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FB2026_01
,
released March 12, 2026
This report describes spastic paraplegia 92, an autosomal recessive subtype of spastic paraplegia. The human gene implicated is FICD, which encodes FIC domain protein adenylyltransferase, bifunctional enzyme that functions as an AMP transferase and as a phosphodiesterase. There is one high-scoring fly ortholog, Dmel\Fic, for which multiple genetic reagents, including amorphic alleles, RNAi-targeting constructs, and alleles caused by insertional mutagenesis have been generated.
Human FICD has not yet been introduced into flies.
Loss of function alleles of Dmel\Fic resulted in progressive impaired locomoter phenotypes, including decrease of walking speed, climbing ability, and an increase in slips, falls, and jumps, indicating a progressive deficiency of coordination and balance. These phenotypes were more marked in female flies.
[updated Dec. 2024 by FlyBase; FBrf0222196]
The hereditary spastic paraplegias (SPG, HSP) are a large group of clinically and genetically diverse disorders characterized by progressive, usually severe, lower extremity spasticity and weakness. SPG is classified by mode of inheritance (autosomal dominant, autosomal recessive, and X-linked) and whether the primary symptoms occur in isolation ('uncomplicated SPG') or with other neurologic abnormalities ('complicated SPG'). [from MIM:182600; 15.06.29]
[SPASTIC PARAPLEGIA 92, AUTOSOMAL RECESSIVE; SPG92](https://omim.org/entry/620911)
[FIC DOMAIN-CONTAINING PROTEIN ADENYLYLTRANSFERASE; FICD](https://omim.org/entry/620875)
Autosomal recessive spastic paraplegia-92 (SPG92) is a slowly progressive neurodegenerative disorder with onset of lower limb spasticity and gait abnormalities in the first (more common) or second decade of life. More variable features include upper limb involvement, tremor, urinary urgency, muscle weakness and atrophy, and mild peripheral neuropathy. Mild cognitive deficits have been reported in some patients (Rebelo et al., 2022, pubmed:36136088]). [from MIM:620911 2024.12.04]
Autosomal recessive spastic paraplegia-92 (SPG92) is caused by homozygous or compound heterozygous mutation in the FICD gene on chromosome 12q23. [from MIM:620911; 2024.12.04]
FICD is a bifunctional enzyme that functions as an AMP transferase that posttranslationally attaches an AMP moiety to target proteins (i.e., AMPylation or adenylylation) and as a phosphodiesterase that de-AMPylates the AMPylated proteins to release the AMP moiety (Sanyal et al., 2015, pubmed:25601083,; Preissler et al., 2017, pubmed:27918543; Perera et al., 2019, pubmed:31531998). [from MIM:620875; 2024.12.04]
One to one (1 human to 1 Drosophila); FICD has one high-scoring Drosophila ortholog, Fic.
High-scoring ortholog of human FICD, (1 Drosophila to 1 human).