ATN1 encodes atrophin-1, a nuclear protein with transcriptional regulatory functions and one of the central genes in trinucleotide-repeat neurodegeneration. Pathogenic CAG repeat expansion in ATN1 causes Dentatorubral-Pallidoluysian Atrophy (DRPLA), an autosomal dominant polyglutamine disorder with progressive ataxia, myoclonus, epilepsy, cognitive impairment, and psychiatric symptoms [1][2].
The gene illustrates an important concept in neurogenetics: different classes of variants in the same locus can produce distinct clinical spectra. CAG expansion in exon 5 drives late-onset or juvenile neurodegeneration in DRPLA, whereas non-repeat de novo sequence variants in the HX motif are linked to ATN1-related neurodevelopmental disorder/CHEDDA syndrome. This allelic heterogeneity is increasingly relevant for counseling, variant interpretation, and therapeutic trial design [3][4].
| Attribute | Value |
|---|---|
| Gene Symbol | ATN1 |
| Full Name | Atrophin 1 |
| Chromosomal Location | 12p13.31 |
| NCBI Gene ID | 4722 |
| Ensembl ID | ENSG00000051617 |
| UniProt ID | O75576 |
| OMIM | 607462 |
| Protein Length | 1,187 amino acids |
| Molecular Weight | ~128 kDa |
| Expression | High in brain (cerebellum, basal ganglia), moderate in other tissues |
ATN1 encodes a nuclear protein that functions as a transcriptional co-repressor through multiple mechanisms. It is ubiquitously expressed with particularly high levels in the brain, where it plays critical roles in neuronal development, synaptic function, and cellular homeostasis [2:1][5].
ATN1 exerts its transcriptional regulatory functions through several mechanisms:
During development, ATN1 is essential for:
ATN1 participates in multiple homeostatic processes:
ATN1 protein contains several functional domains:
The polyQ expansion causes pathological protein aggregation and loss-of-function, leading to transcriptional dysregulation. Wild-type ATN1 has a relatively short polyQ tract, while mutant ATN1 contains an expanded tract that alters protein folding and aggregation propensity.
DRPLA is an autosomal dominant trinucleotide repeat disorder caused by CAG repeat expansion in the ATN1 gene. It represents one of the polyglutamine expansion diseases, sharing mechanisms with Huntington's disease, Machado-Joseph disease, and several spinocerebellar ataxias.
| Feature | Details |
|---|---|
| Normal repeat | 6-35 CAG repeats |
| Pathogenic repeat | 48-93 repeats |
| Anticipation | Earlier onset in subsequent generations (30-40 years in first generation, <20 years in later generations) |
| Prevalence | Rare: 0.5-1 per 100,000 (Japan), even rarer in Caucasian populations |
| Clinical features | Ataxia, choreoathetosis, dementia, myoclonus, epilepsy |
The polyQ expansion leads to:
Age at onset inversely correlates with CAG-repeat size, and juvenile-onset disease is often associated with epilepsy and severe progression, while adult-onset disease more commonly presents with ataxia/choreoathetosis and slower decline.
The polyQ expansion in ATN1 leads to widespread transcriptional changes:
Pathological ATN1 forms intranuclear aggregates:
Nucifora FC Jr, et al. Interference by expanded polyglutamine repeats. Brain Pathol (2002) — Mechanism studies
Wood JD, et al. Atrophin-1 is a transcriptional co-repressor. J Biol Chem (2002) — Transcriptional function
Shimohata T, et al. Expanded polyglutamine and apoptosis. Nat Neurosci (2000) — Cell death mechanisms
Suzuki K, et al. Molecular mechanisms in DRPLA. Int J Mol Sci (2020) — Comprehensive review
Takahashi H, et al. DRPLA: Clinical and molecular features. Brain Nerve (2012) — Clinical perspective
Karch CM, et al. Genetic modifiers in AD. Nat Rev Neurol (2015) — AD connection
Maloverjan A, et al. Therapies for polyglutamine diseases. Mol Ther (2018) — Therapeutic approaches
Orr CR, et al. Transcriptional co-repressors in neurodegeneration. Neurobiol Dis (2020) — Role in disease
Suzuki K, et al. ATN1 and polyglutamine diseases. Mol Neurobiol (2021) — Updated mechanisms
Chen X, et al. Polyglutamine expansion diseases. Nat Rev Neurol (2023) — Recent advances
Nucifora FC Jr, et al. "Interference by expanded polyglutamine repeats with the normal function of atrophin-1." Brain Pathology. Brain Pathology. 2002. ↩︎
Wood JD, et al. "Atrophin-1 (ATN1) is a transcriptional co-repressor involved in histone deacetylase-dependent repression." Journal of Biological Chemistry. Journal of Biological Chemistry. 2002. ↩︎ ↩︎
Takahashi H, et al. "Dentatorubral-pallidoluysian atrophy: Clinical features and molecular mechanisms." Brain and Nerve. Brain and Nerve. 2012. ↩︎
Karch CM, et al. "Genetic modifiers of Alzheimer's disease." Nature Reviews Neurology. Nature Reviews Neurology. 2015. ↩︎
Orr CR, et al. "The role of transcriptional co-repressors in neurodegenerative disease." Neurobiology of Disease. Neurobiology of Disease. 2020. ↩︎