Fine mapping of whole RB1 gene deletions in retinoblastoma patients confirms PCDH8 as a candidate gene for psychomotor delay.
Retinoblastoma (Rb) results from inactivation of both alleles of the RB1 gene located in 13q14.2. Whole-germline monoallelic deletions of the RB1 gene (6% of RB1 mutational spectrum) sometimes cause a variable degree of psychomotor delay and several dysmorphic abnormalities. Breakpoints in 12 Rb patients with or without psychomotor delay were mapped to specifically define the role of chromosomal regions adjacent to RB1 in psychomotor delay. A high-resolution CGH array focusing on RB1 and its flanking region was designed to precisely map the deletion. Comparative analysis detected a 4-Mb critical interval, including a candidate gene protocadherin 8 (PCDH8). PCDH8 is thought to function in signalling pathways and cell adhesion in a central nervous system-specific manner, making loss of PCDH8 one of the probable causes of psychomotor delay in RB1-deleted patients. Consequently, we propose to systematically use high-resolution CGH in cases of partial or complete RB1 deletion encompassing the telomeric flanking region to characterize the putative loss of PCDH8 and to better define genotype/phenotype correlations, eventually leading to optimized genetic counselling and psychomotor follow-up.
Département de Biologie des Tumeurs, Institut Curie, Paris, France.
Laurent
L
Castéra
Catherine
C
Dehainault
Dorothée
D
Michaux
Livia
L
Lumbroso-Le Rouic
Isabelle
I
Aerts
Francois
F
Doz
Anna
A
Pelet
Jérôme
J
Couturier
Dominique
D
Stoppa-Lyonnet
Marion
M
Gauthier-Villars
Claude
C
Houdayer
D000328:Adult; D015820:Cadherins / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D056905:Chromosome Breakpoints; D002874:Chromosome Mapping; D055028:Comparative Genomic Hybridization; D002658:Developmental Disabilities / Q000175:diagnosis / Q000235:genetics; D005260:Female; D017353:Gene Deletion; D016161:Genes, Retinoblastoma; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D000091363:Protocadherins; D011596:Psychomotor Disorders / Q000175:diagnosis / Q000235:genetics*; D019572:Retinal Neoplasms / Q000175:diagnosis / Q000235:genetics*; D012175:Retinoblastoma / Q000175:diagnosis / Q000235:genetics*
D015820:Cadherins; C115816:PCDH8 protein, human; D000091363:Protocadherins