High frequency of copy number imbalances in Rubinstein-Taybi patients negative to CREBBP mutational analysis.
Rubinstein-Taybi syndrome (RSTS) is a rare autosomal dominant disorder characterised by facial dysmorphisms, growth and psychomotor development delay, and skeletal defects. The known genetic causes are point mutations or deletions of the CREBBP (50-60%) and EP300 (5%) genes. To detect chromosomal rearrangements indicating novel positional candidate RSTS genes, we used a-CGH to study 26 patients fulfilling the diagnostic criteria for RSTS who were negative at fluorescence in situ hybridisation analyses of the CREBBP and EP300 regions, and direct sequencing analyses of the CREBBP gene. We found seven imbalances (27%): four de novo and three inherited rearrangements not reported among the copy number variants. A de novo 7p21.1 deletion of 500 kb included the TWIST1 gene, a suggested candidate for RSTS that is responsible for the Saethre-Chotzen syndrome, an entity that enters in differential diagnosis with RSTS. A similar issue of differential diagnosis was raised by a large 4.3 Mb 2q22.3q23.1 deletion encompassing ZEB2, the gene responsible for the Mowat-Wilson syndrome, whose signs may overlap with RSTS. Positional candidate genes could not be sought in the remaining pathogenetic imbalances, because of the size of the involved region (a 9 Mb 2q24.3q31.1 deletion) and/or the relative paucity of suitable genes (a 5 Mb 3p13p12.3 duplication). One of the inherited rearrangements, the 17q11.2 379Kb duplication, represents the reciprocal event of the deletion underlying an overgrowth syndrome, both being mediated by the NF1-REP-P1 and REP-P2 sub-duplicons. The contribution of this and the other detected CNVs to the clinical RSTS phenotype is difficult to assess.
Gervasini
Cristina
C
Division of Medical Genetics, San Paolo School of Medicine, University of Milan, Milan, Italy.
Mottadelli
Federica
F
Ciccone
Roberto
R
Castronovo
Paola
P
Milani
Donatella
D
Scarano
Gioacchino
G
Bedeschi
Maria Francesca
MF
Belli
Serena
S
Pilotta
Alba
A
Selicorni
Angelo
A
Zuffardi
Orsetta
O
Larizza
Lidia
L
D000293:Adolescent; D000328:Adult; D022981:Allelic Imbalance / Q000235:genetics; D050882:CREB-Binding Protein / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D002874:Chromosome Mapping; D055028:Comparative Genomic Hybridization; D004252:DNA Mutational Analysis; D019066:Facies; D005260:Female; D005532:Foot Deformities, Congenital / Q000150:complications / Q000235:genetics; D018628:Gene Dosage / Q000235:genetics*; D015894:Genome, Human / Q000235:genetics; D006228:Hand Deformities, Congenital / Q000150:complications / Q000235:genetics; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D040582:Inheritance Patterns / Q000235:genetics; D008297:Male; D012415:Rubinstein-Taybi Syndrome / Q000150:complications / Q000235:genetics*; D055815:Young Adult
D050882:CREB-Binding Protein; C494363:CREBBP protein, human