A point mutation in the pre-ZRS disrupts sonic hedgehog expression in the limb bud and results in triphalangeal thumb-polysyndactyly syndrome.
PURPOSE
The zone of polarizing activity regulatory sequence (ZRS) is an enhancer that regulates sonic hedgehog during embryonic limb development. Recently, mutations in a noncoding evolutionary conserved sequence 500 bp upstream of the ZRS, termed the pre-ZRS (pZRS), have been associated with polydactyly in dogs and humans. Here, we report the first case of triphalangeal thumb-polysyndactyly syndrome (TPT-PS) to be associated with mutations in this region and show via mouse enhancer assays how this mutation leads to ectopic expression throughout the developing limb bud.


METHODS
We used linkage analysis, whole-exome sequencing, Sanger sequencing, fluorescence in situ hybridization, multiplex ligation-dependent probe amplification, single-nucleotide polymorphism array, and a mouse transgenic enhancer assay.


RESULTS
Ten members of a TPT-PS family were included in this study. The mutation was linked to chromosome 7q36 (LOD score 3.0). No aberrations in the ZRS could be identified. A point mutation in the pZRS (chr7:156585476G>C; GRCh37/hg19) was detected in all affected family members. Functional characterization using a mouse transgenic enhancer essay showed extended ectopic expression dispersed throughout the entire limb bud (E11.5).


CONCLUSION
Our work describes the first mutation in the pZRS to be associated with TPT-PS and provides functional evidence that this mutation leads to ectopic expression of this enhancer within the developing limb.
['Potuijt|Jacob W P|JWP|', 'Baas|Martijn|M|', 'Sukenik-Halevy|Rivka|R|', 'Douben|Hannie|H|', 'Nguyen|Picard|P|', 'Venter|Deon J|DJ|', 'Gallagher|Renée|R|', 'Swagemakers|Sigrid M|SM|', 'Hovius|Steven E R|SER|', 'van Nieuwenhoven|Christianne A|CA|', 'Galjaard|Robert-Jan H|RH|', 'van der Spek|Peter J|PJ|', 'Ahituv|Nadav|N|', 'de Klein|Annelies|A|']
D000818:Animals D002897:Chromosomes, Human, Pair 7 D000013:Congenital Abnormalities D004742:Enhancer Elements, Genetic D005260:Female D005786:Gene Expression Regulation D008040:Genetic Linkage D020022:Genetic Predisposition to Disease D053823:Hedgehog Proteins D006801:Humans D017404:In Situ Hybridization, Fluorescence D018878:Limb Buds D008297:Male D008342:Mandibulofacial Dysostosis D008565:Membrane Proteins D051379:Mice D010375:Pedigree D017354:Point Mutation D020641:Polymorphism, Single Nucleotide D000073359:Whole Exome Sequencing
polydactyly congenital limb deformities genetic enhancer elements hedgehog protein syndactyly