title: A Multiplex Kindred with Hennekam Syndrome due to Homozygosity for a CCBE1 Mutation that does not Prevent Protein Expression.
abstract: Collagen and calcium-binding EGF domain-containing protein 1 (CCBE1) bi-allelic mutations have been associated with syndromes of widespread congenital lymphatic dysplasia, including Hennekam Syndrome (HS). HS is characterized by lymphedema, lymphangiectasia, and intellectual disability. CCBE1 encodes a putative extracellular matrix protein but the HS-causing mutations have not been studied biochemically. We report two HS siblings, born to consanguineous parents of Turkish ancestry, whose clinical phenotype also includes protein losing enteropathy, painful relapsing chylous ascites, and hypogammaglobulinemia. We identified by whole exome and Sanger sequencing the homozygous CCBE1 C174Y mutation in both siblings. This mutation had been previously reported in another HS kindred from the Netherlands. In over-expression studies, we found increased intracellular expression of all forms (monomers, dimers, trimers) of the CCBE1 C174Y mutant protein, by Western blot, despite mutant mRNA levels similar to wild-type (WT). In addition, we detected increased secretion of the mutant CCBE1 protein by ELISA. We further found the mutant and WT proteins to be evenly distributed in the cytoplasm, by immunofluorescence and confocal microscopy. Finally, we found a strong decrease of lymphatic vessels, with a corresponding diminished expression of CCBE1, by immunohistochemistry of the patients' intestinal biopsies. In contrast, mucosal blood vessels and muscularis mucosae showed normal CCBE1 staining. Our findings show that the mutant CCBE1 C174Y protein is not loss-of-function by loss-of-expression.
authors.affiliation: St. Giles Laboratory of Human Genetics of Infectious Diseases, Rockefeller Branch, The Rockefeller University, New York, NY, USA. cjackson@rockefeller.edu.|Department of Pediatrics, The Memorial Sloan Kettering Cancer Center, New York, NY, USA. cjackson@rockefeller.edu.
authors.forename: Carolyn C
authors.initials: CC
authors.lastname: Jackson
authors.affiliation: St. Giles Laboratory of Human Genetics of Infectious Diseases, Rockefeller Branch, The Rockefeller University, New York, NY, USA.
authors.forename: Lucy
authors.initials: L
authors.lastname: Best
authors.affiliation: Laboratory of Human Genetics of Infectious Diseases, Necker Branch, INSERM U1163, Necker Hospital for Sick Children, INSERM, Paris, France.
authors.forename: Lazaro
authors.initials: L
authors.lastname: Lorenzo
authors.affiliation: St. Giles Laboratory of Human Genetics of Infectious Diseases, Rockefeller Branch, The Rockefeller University, New York, NY, USA.|Laboratory of Human Genetics of Infectious Diseases, Necker Branch, INSERM U1163, Necker Hospital for Sick Children, INSERM, Paris, France.|Howard Hughes Medical Institute, New York, NY, USA.|Paris Descartes University, Imagine Institute, Paris, France.|Pediatric Hematology-Immunology Unit, Necker Hospital for Sick Children, Paris, France.
authors.forename: Jean-Laurent
authors.initials: JL
authors.lastname: Casanova
authors.affiliation: Department of Pathology, Universitätsklinikum Erlangen, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Wacker
authors.affiliation: Department of Pathology, Universitätsklinikum Erlangen, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Bertz
authors.affiliation: Department of Pathology, Universitätsklinikum Erlangen, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Abbas
authors.initials: A
authors.lastname: Agaimy
authors.affiliation: Department for Internal Medicine III, Universitätsklinikum Erlangen, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Harrer
mesh_terms: D000328:Adult; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D003241:Consanguinity; D019465:Craniofacial Abnormalities / Q000175:diagnosis* / Q000235:genetics; D004252:DNA Mutational Analysis; D005260:Female; D005786:Gene Expression Regulation / Q000235:genetics; D006720:Homozygote; D006801:Humans; D008201:Lymphangiectasis, Intestinal / Q000175:diagnosis* / Q000235:genetics; D008209:Lymphedema / Q000175:diagnosis* / Q000235:genetics; D008297:Male; D009154:Mutation / Q000235:genetics; D010375:Pedigree; D035781:Siblings; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D014421:Turkey; D055815:Young Adult
chemical_list: C546964:CCBE1 protein, human; D002135:Calcium-Binding Proteins; D025521:Tumor Suppressor Proteins
keywords: CCBE1; Hennekam Syndrome; lymphangiectasia; lymphedema