RESUMEN
METHODS: The 22q13 deletion syndrome (MIM 606232) is characterised by moderate to profound mental retardation, delay/absence of expressive speech, hypotonia, normal to accelerated growth, and mild dysmorphic features. We have determined the deletion size and parent of origin in 56 patients with this syndrome. RESULTS: Similar to other terminal deletion syndromes, there was an overabundance of paternal deletions. The deletions vary widely in size, from 130 kb to over 9 Mb; however all 45 cases that could be specifically tested for the terminal region at the site of SHANK3 were deleted for this gene. The molecular structure of SHANK3 was further characterised. Comparison of clinical features to deletion size showed few correlations. Some measures of developmental assessment did correlate to deletion size; however, all patients showed some degree of mental retardation and severe delay or absence of expressive speech, regardless of deletion size. CONCLUSION: Our analysis therefore supports haploinsufficiency of the gene SHANK3, which codes for a structural protein of the postsynaptic density, as a major causative factor in the neurological symptoms of 22q13 deletion syndrome.
Asunto(s)
Proteínas Portadoras/genética , Deleción Cromosómica , Cromosomas Humanos Par 22/genética , Haplotipos/genética , Discapacidad Intelectual/genética , Trastornos del Desarrollo del Lenguaje/genética , Secuencia de Bases , Proteínas Portadoras/biosíntesis , Proteínas Portadoras/química , Mapeo Cromosómico/métodos , Análisis Citogenético , Discapacidades del Desarrollo/genética , Femenino , Humanos , Lactante , Masculino , Datos de Secuencia Molecular , Proteínas del Tejido Nervioso , Patentes como Asunto , Fenotipo , SíndromeRESUMEN
We have recently collected clinical information on 37 individuals with deletion of 22q13 and compared the features of these individuals with 24 previously reported cases. The features most frequently associated with this deletion are global developmental delay, generalized hypotonia, absent or severely delayed speech, and normal to advanced growth. Minor anomalies include dolicocephaly, abnormal ears, ptosis, dysplastic toenails, and relatively large hands. As with many terminal deletions involving pale G-band regions, the deletion can be extremely subtle and can go undetected on routine cytogenetic analysis. In fact, 32% of the individuals in our study had previous chromosome analyses that failed to detect the deletion. Eight of 37 individuals had deletion of 22q13 secondary to an unbalanced chromosome translocation. In the newborn, this deletion should be considered in cases of hypotonia for which other common causes have been excluded. In the older child, this syndrome should be suspected in individuals with normal growth, profound developmental delay, absent or delayed speech, and minor dysmorphic features. We recommend high-resolution chromosome analysis and fluorescence in situ hybridization studies, or molecular analysis to exclude this diagnosis.