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Duplications of BHLHA9 are associated with ectrodactyly and tibia hemimelia inherited in non-Mendelian fashion
  1. Eva Klopocki1,2,
  2. Silke Lohan1,2,
  3. Sandra C Doelken1,
  4. Sigmar Stricker2,
  5. Charlotte W Ockeloen3,
  6. Renata Soares Thiele de Aguiar4,
  7. Karina Lezirovitz4,5,
  8. Regina Celia Mingroni Netto4,
  9. Aleksander Jamsheer6,7,
  10. Hitesh Shah8,
  11. Ingo Kurth9,
  12. Rolf Habenicht10,
  13. Matthew Warman11,
  14. Koenraad Devriendt12,
  15. Ulrike Kordaß13,
  16. Maja Hempel14,15,
  17. Anna Rajab16,
  18. Outi Mäkitie17,
  19. Mohammed Naveed18,
  20. Uppala Radhakrishna19,
  21. Stylianos E Antonarakis19,20,
  22. Denise Horn1,
  23. Stefan Mundlos1,2
  1. 1Institute for Medical Genetics and Human Genetics, Charité—Universitätsmedizin Berlin, Berlin, Germany
  2. 2Max-Planck-Institute for Molecular Genetics, Berlin, Germany
  3. 3Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
  4. 4Centro de Estudos do Genoma Humano, Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
  5. 5Laboratório de Otorrinolaringologia/LIM32, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
  6. 6Department of Medical Genetics, University of Medical Sciences, Poznan, Poland
  7. 7NZOZ Center for Medical Genetics GENESIS, Poznan, Poland
  8. 8Department of Orthopaedics, Paediatric Orthopaedic Service, Kasturba Medical College, Manipal, Karnataka, India
  9. 9Institut für Humangenetik, Universitätsklinikum Jena, Jena, Germany
  10. 10Kath. Kinderkrankenhaus Wilhemstift, Hamburg, Germany
  11. 11Orthopaedic Research Laboratories, Department of Orthopaedic Surgery, The Howard Hughes Medical Institute, Children's Hospital, Boston, Massachusetts, USA
  12. 12Department of Medical Genetics, Leuven University Hospital, Leuven, Belgium
  13. 13Institute for Human Genetics, Universitätsmedizin Greifswald, Greifswald, Germany
  14. 14Institute of Human Genetics, Technische Universität München, Munich, Germany
  15. 15Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany
  16. 16Department of Genetics, Directorate General of Health Affairs, Ministry of Health, Muscat, Sultanate of Oman
  17. 17Children's Hospital, Helsinki University Central Hospital, University of Helsinki, and Folkhälsan Institute of Genetics, Helsinki, Finland
  18. 18Center for Arab Genomic Studies (CAGS), Dubai, United Arab Emirates
  19. 19Department of Genetic Medicine and Development, University of Geneva Medical School, Geneva, Switzerland
  20. 20Division of Medical Genetics, Geneva University Hospitals, Geneva, Switzerland
  1. Correspondence to Dr Eva Klopocki, Institute for Medical Genetics and Human Genetics, Charité Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany; eva.klopocki{at}charite.de

Abstract

Background Split-hand/foot malformation (SHFM)—also known as ectrodactyly—is a congenital disorder characterised by severe malformations of the distal limbs affecting the central rays of hands and/or feet. A distinct entity termed SHFLD presents with SHFM and long bone deficiency. Mouse models suggest that a defect of the central apical ectodermal ridge leads to the phenotype. Although six different loci/mutations (SHFM1–6) have been associated with SHFM, the underlying cause in a large number of cases is still unresolved.

Methods High resolution array comparative genomic hybridisation (CGH) was performed in patients with SHFLD to detect copy number changes. Candidate genes were further evaluated for expression and function during limb development by whole mount in situ hybridisation and morpholino knock-down experiments.

Results Array CGH showed microduplications on chromosome 17p13.3, a locus previously associated with SHFLD. Detailed analysis of 17 families revealed that this copy number variation serves as a susceptibility factor for a highly variable phenotype with reduced penetrance, particularly in females. Compared to other known causes for SHFLD 17p duplications appear to be the most frequent cause of SHFLD. A ∼11.8 kb minimal critical region was identified encompassing a single gene, BHLHA9, a putative basic loop helix transcription factor. Whole mount in situ hybridisation showed expression restricted to the limb bud mesenchyme underlying the apical ectodermal ridge in mouse and zebrafish embryos. Knock down of bhlha9 in zebrafish resulted in shortening of the pectoral fins.

Conclusions Genomic duplications encompassing BHLHA9 are associated with SHFLD and non-Mendelian inheritance characterised by a high degree of non-penetrance with sex bias. Knock-down of bhlha9 in zebrafish causes severe reduction defects of the pectoral fin, indicating a role for this gene in limb development.

  • Copy-number variation
  • split-hand/foot malformation (SHFM)
  • SHFLD
  • congenital limb malformation
  • chromosomal
  • clinical genetics
  • copy-number
  • genetics
  • microarray
  • aneuploidy
  • developmental
  • cell biology
  • genetic screening/counselling
  • linkage
  • molecular genetics
  • hearing loss
  • osteoporosis
  • osteoarthritis
  • neurology
  • peripheral nerve disease
  • calcium and bone
  • endocrinology
  • diagnostics
  • gene therapy
  • genome-wide
  • academic medicine
  • complex traits

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Footnotes

  • Funding This work was supported by the Deutsche Forschungsgemeinschaft to EK and SM (grant number KL 2158/2-1). AJ was supported by a grant from the Polish Ministry of Science and Higher Education (grant number 495/N-NIEMCY/2009/0).

  • Competing interests None.

  • Patient consent Obtained.

  • Ethics approval Ethics committee of Charité Universitätsmedizin Berlin.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement Primer sequences not given in the text are available upon request.

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