Sensory neuropathy with bone destruction due to a mutation in the membrane-shaping atlastin GTPase 3

Abstract

Many neurodegenerative disorders present with sensory loss. In the group of hereditary sensory and autonomic neuropathies loss of nociception is one of the disease hallmarks. To determine underlying factors of sensory neurodegeneration we performed whole-exome sequencing in affected individuals with the disorder. In a family with sensory neuropathy with loss of pain perception and destruction of the pedal skeleton we report a missense mutation in a highly conserved amino acid residue of atlastin GTPase 3 (ATL3), an endoplasmic reticulum-shaping GTPase. The same mutation (p.Tyr192Cys) was identified in a second family with similar clinical outcome by screening a large cohort of 115 patients with hereditary sensory and autonomic neuropathies. Both families show an autosomal dominant pattern of inheritance and the mutation segregates with complete penetrance. ATL3 is a paralogue of ATL1, a membrane curvature-generating molecule that is involved in spastic paraplegia and hereditary sensory neuropathy. ATL3 proteins are enriched in three-way junctions, branch points of the endoplasmic reticulum that connect membranous tubules to a continuous network. Mutant ATL3 p.Tyr192Cys fails to localize to branch points, but instead disrupts the structure of the tubular endoplasmic reticulum, suggesting that the mutation exerts a dominant-negative effect. Identification of ATL3 as novel disease-associated gene exemplifies that long-term sensory neuronal maintenance critically depends on the structural organisation of the endoplasmic reticulum. It emphasizes that alterations in membrane shaping-proteins are one of the major emerging pathways in axonal degeneration and suggests that this group of molecules should be considered in neuroprotective strategies.

A disease causing ATLASTIN 3 mutation affects multiple endoplasmic reticulum-related pathways

“…As published before [11], ATL3 localizes predominantly to ER 3WJs, whereas the Y192C variant is distributed along a misshaped ER with much less 3WJs. Untagged as well as N- and C-terminally myc-tagged ATL3 localize to 3WJs (Figure S1a), confirming previous reports [7, 11, 17] and demonstrating that the tag does not interfere with localization. Expression levels of ATL3 and ATL3 Y192C are comparable, suggesting that no differences in expression levels cause the different phenotypes (Fig.…”

“…For construction of untagged human ATL3, ATL3 was amplified from hATL3-myc pCI neo [11] using forward (fwd) primer 5′-ggatccATGTTGTCCCCTCAGCGAGTGG-3′, introducing a Bam HI site and reverse (rev) primer 5′-gcggccgcCTATTGAGCTTTTTTATCCATGGATGGTCTTCC-3′, introducing a stop codon and a Not I restriction site. For construction of N-terminal myc-tagged human ATL3, ATL3 was amplified from hATL3-myc pCI neo using primers fwd 5′-ggatccATGGAACAAAAACTTATTTCTGAAGAAGATCTGTTGTCCCCTCAGCGAGTGG-3′, introducing a N-terminal myc-tag and a Bam HI site and rev: 5′-gcggccgcCTATTGAGCTTTTTTATCCATGGATGGTCTTCC-3′, introducing a stop codon and a Not I restriction site.…”

“…10% of autosomal-dominant pure/uncomplicated forms of HSP [9] and in rare cases of HSAN1 [10]. Two heterozygous mutations causing HSAN were described in ATL3, Y192C [11] and P338R [12]. Both mutations are defective in dimerization and fusion, resulting in aberrant bundling of ER tubules [13].…”

“…Mammalian ATLs differ in tissue expression, with ATL1 being mainly expressed in the CNS [8, 15] whereas ATL2 and ATL3 are more ubiquitously expressed [16]. All ATLs localize to the ER, ATL1 throughout ER tubules, ATL2 and 3 more concentrated to three-way-junctions (3WJs) [7, 11, 17]. …”

Target-enrichment sequencing and copy number evaluation in inherited polyneuropathy

“…16 The discoveries from WES have also broadened gene-specific phenotypes. 17,18 Despite the benefits, the current use of WES as a routine clinical test in polyneuropathy is suboptimal because of its performance metrics (such as depth of coverage), cost, and the difficulty in analysis. Furthermore, complex strategies in reporting and consenting individuals undergoing WES or whole genome sequencing are needed to address ethical issues when unexpected mutations are found in genes unrelated to the disease.…”