[New chromosomal syndromes].
Mental retardation occurs in 2-3% of the general population either in isolation or in combination with facial dysmorphism and/or malformations. Chromosomal abnormalities are a most common etiology. Karyotype displays chromosome aberrations in about 10% of patients but it has a limited resolution (5 Mb). Recently, the development of new molecular cytogenetic tools, especially array CGH, allowed to detect smaller abnormalities and increased the diagnosis capability of 15-20%. Among these newly detected rearrangements, some of them are recurrent and define new recognized syndromes. We will first briefly explain the non-allelic homologous recombination (NAHR) mechanism that underlines the origin of recurrent microdeletions and microduplications. Then we will describe eight new syndromes, four microdeletions (del 17q21.31, del 3q29, del 15q24, del 2q32.3q33) and four microduplications (dup 22q11.2, dup 7q11.23, dup 17p11.2, duplication of MECP2). A better knowledge of these new recurrent chromosomal syndromes will allow to improve care for patients, to develop targeted chromosomal diagnosis and to identify genes involved in neurocognitive functions.
Schluth-Bolard
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Service de cytogénétique constitutionnelle, hospices civils de Lyon, centre de biologie et de pathologie Est, 59, boulevard Pinel, 69677 Bron, cedex, France.
Till
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Edery
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Sanlaville
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D
D000015:Abnormalities, Multiple / Q000235:genetics; D002872:Chromosome Deletion; D025063:Chromosome Disorders / Q000145:classification* / Q000235:genetics; D002880:Chromosomes, Human, Pair 11 / Q000235:genetics / Q000648:ultrastructure; D002884:Chromosomes, Human, Pair 15 / Q000235:genetics / Q000648:ultrastructure; D002886:Chromosomes, Human, Pair 17 / Q000235:genetics / Q000648:ultrastructure; D002889:Chromosomes, Human, Pair 2 / Q000235:genetics / Q000648:ultrastructure; D002893:Chromosomes, Human, Pair 3 / Q000235:genetics / Q000648:ultrastructure; D002897:Chromosomes, Human, Pair 7 / Q000235:genetics / Q000648:ultrastructure; D020440:Gene Duplication; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics; D007621:Karyotyping; D051783:Methyl-CpG-Binding Protein 2 / Q000235:genetics; D009693:Nucleic Acid Hybridization; D011995:Recombination, Genetic; D017384:Sequence Deletion; D013577:Syndrome
C497392:MECP2 protein, human; D051783:Methyl-CpG-Binding Protein 2