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  • Articles  (2)
  • BioMed Central  (1)
  • Nature Publishing Group (NPG)
  • 2010-2014  (2)
  • 2012  (2)
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  • 1
    Publication Date: 2012-05-25
    Description: An outstanding question is how cells control the number and size of membrane organelles. The small GTPase Rab5 has been proposed to be a master regulator of endosome biogenesis. Here, to test this hypothesis, we developed a mathematical model of endosome dependency on Rab5 and validated it by titrating down all three Rab5 isoforms in adult mouse liver using state-of-the-art RNA interference technology. Unexpectedly, the endocytic system was resilient to depletion of Rab5 and collapsed only when Rab5 decreased to a critical level. Loss of Rab5 below this threshold caused a marked reduction in the number of early endosomes, late endosomes and lysosomes, associated with a block of low-density lipoprotein endocytosis. Loss of endosomes caused failure to deliver apical proteins to the bile canaliculi, suggesting a requirement for polarized cargo sorting. Our results demonstrate for the first time, to our knowledge, the role of Rab5 as an endosome organizer in vivo and reveal the resilience mechanisms of the endocytic system.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zeigerer, Anja -- Gilleron, Jerome -- Bogorad, Roman L -- Marsico, Giovanni -- Nonaka, Hidenori -- Seifert, Sarah -- Epstein-Barash, Hila -- Kuchimanchi, Satya -- Peng, Chang Geng -- Ruda, Vera M -- Del Conte-Zerial, Perla -- Hengstler, Jan G -- Kalaidzidis, Yannis -- Koteliansky, Victor -- Zerial, Marino -- England -- Nature. 2012 May 23;485(7399):465-70. doi: 10.1038/nature11133.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22622570" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Polarity ; Cells, Cultured ; Endocytosis ; Endosomes/*metabolism ; Gene Knockdown Techniques ; Hepatocytes/cytology/metabolism ; Isoenzymes/biosynthesis/deficiency/genetics/metabolism ; Lipoproteins, LDL/metabolism ; Liver/cytology/enzymology/metabolism ; Lysosomes/*metabolism ; Mice ; Multivesicular Bodies/metabolism ; Organ Specificity ; Protein Biosynthesis ; RNA Interference ; RNA, Messenger/analysis/genetics ; Time Factors ; Vesicular Transport Proteins/metabolism ; rab5 GTP-Binding Proteins/biosynthesis/deficiency/genetics/*metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2012-03-22
    Description: Background Pierre-Robin sequence (PRS) is defined by micro- and/or retrognathia, glossoptosis and cleft soft palate, either caused by deformational defect or part of a malformation syndrome. Neurofibromatosis type 2 (NF2) is an autosomal dominant syndrome caused by mutations in the NF2 gene on chromosome 22q12.2. NF2 is characterized by bilateral vestibular schwannomas, spinal cord schwannomas, meningiomas and ependymomas, and juvenile cataracts. To date, NF2 and PRS have not been described together in the same patient. Case presentation We report a female with PRS (micrognathia, cleft palate), microcephaly, ocular hypertelorism, mental retardation and bilateral hearing loss, who at age 15 was also diagnosed with severe NF2 (bilateral cerebellopontine schwannomas and multiple extramedullary/intradural spine tumors). This is the first published report of an individual with both diagnosed PRS and NF2. High resolution karyotype revealed 46, XX, del(22)(q12.1q12.3), FISH confirmed a deletion encompassing NF2, and chromosomal microarray identified a 3,693 kb deletion encompassing multiple genes including NF2 and MN1 (meningioma 1). Five additional patients with craniofacial dysmorphism and deletion in chromosome 22-adjacent-to or containing NF2 were identified in PubMed and the DECIPHER clinical chromosomal database. Their shared chromosomal deletion encompassed MN1, PITPNB and TTC28. MN1, initially cloned from a patient with meningioma, is an oncogene in murine hematopoiesis and participates as a fusion gene (TEL/MN1) in human myeloid leukemias. Interestingly, Mn1-haploinsufficient mice have abnormal skull development and secondary cleft palate. Additionally, Mn1 regulates maturation and function of calvarial osteoblasts and is an upstream regulator of Tbx22, a gene associated with murine and human cleft palate. This suggests that deletion of MN1 in the six patients we describe may be causally linked to their cleft palates and/or craniofacial abnormalities. Conclusions Thus, our report describes a NF2-adjacent chromosome 22q12.2 deletion syndrome and is the first to report association of MN1 deletion with abnormal craniofacial development and/or cleft palate in humans.
    Electronic ISSN: 1471-2350
    Topics: Biology , Medicine
    Published by BioMed Central
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