title: Loss-of-function of MYO5B is the main cause of microvillus inclusion disease: 15 novel mutations and a CaCo-2 RNAi cell model.
abstract: Autosomal recessive microvillus inclusion disease (MVID) is characterized by an intractable diarrhea starting within the first few weeks of life. The hallmarks of MVID are a lack of microvilli on the surface of villous enterocytes, occurrence of intracellular vacuoles lined by microvilli (microvillus inclusions), and the cytoplasmic accumulation of periodic acid-Schiff (PAS)-positive vesicles in enterocytes. Recently, we identified mutations in MYO5B, encoding the unconventional type Vb myosin motor protein, in a first cohort of nine MVID patients. In this study, we identified 15 novel nonsense and missense mutations in MYO5B in 11 unrelated MVID patients. Fluorescence microscopy, Western blotting, and electron microscopy were applied to analyze the effects of MYO5B siRNA knock-down in polarized, brush border possessing CaCo-2 cells. Loss of surface microvilli, increased formation of microvillus inclusions, and subapical enrichment of PAS-positive endomembrane compartments were induced in polarized, filter-grown CaCo-2 cells, following MYO5B knock-down. Our data indicate that MYO5B mutations are a major cause of microvillus inclusion disease and that MYO5B knock-down recapitulates most of the cellular phenotype in vitro, thus independently showing loss of MYO5B function as the cause of microvillus inclusion disease.
authors.affiliation: Université Paris Descartes, Faculté Necker, INSERM U793, Paris, France.
authors.forename: Frank M
authors.initials: FM
authors.lastname: Ruemmele
authors.forename: Thomas
authors.initials: T
authors.lastname: Müller
authors.forename: Natalia
authors.initials: N
authors.lastname: Schiefermeier
authors.forename: Hannes L
authors.initials: HL
authors.lastname: Ebner
authors.forename: Silvia
authors.initials: S
authors.lastname: Lechner
authors.forename: Kristian
authors.initials: K
authors.lastname: Pfaller
authors.forename: Cornelia E
authors.initials: CE
authors.lastname: Thöni
authors.forename: Olivier
authors.initials: O
authors.lastname: Goulet
authors.forename: Florence
authors.initials: F
authors.lastname: Lacaille
authors.forename: Jacques
authors.initials: J
authors.lastname: Schmitz
authors.forename: Virginie
authors.initials: V
authors.lastname: Colomb
authors.forename: Frédérique
authors.initials: F
authors.lastname: Sauvat
authors.forename: Yann
authors.initials: Y
authors.lastname: Revillon
authors.forename: Danielle
authors.initials: D
authors.lastname: Canioni
authors.forename: Nicole
authors.initials: N
authors.lastname: Brousse
authors.forename: Genevieve
authors.initials: G
authors.lastname: de Saint-Basile
authors.forename: Juliette
authors.initials: J
authors.lastname: Lefebvre
authors.forename: Peter
authors.initials: P
authors.lastname: Heinz-Erian
authors.forename: Axel
authors.initials: A
authors.lastname: Enninger
authors.forename: Gerd
authors.initials: G
authors.lastname: Utermann
authors.forename: Michael W
authors.initials: MW
authors.lastname: Hess
authors.forename: Andreas R
authors.initials: AR
authors.lastname: Janecke
authors.forename: Lukas A
authors.initials: LA
authors.lastname: Huber
mesh_terms: D000293:Adolescent; D015153:Blotting, Western; D018938:Caco-2 Cells; D002648:Child; D002675:Child, Preschool; D018389:Codon, Nonsense / Q000235:genetics; D004252:DNA Mutational Analysis; D003968:Diarrhea, Infantile / Q000235:genetics*; D004065:Digestive System Abnormalities / Q000235:genetics*; D005260:Female; D006801:Humans; D007223:Infant; D008286:Malabsorption Syndromes / Q000235:genetics*; D008297:Male; D008871:Microvilli / Q000473:pathology*; D020125:Mutation, Missense / Q000235:genetics; D018995:Myosin Heavy Chains / Q000235:genetics* / Q000378:metabolism; D024701:Myosin Type V / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference / Q000502:physiology
chemical_list: D018389:Codon, Nonsense; C505832:MYO5B protein, human; D024701:Myosin Type V; D018995:Myosin Heavy Chains