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FB2026_01
,
released March 12, 2026
This report describes Waisman syndrome, an X-linked neurological disorder characterized by developmental delay and early-onset Parkinson disease. The human gene implicated is RAB39B, a small GTPase involved in the regulation of vesicular trafficking. RAB39B is also associated with X-linked intellectual developmental disorder 72 (MIM:300271), which is not associated with parkinsonism. There is one high-scoring fly ortholog, Dmel\Rab39, for which multiple genetic reagents, including classical and amorphic alleles, RNAi-targeting constructs, and alleles caused by insertional mutagenesis have been generated.
Wild-type human Hsap\RAB39B have been introduced into flies. Additionally, variants implicated in human disease were introduced as knock-in alleles; see the 'Disease-Implicated Variants' table below.
Single-cell RNAseq analysis of the knock-in mutant Hsap\RAB39B alleles indicate that olfactory projection neurons are impaired. Adults carrying this mutation demonstate hyposmia.
[updated June 2025 by FlyBase; FBrf0222196]
Parkinson disease (PD) is a neurodegenerative disease usually typified by slow onset in mid to late adulthood; there are also early-onset and juvenile forms of the disease. Symptoms worsen over time and include resting tremor, muscular rigidity, bradykinesia [abnormal slowness of movement], and postural instability [impaired balance and coordination]; additional symptoms may include postural abnormalities, dysautonomia [symptoms caused by malfunction of the autonomic nervous system], dystonic cramps, and dementia. Parkinson disease is the second-most common neurodegenerative disease (after Alzheimer disease), affecting approximately 1% of the population over 50 (Polymeropoulos et al., 1996, pubmed:8895469). [from MIM:168600; 2013.07.23]
Parkinson disease is described as early-onset disease if signs and symptoms begin before age 50. Early-onset cases that begin before age 20 may be referred to as juvenile-onset disease. [from Genetics Home Reference, GHR_condition:parkinson-disease, 2015.02.13]
[WAISMAN SYNDROME; WSMN](https://omim.org/entry/311510)
[RAB39B, MEMBER RAS ONCOGENE FAMILY; RAB39B](https://omim.org/entry/300774)
Waisman syndrome (WSMN) is an X-linked neurologic disorder characterized by delayed psychomotor development, impaired intellectual development, and early-onset Parkinson disease (summary by Wilson et al., 2014; pubmed:25434005). The transmission pattern of Waisman syndrome in the families reported by Laxova et al. (1985, pubmed:4025396) and Wilson et al. (2014, pubmed:25434005) was consistent with X-linked recessive inheritance. [from MIM:311510; 2025.06.03]
Waisman syndrome (WSMN) is caused by mutation in the RAB39B gene on chromosome Xq28. [from MIM:311510; 2025.06.03]
Mutation in the RAB39B gene has also been found in patients with X-linked intellectual developmental disorder 72 (XLID72; MIM:300271); Parkinson disease has not been reported in patients with XLID72. [from MIM:311510; 2025.06.03]
RAB proteins, such as RAB39B, are small GTPases involved in the regulation of vesicular trafficking between membrane compartments (Cheng et al., 2002; pubmed:12438742). [from MIM:300774; 2025.06.03]
One to two (1 human to 2 Drosophila); RAB39B has one high-scoring Drosophila ortholog, Rab39.
High-scoring ortholog of human RAB39A and RAB39B (2 Drosophila to 1 human).