Encyclopedia
MN1 C-terminal truncation (MCTT) syndrome is a condition characterized by intellectual disability, developmental delay, distinctive facial features, and brain abnormalities.
- genetic conditions
Frequency
The prevalence of MCTT syndrome is unknown, although it is thought to be a rare disorder. At least 25 affected individuals have been described in the scientific literature.
Causes
MCTT syndrome is caused by mutations in the MN1 gene. This gene provides instructions for making a protein whose function is unclear. Based on its interaction with other proteins, the MN1 protein is thought to play a role in regulating the activity of other genes, particularly those needed for the development of the skull and brain.
All MN1 gene mutations that cause MCTT syndrome occur near the end (terminal) portion of the gene. As a result, an abnormally short (truncated) protein is produced. These mutations are reflected in the condition name, MN1 C-terminal truncation syndrome.
Research shows that a shortened MN1 protein cannot interact with other proteins, leading to a buildup of the abnormal MN1 protein in the cell nucleus. It is likely that without the normal function of the MN1 protein, the activity of certain genes involved in the development of the skull and brain is unregulated, leading to the signs and symptoms of MCTT syndrome.
Inheritance
MCTT syndrome is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.
Most cases of this condition result from new (de novo) mutations in the MN1 gene that occur during the formation of reproductive cells (eggs or sperm) in an affected individual's parent or in early embryonic development. These cases occur in people with no history of the disorder in their family.
Other Names for This Condition
- CEBALID
- craniofacial defects, dysmorphic ears, structural brain abnormalities, expressive language delay, and impaired intellectual development
- MCTT syndrome
This entry is adapted from the peer-reviewed paper https://medlineplus.gov/genetics/condition/mn1-c-terminal-truncation-syndrome
References
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- Mak CCY, Fung JLF, Lee M, Lin AE, Amiel J, Doherty D, Gordon CT, Chung BHY.MN1 C-Terminal Truncation Syndrome. 2020 Aug 13. In: Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Stephens K, Amemiya A, editors. GeneReviews®[Internet]. Seattle (WA): University of Washington, Seattle; 1993-2020. Availablefrom http://www.ncbi.nlm.nih.gov/books/NBK560443/
- Miyake N, Takahashi H, Nakamura K, Isidor B, Hiraki Y, Koshimizu E, Shiina M, Sasaki K, Suzuki H, Abe R, Kimura Y, Akiyama T, Tomizawa SI, Hirose T, HamanakaK, Miyatake S, Mitsuhashi S, Mizuguchi T, Takata A, Obo K, Kato M, Ogata K,Matsumoto N. Gain-of-Function MN1 Truncation Variants Cause a RecognizableSyndrome with Craniofacial and Brain Abnormalities. Am J Hum Genet. 2020 Jan2;106(1):13-25. doi: 10.1016/j.ajhg.2019.11.011.
