Microarray Analysis in Syndromic Obesity

Mental Retardation, Syndromic Obesity

CGH array technology, mental retardation, chromosomal abnormalities, syndromic obesity, obesity

Comparative genomic hybridization (CGH) array technology has been used in numerous studies on mental retardation, and few chromosomal abnormalities have been identified in patients. Because chromosomal abnormalities have still been associated with obesity, we can expect that syndromic obesity is also associated with small deletions/duplications. Characterization of deleted or duplicated loci in these obese patients would mean that these loci include genes implicated in obesity. This will permit to propose new gene(s) involved in obesity. (In french: Caractérisation phénotypique et recherche de REManiements chromosomiques chez des patients présentant une OBésité syndromique de cause non identifiée : REMOB)

With the introduction of array comparative genomic hybridization (CGH), genome-wide high resolution analysis for DNA copy number alterations became feasible. This technology has been principally used in patients with mental retardation. Depending on the eligibility criteria and resolution of the array, around 10 % of patients with mental retardation are found with cryptic chromosomal imbalance. This figure arises 20 % for patients with mental retardation and multiple congenital anomalies. Alteration of the lipid metabolism and/or regulation of satiety, obesity (except in presence of other "exogen" factors) can be considered as a developmental disorder. Also, different syndromes with obesity have been associated with chromosomal abnormalities, such as 1p36 deletion syndrome, 2q37 deletion syndrome, chromosome 14 maternal disomy … So we can expect that syndromic obesity is similarly associated with sub cryptic chromosomal abnormalities. Some "isolated" patients with obesity have been described with cryptic chromosomal imbalance found by array CGH, but no study has been realized in cohorts of patients selected for syndromic obesity. Characterization of cryptic chromosomal anomaly(ies) in a patient will also be useful to precise the management and follow-up of the patient and to give the family an adapted genetic counselling. We will define a cohort of patients with syndromic obesity and propose them to realize a first screening looking for the "common" aetiologies of syndromic obesity. If this screening is normal, array CGH will be realized. This analysis implies a blood sampling of 5 ml in patient and his parents. Genes present at the deleted or duplicated loci characterized in the patients will be study to determine if some could be specifically implicated in the development of obesity. These same genes could be implicated in isolated obesity. Our study will be also useful to precise the aetiological screening of syndromic obesity, and determine the place of array-CGH.

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