An interstitial duplication of chromosome 13q31.3q32.1 further delineates the critical region for postaxial polydactyly type A2.
Postaxial polydactyly type A2 (PAP-A2; OMIM 602085) is a common feature seen in patients with a partial duplication of the long arm of chromosome 13. Dose dependency has been shown for digital malformations in this region, deletions resulting in oligodactyly and duplications in polydactyly. We aimed to narrow down the critical region for PAP-A2 in order to identify candidate genes. We performed chromosomal analysis, FISH and array-CGH in a patient with an interstitial duplication of chromosome 13q31.3q32.1 and a mild phenotype including postaxial polydactyly. The duplicated region spanned 5.59 Mb (89.67-95.25 Mb) and contained eleven known genes, including GPC5 and GPC6. GPC5 and GPC6 show homology with GPC3 and GPC4, genes involved in Simpson-Golabi-Behmel syndrome, an overgrowth syndrome in which also polydactyly can occur. Mouse studies have shown expression of both GPC5 and GPC6 in developing limbs. Therefore, we propose that GPC5 and GPC6 are the most likely candidate genes for PAP-A2.
van der Zwaag
Paul A
PA
Department of Genetics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
Dijkhuizen
Trijnie
T
Gerssen-Schoorl
Klasien B J
KB
Colijn
Anja W
AW
Broens
Paul M A
PM
Flapper
Boudien C T
BC
van Ravenswaaij-Arts
Conny M A
CM
D002675:Child, Preschool; D020223:Chromosome Painting; D002882:Chromosomes, Human, Pair 13; D055028:Comparative Genomic Hybridization; D005385:Fingers / Q000002:abnormalities*; D020440:Gene Duplication; D053673:Glypicans / Q000235:genetics; D006801:Humans; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D017689:Polydactyly / Q000235:genetics*
C120300:GPC6 protein, human; D053673:Glypicans