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FB2026_02
,
released June 18, 2026
This report describes spinocerebellar ataxia 36, which is a subtype of autosomal dominant spinocerebellar ataxia. The human gene implicated is NOP56, which encodes NOP56 ribonucleoprotein. There is one high-scoring fly ortholog, Dmel\Nop56, for which multiple genetic reagents, including classical alleles, RNAi-targeting constructs, and alleles caused by insertional mutagenesis have been generated.
Drosophila models of SCA36 make use of UAS constructs driving runs of hexanucleotide repeats of variable length; these are indicated as alleles of the synthetic gene Zzzz\GGGCCT. Multiple UAS constructs of the hexanucleotide repeat have been introduced into flies, including wild-type low copy number repeats, disease-associated expanded repeats, and constructs encoding dipeptide repeats in each reading frame (proline-glycine (PG), glycine-leucine (GL), and alanine-tryptophan (AW)).
The human gene NOP56 has not been introduced into flies.
Flies expressing Zzzz\GGGCCT constructs encoding 33 PG or AW dipeptide repeats exhibited formation of puncta characteristic of protein aggregation. Pan-neuronal expression of the dipeptide repeat constructs resulted in formation of stress granules, neurodegeneration, and impaired neuronal activities; these phenotypes were more pronounced in flies expressing PG or AW dipeptide repeats. Motor neuron-specific expression of dipeptide repeat constructs resulted in deformation of motor axons, and locomotor defects; these phenotypes were most pronounced in flies expressing PG dipeptide repeats. Motor neuron-specific expression of non-coding Zzzz\GGGCCT repeat expansions resulted in motor neuron defects and age-related locomotor defects; this phenotype was more pronounced in flies bearing 90 repeat constructs than those bearing 33 repeat constructs.
[updated Mar. 2026 by FlyBase; FBrf0222196]
The autosomal dominant cerebellar degenerative disorders are generally referred to as 'spinocerebellar ataxias,' (SCAs) even though 'spinocerebellar' is a hybrid term, referring to both clinical signs and neuroanatomical regions (Margolis, 2003, pubmed:14628900). Neuropathologists have defined SCAs as cerebellar ataxias with variable involvement of the brainstem and spinal cord, and the clinical features of the disorders are caused by degeneration of the cerebellum and its afferent and efferent connections, which involve the brainstem and spinal cord (Schols et al., 2004 pubmed:15099544; Taroni and DiDonato, 2004, pubmed:15263894). [From MIM:164400, 2015.10.27]
The autosomal dominant cerebellar degenerative disorders are generally referred to as 'spinocerebellar ataxias' (SCAs). Neuropathologists have defined SCAs as cerebellar ataxias with variable involvement of the brainstem and spinal cord; the clinical features of the disorders are caused by degeneration of the cerebellum and its afferent and efferent connections, which involve the brainstem and spinal cord (Schols et al., 2004 pubmed:15099544; Taroni and DiDonato, 2004, pubmed:15263894). [From MIM:164400, 2015.10.27]
[SPINOCEREBELLAR ATAXIA 36; SCA36](https://omim.org/entry/614153)
[NOP56 RIBONUCLEAR PROTEIN; NOP56](https://omim.org/entry/614154)
Spinocerebellar ataxia-36 (SCA36) is a slowly progressive neurodegenerative disorder characterized by adult-onset gait ataxia, eye movement abnormalities, tongue fasciculations, and variable upper motor neuron signs. Some affected individuals may develop hearing loss (summary by Garcia-Murias et al., 2012, pubmed:22492559). [from MIM:614153; 2026.03.06]
Spinocerebellar ataxia-36 (SCA36) is caused by heterozygous expansion of an intronic GGCCTG hexanucleotide repeat in the NOP56 gene on chromosome 20p13. Unaffected individuals carry 3 to 14 repeats, whereas affected individuals carry 650 to 2,500 repeats (Kobayashi et al., 2011, pubmed:21683323 and Garcia-Murias et al., 2012, pubmed:22492559). [from MIM:614153; 2026.03.06]
NOP56 is a component of the box C/D small nucleolar ribonucleoprotein complexes that direct 2-prime-O-methylation of pre-ribosomal RNA (rRNA) during its maturation. NOP56 is predicted to function in an early to middle step in pre-rRNA processing (Hayano et al., 2003, pubmed:12777385). [from MIM:614154; 2026.03.06]
One to one (1 human to 1 Drosophila); NOP56 has one high-scoring Drosophila ortholog, Nop56.
High-scoring ortholog of human NOP56 (1 Drosophila to 1 human).