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FB2026_01
,
released March 12, 2026
This report describes centronuclear myopathy, X-linked (CNMX), a sub-entity of centronuclear myopathy; it is inherited as a sex-linked recessive disorder. The human gene implicated in this disease is Myotubularin 1 (MTM1), which encodes a lipid and protein phosphatase that appears to be required for skeletal muscle maintenance, but not for myogenesis. There is a single fly ortholog, mtm, for which classical amorphic and missense alleles, RNAi-targeting constructs, and alleles caused by insertional mutagenesis have been generated. Dmel\mtm is also orthologous to two other genes in human, MTMR2 and MTMR1; the MTMR2 gene has been implicated in a form of Charcot-Marie-Tooth disease (MIM:603557).
The human MTM1 gene has not been introduced into flies.
Animals homozygous for an amorphic mutation of Dmel\mtm die during the larval stage. Use of muscle-specific GAL4 drivers to target RNAi-effected loss-of-function has allowed characterization of resulting muscle defects in adults. Physical and genetic interactions have been described for mtm; see below and in the gene report for mtm.
[updated Sep. 2016 by FlyBase; FBrf0222196]
Centronuclear myopathy is a congenital myopathy characterized by slowly progressive muscular weakness and wasting; the disorder involves mainly limb girdle, trunk, and neck muscles but may also affect distal muscles; ptosis (drooping eyelid) and limitation of eye movements may occur. Age of onset varies, from childhood to young adulthood. (Bitoun et al., 2005, pubmed:16227997). [from MIM:160150; 2015.12.16]
[MYOPATHY, CENTRONUCLEAR, X-LINKED; CNMX](https://omim.org/entry/310400)
[MYOTUBULARIN; MTM1](https://omim.org/entry/300415)
X-linked centronuclear myopathy is characterized by muscle weakness that ranges from severe to mild; it is not obviously progressive. In the severe form, newborns exhibit weakness, hypotonia, and respiratory distress; most fail to achieve independent ambulation and require 24-hour ventilatory assistance. [from Gene Reviews, X-Linked Centronuclear Myopathy; 2016.09.08]
X-linked centronuclear myopathy (CNMX) is caused by mutation in the myotubularin gene (MTM1).
CNMX is an X-linked recessive disorder; female carriers are generally asymptomatic. [from Gene Reviews, X-Linked Centronuclear Myopathy; 2016.09.08]
The characteristic muscle biopsy demonstrates numerous small, rounded myofibers with varying percentages of centrally located nuclei. [from Gene Reviews, X-Linked Centronuclear Myopathy; 2016.09.08]
The Myotubularin 1 (MTM1) gene encodes a lipid phosphatase; it also acts as dual-specificity protein phosphatase that acts on both phosphotyrosine and phosphoserine. It has multiple roles in endosomal transport, intermediate filament assembly and architecture, and mitochondrial morphology and positioning. It appears to be required for skeletal muscle maintenance, but not for myogenesis. [from Gene Cards, MTM1; 2016.09.09]
Many to one: 3 human to 1 Drosophila. The additional human genes are MTMR2 and MTMR1.