title: MeCP2 deficiency is associated with reduced levels of tubulin acetylation and can be restored using HDAC6 inhibitors.
abstract: Rett syndrome (RTT) is a severe neurodevelopmental disorder, predominantly caused by loss of function mutations in the X-linked methyl-CpG-binding protein 2 (MECP2) gene. Despite the genetic cause being known in the majority of cases, the pathophysiology of the neurological phenotype of RTT is largely unknown. Tubulin and the microtubule network play an essential role in neuronal function whereby the acetylation state of microtubules dictates the efficiency of neuronal migration and differentiation, synaptic targeting and molecular motor trafficking of mRNA, high-energy mitochondria and brain-derived neurotrophic factor (BDNF)-containing vesicles. Recent reports have shown perturbations in tubulin and microtubule dynamics in MeCP2-deficient cells, suggesting a link between the aberrations of these cellular entities and the neurobiology of RTT. We have interrogated the functional state of the microtubule network in fibroblasts derived from two patients with RTT as well as cortical neurons from a RTT mouse model and observed a reduction in acetylated α-tubulin and an increase in the tubulin-specific deacetylase, histone deacetylase 6 (HDAC6). Furthermore, we show that inhibition of HDAC6 by Tubastatin A can restore tubulin acetylation levels. We also demonstrate microtubule instability in the RTT patient fibroblasts in response to nocodazole, which is progressively ameliorated in a mutation-dependent manner by Tubastatin A. We conclude that Tubastatin A is capable of counteracting the microtubule defects observed in MeCP2-deficient cells, which could in turn lead to the restoration of molecular trafficking along the microtubules and thus could be a potentially new therapeutic option for RTT.
  
  
  CONCLUSIONS
  Cells from MeCP2-deficient cells show reduced levels of acetylated α-tubulin. Cells from two patients and a RTT mouse model have increased levels of HDAC6 but not sirtuin 2 (SIRT2). Inhibition of HDAC6 by Tubastatin A increases the in vitro acetylation of α-tubulin. Inhibition of HDAC6 by Tubastatin A does not increase MECP2 expression. Cells from two patients show microtubule instability, which is ameliorated by Tubastatin A.
authors.affiliation: NSW Centre for Rett Syndrome Research, Western Sydney Genetics Program, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, Sydney, New South Wales, 2145, Australia.
authors.forename: W A
authors.initials: WA
authors.lastname: Gold
authors.forename: T A
authors.initials: TA
authors.lastname: Lacina
authors.forename: L C
authors.initials: LC
authors.lastname: Cantrill
authors.forename: John
authors.initials: J
authors.lastname: Christodoulou
mesh_terms: D000107:Acetylation; D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D000073864:Histone Deacetylase 6; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006655:Histone Deacetylases / Q000378:metabolism*; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology*; D007211:Indoles / Q000494:pharmacology*; D008297:Male; D051783:Methyl-CpG-Binding Protein 2 / Q000235:genetics / Q000378:metabolism*; D008822:Mice, Transgenic; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D009154:Mutation; D012333:RNA, Messenger / Q000378:metabolism; D015518:Rett Syndrome / Q000235:genetics / Q000378:metabolism; D014404:Tubulin / Q000378:metabolism*
chemical_list: D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D007211:Indoles; D051783:Methyl-CpG-Binding Protein 2; D012333:RNA, Messenger; D014404:Tubulin; C553587:tubastatin A; C499033:Hdac6 protein, mouse; D000073864:Histone Deacetylase 6; D006655:Histone Deacetylases