Biomaterial Database

Hereditary spastic paraplegia SPG4: what is known and not known about the disease. 2015

Joanna M Solowska, and Peter W Baas

Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, PA 19129, USA.

Mutations in more than 70 distinct loci and more than 50 mutated gene products have been identified in patients with hereditary spastic paraplegias, a diverse group of neurological disorders characterized predominantly, but not exclusively, by progressive lower limb spasticity and weakness resulting from distal degeneration of corticospinal tract axons. Mutations in the SPAST (previously known as SPG4) gene that encodes the microtubule-severing protein called spastin, are the most common cause of the disease. The aetiology of the disease is poorly understood, but partial loss of microtubule-severing activity resulting from inactivating mutations in one SPAST allele is the most postulated explanation. Microtubule severing is important for regulating various aspects of the microtubule array, including microtubule number, length, and mobility. In addition, higher numbers of dynamic plus-ends of microtubules, resulting from microtubule-severing events, may play a role in endosomal tubulation and fission. Even so, there is growing evidence that decreased severing of microtubules does not fully explain HSP-SPG4. The presence of two translation initiation codons in SPAST allows synthesis of two spastin isoforms: a full-length isoform called M1 and a slightly shorter isoform called M87. M87 is more abundant in both neuronal and non-neuronal tissues. Studies on rodents suggest that M1 is only readily detected in adult spinal cord, which is where nerve degeneration mainly occurs in humans with HSP-SPG4. M1, due to its hydrophobic N-terminal domain not shared by M87, may insert into endoplasmic reticulum membrane, and together with reticulons, atlastin and REEP1, may play a role in the morphogenesis of this organelle. Some mutated spastins may act in dominant-negative fashion to lower microtubule-severing activity, but others have detrimental effects on neurons without further lowering microtubule severing. The observed adverse effects on microtubule dynamics, axonal transport, endoplasmic reticulum, and endosomal trafficking are likely caused not only by diminished severing of microtubules, but also by neurotoxicity of mutant spastin proteins, chiefly M1. Some large deletions in SPAST might also affect the function of adjacent genes, further complicating the aetiology of the disease.

UI	MeSH Term	Description	Entries
D009154	Mutation	Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.	Mutations
D004195	Disease Models, Animal	Naturally-occurring or experimentally-induced animal diseases with pathological processes analogous to human diseases.	Animal Disease Model,Animal Disease Models,Disease Model, Animal
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000074181	Spastin	An AAA ATPase that binds and severs MICROTUBULES. It specifically recognizes and cuts polyglutamylated microtubules with short polyglutamate tails to promote reorganization of cellular microtubule arrays and the release of microtubules from the CENTROSOME following nucleation. It is critical for the biogenesis and maintenance of complex microtubule arrays in AXONS; SPINDLE APPARATUS; and CILIA. Mutations in the spastin gene (SPAST) are associated with type 4 of HEREDITARY SPASTIC PARAPLEGIA.	Spastic Paraplegia 4 Protein
D000251	Adenosine Triphosphatases	A group of enzymes which catalyze the hydrolysis of ATP. The hydrolysis reaction is usually coupled with another function such as transporting Ca(2+) across a membrane. These enzymes may be dependent on Ca(2+), Mg(2+), anions, H+, or DNA.	ATPases,Adenosinetriphosphatase,ATPase,ATPase, DNA-Dependent,Adenosine Triphosphatase,DNA-Dependent ATPase,DNA-Dependent Adenosinetriphosphatases,ATPase, DNA Dependent,Adenosinetriphosphatases, DNA-Dependent,DNA Dependent ATPase,DNA Dependent Adenosinetriphosphatases,Triphosphatase, Adenosine
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001370	Axonal Transport	The directed transport of ORGANELLES and molecules along nerve cell AXONS. Transport can be anterograde (from the cell body) or retrograde (toward the cell body). (Alberts et al., Molecular Biology of the Cell, 3d ed, pG3)	Axoplasmic Flow,Axoplasmic Transport,Axoplasmic Streaming,Axonal Transports,Axoplasmic Flows,Axoplasmic Transports,Streaming, Axoplasmic,Transport, Axonal,Transport, Axoplasmic,Transports, Axonal,Transports, Axoplasmic
D015419	Spastic Paraplegia, Hereditary	A group of inherited diseases that share similar phenotypes but are genetically diverse. Different genetic loci for autosomal recessive, autosomal dominant, and x-linked forms of hereditary spastic paraplegia have been identified. Clinically, patients present with slowly progressive distal limb weakness and lower extremity spasticity. Peripheral sensory neurons may be affected in the later stages of the disease. (J Neurol Neurosurg Psychiatry 1998 Jan;64(1):61-6; Curr Opin Neurol 1997 Aug;10(4):313-8)	Hereditary Spastic Paraplegia,X-Linked, Spastic Paraplegia, Hereditary,Autosomal Dominant Hereditary Spastic Paraplegia,Autosomal Dominant Spastic Paraplegia Hereditary,Autosomal Recessive Hereditary Spastic Paraplegia,Autosomal Recessive Spastic Paraplegia, Hereditary,CMT with Pyramidal Features,Charcot-Marie-Tooth Disease with Pyramidal Features, Autosomal Dominant,HMSN 5,HMSN Type V,HMSN V,HMSN V (Hereditary Motor and Sensory Neuropathy Type V),Hereditary Autosomal Dominant Spastic Paraplegia,Hereditary Autosomal Recessive Spastic Paraplegia,Hereditary Motor And Sensory Neuropathy V,Hereditary Motor and Sensory Neuropathy 5,Hereditary Motor-Sensory Neuropathy with Pyramidal Signs,Hereditary Spastic Paraplegia, Autosomal Recessive,Hereditary X-Linked Recessive Spastic Paraplegia,Hereditary, Spastic Paraplegia, Autosomal Dominant,Hereditary, Spastic Paraplegia, X-Linked Recessive,Hypertrophic Motor-Sensory Neuropathy-Spastic Paraplegia,Paraplegia, Spastic, Hereditary,Peroneal Muscular Atrophy with Pyramidal Features, Autosomal Dominant,Spastic Paraplegia 2,Spastic Paraplegia Type 2,Spastic Paraplegia, Autosomal Dominant, Hereditary,Spastic Paraplegia, Autosomal Recessive, Hereditary,Spastic Paraplegia, Hereditary, Autosomal Dominant,Spastic Paraplegia, Hereditary, Autosomal Recessive,Spastic Paraplegia, Hereditary, X-Linked Recessive,Spastic Paraplegia, X-Linked Recessive, Hereditary,Spastic Paraplegia-Hypertrophic Motor-Sensory Neuropathy,Type V Hereditary Motor and Sensory Neuropathy,X Linked Recessive Hereditary Spastic Paraplegia,X-linked Recessive Hereditary Spastic Paraplegia,Charcot Marie Tooth Disease with Pyramidal Features, Autosomal Dominant,Hereditary Motor Sensory Neuropathy with Pyramidal Signs,Hereditary Spastic Paraplegias,Hereditary X Linked Recessive Spastic Paraplegia,Hypertrophic Motor Sensory Neuropathy Spastic Paraplegia,Paraplegia, Hereditary Spastic,Paraplegias, Hereditary Spastic,Spastic Paraplegia Hypertrophic Motor Sensory Neuropathy,Spastic Paraplegias, Hereditary,Type V, HMSN