identify specific gene mutations contributing to HPE.
- To correlate identified mutations with clinical phenotypes and assess genotype-phenotype relationships.
Summary:
- Identified 28 heterozygous mutations in 143 patients: 15 in Sonic hedgehog (SHH), 6 in ZIC2, 5 in SIX3, and 2 in TGIF.
- Functional tests were employed to validate the significance of SHH amino acid substitutions.
- Described novel phenotypes, including pituitary and corpus callosum abnormalities, colobomatous microphthalmia, choanal atresia, and isolated cleft lip.
Impact:
- Confirms significant genetic heterogeneity in holoprosencephaly.
- Highlights substantial phenotypic variability within holoprosencephalic families.
- Suggests an absence of clear genotype-phenotype correlations, complicating diagnosis and prediction.